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GCE O LEVEL SYLLABUS 2010
CHEMISTRY (5070)
Name: _____________________________________ Date: ____________
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=CHAPTER 1 – EXPERIMENTAL CHEMISTRY
1
...
- Conical flask hold approximate volume of 100 cm3 and 250 cm3
...
- Reading to be taken nearer to the meniscus (bottom line)
...
0 cm3 as the ‘0’ means accurate to
0
...
- Burette has long scale of 0 – 50 cm3, accurate to 0
...
- Liquid level to be measured before and after tap opening
...
- Bulb pipette measures exact volumes such as 20
...
0 or 50
...
0 cm3
...
2 types are:
a) Mercury-in-glass
b) Alcohol-in-glass
SI Unit: Kelvin (K)
Daily life measurement: degree Celcius (oC)
K = oC + 273
Time
SI Unit: seconds (s)
Other Units: minutes (min)/hour (h)
Measured with:
(a) Clock
(b) Digital stopwatch
Mass
Mass – the measure of amount of matter in a substance
SI Unit: kilogram (kg)
Other Units: grams (g)/milligrams (mg)
Large volume measurements: tonnes (t)
1 tonne = 1 000 kg
Measured with:
(a) Electric “top-pan” balance
(b) Triple beam balance
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1
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g: white sugar, copper sulfate crystals, distilled water
Mixture – contains two or more substances
...
E
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2 Obtaining Pure Substances
Purification – The seperation process of mixtures into pure substances by using
physical methods without chemical reactions
...
- Mixture is poured through a filter with tiny holes made of paper
...
Crystallisation & Evaporation to Dryness
Crystallisation – separation of dissolved solid from a solution as well-formed
crystals
Evaporation to Dryness – seperation of dissolved solid from a solution as crystals of
salt by evaporating all the liquid off
...
Sublimation
Sublimation – separation of a mixture of solids which one of it sublimes (by heating
the solid mixture to turn one of the substance into vapour without going through
liquid state)
...
studyguide
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The steam is cooled in
condenser to form pure liquid
...
Fractional Distillation
Fractional Distillation – separates mixture of miscible (soluble) liquids with widely
differing boiling points
...
g
...
Ethanol with lower
boiling point boils and vaporises first and reach fractionating column then cools
and condenses into ethanol as it passes through condenser
...
Water will distil the same way after all ethanol
is distilled
...
g
...
studyguide
...
Some salt particles may still pass through
...
To separate, take the
stopper off and turn the tap on to run the denser liquid
at the bottom off the funnel and leave the less dense
liquid in the funnel by turning the tap off and reset the
stopper at its original position
...
The need for Chromatography
- Separates and identify mixtures of coloured substances in dyes
- Separates substances in urine, drugs & blood for medicinal uses
- To find out whether athletes have been using banned drugs
Separating Mixtures of Coloured Substances
Obtain a dye sample then put a drop of the sample on a pencil line drawn on the
filter paper then dip the paper into a solvent with the level below the spot
...
Hence they are
separated
...
The result
shows that:
- The sample dye is made of 3 colours
...
- a comparison dye isn’t part of sample
...
Locating Agent – a substance that reacts with substances (e
...
sugars) on paper to
procuce a coloured product
...
Pure water boils at 100oC and melts at 0oC
...
They melt and
boil at a RANGE OF TEMPERATURES
e
...
starts boil at 70oC, completes boil at 78oC
Also, it can VARY melting and boiling points of pure substances
...
g
...
3 Identification of Ions and Gases
Refer to Insert 1
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END OF CHAPTER 1
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CHAPTER 2 – THE PARTICULATE NATURE OF MATTER
2
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Three forms – solids, liquids,
gas
...
Another jar full of air
is placed on top of jar with bromine, separated with
cover
...
Explanation:
Bromine particles move from lower jar into spaces between air particles in upper
jar
...
Eventually, bromine and air particles are mixed completely
...
CuSO4 crystals placed in beaker of water, blue
particles of the crystals is spread throughout
the water to form uniformly blue solution
...
NH4OH vapor and HCl vapor diffuses in
the tube and a compound is produced inside the tube closer to HCl soaked
cotton as the particles are heavier
...
The smaller mass, the faster particles diffuse
...
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...
1
...
g
...
2
...
The temperature is
due to speed of movement of particles
...
3
...
They increase distance
between particles during expansion
...
The temperature at which solid melts is melting point
...
B-C: the temperature remains constant as heat is
absorbed to break forces of attraction instead for
raising temperature
...
C-D: liquid heats as heat energy increases temperature
...
Freezing point is the temperature at which liquid freezes
...
B-C: heat energy is released as particles slow down to
take up fixed and orderly position of a solid
...
C-D: solid cools to the temperature of surroundings
...
Boiling point is the temperature at which liquid boils
...
B-C: heat energy is absorbed by particles to break the
attractive forces so that they move freely and far
apart as gas particles
...
It gives cooling effect – heat energy absorbed from surroundings
...
Heat energy is given out as gas
particles slow down and move closer to one another to form liquid
...
Heat is absorbed
...
studyguide
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2 Atomic Structure
Atoms contain PROTONS, NEUTRONS, and ELECTRONS
Protons have positive charge while neutrons has neutral charge but same mass as
protons
...
Particle
Symbol
Relative mass
Charge
Proton
p
1
+1
Neutron
n
1
0
Electron
e–
-1
Protons and neutrons are located in nucleus
...
Electrons move around nucleus in an orbit called electron shells
...
NUCLEON NUMBER is the number of protons and neutrons in nucleus of an atom
...
e
...
ISOTOPES are atoms of the same element with different number of neutrons
...
E
...
Hydrogen atoms has 3 isotopes, ,
and
...
First shell contains maximum 2 electrons
...
To write electronic configuration we write as n
...
n
...
E
...
Sulfur has electronic configuration of 2
...
6
The valence electrons is the number of electrons of the outermost shell
...
Relation with Periodic Table
Elements in same horizontal row: Period
Elements in same vertical column: Group
Group 1 has 1 valency, Group 2 has 2 valency, Group 3 has 3 valency and so on
...
Down the period the number of shells increases
...
studyguide
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3 Structure and Properties of Materials
Elements
Element is a substance that cannot be broken down into simpler substances by
chemical nor physical methods
...
g
...
Classifying Elements
- Classifying by state
...
g
...
- Classifying by metals and non-metals
...
g
...
From left-right elements change from metal to non-metal
COMPOSITION OF ELEMENTS
Elements are made of atoms
Atom is smallest unit of an element, having properties of that element
...
g
...
g
...
2
...
Ionic bonds are formed between METALLIC and NON- METALLIC ATOMS ONLY
...
E
...
Formation of NaCl
Compounds
Compound is substance containing 2 or more elements chemically joined together
e
...
Magnesium is an element; oxygen is an element – they can only be burnt to
form magnesium oxide compound
...
g
...
Mixtures
Mixture contains 2 or more substances not chemically joined together
...
The loss of electron forms cation, Na+, and the gain of electron
forms anion, Cl-
...
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Formation of MgF2
STRUCTURE AND PROPERTIES OF IONIC BONDS
Structure
Ionic substances appear as giant lattice structures which
the ions are held together by electrostatic force
between oppositely charged ions
...
E
...
in sodium chloride, the ratio
Na:Cl is 1:1, therefore the ionic formula is NaCl
...
The loss of electron forms cation, Mg2+, as it loses 2
electrons, and the gain of electron forms anion, F-
...
Properties
1
...
2
...
3
...
Hence, ionic compounds have no smell
...
Solid ionic compounds don’t conduct electricity but they do when they are
aqueous or molten
...
In solids, these ions are fixed in place
...
Ionic compounds are soluble in water but insoluble in organic compounds
...
Vice versa is when in organic solvent
...
Group
I to group III elements has charge of +1, increasing to +3, going to the right
...
E
...
Aluminium sulfate
We have to balance the charges to make a stable bond
Ions present: Al3+
SO42Al3+
SO42SO42Total change: 6+
6Therefore, the formula is Al2(SO4)3
1
...
g
...
Polyatomic ion should be placed in brackets, e
...
Fe(NO3)2
2
...
Covalent bonds occur between NON-METALLIC ATOMS ONLY
...
THE SHARED ELECTRONS APPEAR IN PAIRS!
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H2 molecule
Hydrogen atom has one valency
...
When 2 hydrogen atoms
join, they share their electrons, on which, the share becomes 2 electrons, which is
now a noble gas configuration, being shared between these 2 atoms
...
E
...
Cl2 molecule
E
...
H2O molecule
Apart from oxygen sharing between oxygen atoms, it can have electrons with other
atoms
...
Each hydrogen with oxygen atom form a single bond: O – H
...
g
...
Hence they share an electron EACH to hence
share 2 electrons between the atoms
...
E
...
O2 molecule
An O atom has 6 valency and needs 2 electrons, each, to form a noble gas
configuration
...
The contribution hence now
become 4 electrons and what left on each oxygen atom is 4 electrons
...
We share two from oxygen part, WHICH HAS THE
SMALLEST NUMBER OF SHORT ELECTRONS, TO SHARE THE AMOUNT OF
ELECTRONS THAT ATOM NEEDS, to form 4 shared atoms
...
The atoms are now stable and since each bond has 2 pairs of electrons, we
call this double bond: C = O
...
Two pairs of shared electrons between 2 atoms forms DOUBLE BOND, X = Y
...
This information is important when you want to know the bond forces between
atoms in exothermic/endothermic reactions
...
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Silicon Dioxide
Silicon dioxide, SiO2, has silicon atoms bonded with another oxygen atoms in a
tetrahedral arrangement which each silicon atom uses all its valence electrons to
form 4 single covalent bonds with other 4 oxygen atoms
...
Properties
1
...
This property makes it suitable as abrasives
...
It has very high melting and boiling points
...
It does not conduct electricity (except graphite) because there are no free
electrons in covalent bonds since they are used to form bonds; hence electrons
are in fixed positions
...
4
...
2
...
The
atoms are packed closely together in giant lattice structures
...
There are free
electrons moving between the spaces and positive metal ions are attracted to the
sea of electrons which hold the atoms together
...
Metals can be bent (ductile) and can be stretched (malleable) because the
layers of atoms in metals slide over each other when force is applied but will
not break due to attractive force between electrons and metal ions
...
Metals conduct electricity as it has free electrons which carries current
...
Metals conduct heat as it has free electrons which gains energy when heated
and moves faster to collide with metal atoms, releasing heat in collisions
...
Metals have high melting and boiling points because the bonds between
metals is very strong
...
2
...
Simple molecular substances are usually liquids/gases at r
...
p
...
2
...
3
...
4
...
5
...
END OF CHAPTER 2
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CHAPTER 3 – FORMULAE, STOICHIOMETRY AND THE MOLE CONCEPT
3
...
The mass of the isotope is
Mr(Fe2O3) = 2(56) + 3(16) = 160
12 times greater than hydrogen atom so
= 70%
Mr(Fe3O4) = 3(56) + 4(16) = 232
of carbon-12 atoms is equivalent to the
mass of one hydrogen atom
...
3
...
g
...
Relative Molecular Mass – the average mass of one molecule of substance
(averaging isotopes) when compared with
mass of a carbon-12 atom
...
g
...
3 Percentage Composition
e
...
Determine which oxides of iron of Fe2O3 or Fe3O4 has more iron
...
Ar =
x 100 %
x 100 %
=
x 100%
= 72%
Fe3O4 has more iron composition than that of Fe2O3
...
The percentage mass of iron in
iron(III) oxide is 70%
...
7 x 200)g = 140g
e
...
Determine the mass of iron in 200g of Fe2O3
...
e
...
Calculate water mass in 12
...
5g
MOLE
3
...
5g
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g
...
Find the number of moles Argon atom in 6
...
n (HArF) =
n=
e
...
111 mol
n (Ar) = 0
...
111 mol
n=
= 5 mol
e
...
25 mole of CO2
...
25mol =
Number of particles = 0
...
5 x 1023 molecules
Number of atoms = total number of atoms in CO2 x noumber of particles
= 3 x 1
...
5 x 1023 atoms
3
...
Eg
...
Eg
...
Eg
...
5, molar mass= 58
...
g
...
4 mol of iron atom
...
7 Different Kinds of Chemical Formulae
Ethene formula is C2H6
Molecular Formula – shows the actual formula and kinds of atoms present, e
...
C2H6
Empirical Formula – shows the simplest whole number ratio of the atoms present,
e
...
C2H6, ratio 1:3, therefore C1H3, simply CH3
Structural Formula – shows how atoms are joined in the molecule
...
Ball-and-Stick
Diagrammatic
Calculating the Empirical Formula of a Compound
Find the empirical formula of an oxide of magnesium consisting of 0
...
96g of magnesium
...
n(Mg) =
n(O) =
= 0
...
02 mol
Step 2: Divide the moles by the smallest number
...
4 x 56 = 22
...
studyguide
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Take the total 100% to be 100g
...
e
...
What is the number of moles of 240cm3 of Cl2 at r
...
p
...
01 mol
Molar Volume and Molar Mass
Gases have same volume but not necessarily same mass
Example: Hydrogen -> 2g, Carbon Dioxide -> 44g
n(O) =
= 1
...
75 mol
Step 2: Divide the moles by the smallest number
...
g
...
t
...
Step 1: Find the number of moles from the mass of nitrogen
n=
From Empirical formula to Molecular Formula
Find the molecular formula of propene, CH2, having molecular mass of 42
...
8 Molar Volume of Gases
The Avogadro’s Law
Equal volume of gases at same temperature and volume contain equal number of
particles or molecules
...
t
...
) = 24dm3
1dm3 = 1000cm3
Formulae:
Number of moles of a gas (n) =
Volume of a gas = Number of moles (n) x Molar volume (Mr)
= 0
...
25 mol =
Volume of gas = 0
...
9 Concentration of Solutions
Concentration of solution tells the number of solute in a volume of solution
(
Concentration (C) =
)
(
)
Calculating the Amount of Solute
Moles of solute (n) = Concentration (
e
...
What is the mass of solute in 600cm3 of 1
...
60 dm
n = 1
...
60
= 0
...
9 =
m = 0
...
studyguide
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10 Constructing Chemical Equations
E
...
1: Reaction Between Hydrogen and Oxygen
Word Equation: Oxygen + Hydrogen Water
To write the chemical equation, we use symbols of atoms/molecules:
O2 + H2 H2O
BUT THIS IS IMBALANCED! A BALANCED EQUATION MUST HAVE THE SAME
NUMBER OF ATOMS OF EACH ELEMENTS ON BOTH SIDES! THEREFORE
...
Therefore we multiply
product by 2 first
...
O2 + H2 2H2O
O H
H
O H
H
H
H
O
O
Now we can cancel off oxygen atoms
...
Therefore, we multiply the hydrogen molecule by 2 so that the short
is balanced
...
O2 + 2H2 2H2O
O H
H
O H
H
H
H
H
H
O
O
3
...
Suppose we want to find
moles of X atoms that reacted to form 0
...
We always put the
atom we want to find as numerator and the denominator being the atom we know
...
g
...
of moles of Y to find the reacting mole of X
...
25 = 0
...
125 mole of X reacted with 0
...
To find the reacting mass of
X, e
...
Y is given as 35g, we just multiply the mole by the mass of Y as they are
always in ratio:
0
...
375 g
Reacting Masses and Volumes
First, find the ratio of moles and multiply the mole of the gas volume you want to
find with the volume of gas at room temperature (24dm3)
Example
MgCl2 is formed by reacting Mg and HCl according to equation:
Mg(s) + 2HCl(aq) MgCl2(s) + H2(g)
Find the amount of hydrogen gas, in cm3, formed when 14
...
Ratio:
=
m(HCl) =
=0
...
4 = 0
...
t
...
= 0
...
8 dm3
1dm3 = 1000cm3
4
...
studyguide
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12 Introductory Chemical Analysis
Analysis is finding out what a substance or product is made of
Chemical analyst is the person who does chemical analysis
2 kinds of chemical analysis:
- Qualitative analysis
is the identification of elements/compounds present in an unknown substance
- Quantitative analysis
Is the meaurement of concentration of elements/compunds in unknown substance
3
...
Ammonium compounds and compounds in Groups I and II are white solids that
dissolve in water to form colourless solutions
Copper(II) compounds are blue/green (except CuO is black)
Iron(II) compounds are pale green, iron (III) compounds are red or yellowish
Chlorine gas is greenish-yellow
...
14 Volumetric Analysis
Is a measure of concentrations of acids/alkalis in solutions
Acid-alkali Titrations in Volumetric Analysis
It needs: - a standard solution: a solution of known concentration, and
- a solution of unknown concentration
Detecting the End Point
End point is the point at which neutralisation of acid and alkali is complete
- Sharp indicators (phenolphtalein and methyl orange) are used to detect end
point effectively
- Litmus and universal indicators isn’t used as the changes of end point isn’t sharp
A Typical Acid-alkali Titration
The diagram shows how titration is used to find concentration of H2SO4 using NaOH
- Smell
Gases like oxygen, hydrogen and carbon dioxide are odourless
Others like chlorine, ammonia and sulphur dioxide have characteristic smells
- Solubility in Water
Some substances like AgCl and CaSO4 are insoluble while other does
- pH
If a substance is pH 1 or 2, all alkaline and weakly acidic substances couldn’t be
the substance
...
studyguide
...
0 cm3 of 0
...
0 cm3 of H2SO4 in a
titration
...
100 x
mol
Step 2: Write the chemical equation for the reaction
2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2H2O(l)
Step 3: Find the ratio of number of moles of H2SO4 to number of moles of NaOH
=
Step 4: Use ratio to find number of moles of H2SO4 that reacted
Example:
25
...
5 cm3 of 0
...
Calculate the concentration of FeSO4(aq)
Step 1: Find the reacting mole of KMnO4
n(KMnO4) = Concentration x Volume in mol/dm3
= 0
...
0015 mol
Step 5: Find the concentration of H2SO4 in mol/dm3
= 5 x 0
...
00275 mol x
= 0
...
0015 mol x
Other Titrations
To find the concentration of a solution of FeSO4 using KMnO4 is as below
mol
= 0
...
06 mol/dm3
=
Step 4: Use ratio to find number of moles of FeSO4 that reacted
n(FeSO4) = 5 x number of moles of NaOH
n(H2SO4) = x number of moles of NaOH
= x 0
...
15 Uses of Titrations in Analysis
Identification of Acids and Alkalis
Example:
An acid has formula of H2XO4
...
A
solution of the acid contain 5
...
In titration, 25
...
5cm3 of 0
...
Calculate the concentration of acid in mol/dm3
and find X of the acid and its identity
n(NaOH) = Concentration x Volume in mol/dm3
= 0
...
studyguide
...
01 x
∴ Concentration =
= x 0
...
051 mol/dm
Since 1 dm of H2XO4 contains 0
...
∴ 0
...
0 g/dm3of FeSO4 xH2O
...
0 cm3 of Y reacted
with 27
...
02 mol/dm3 KMnO4
...
Calculate the concentration of Y in mol/dm3 and the value of x
...
02 x
mol
Ratio of FeSO4 xH2O to KMnO4 according to question; find mole according to ratio
Hence, Mr of X = 98 – 2(1) – 4(16) = 32
...
02 x
∴ Concentration =
Percentage purity =
Example:
5 g of impure sulphuric acid is dissolved in 1 dm3 of water
...
0 cm3 of the solution
required 23
...
1 mol/dm3 NaOH for complete titration reaction
...
n(NaOH) = Concentration x Volume in mol/dm3
= 0
...
1 x
∴ Concentration =
= x 0
...
2%
x
= 0
...
108 mol FeSO4 xH2O = 30
...
0 cm3 of 0
...
0 cm3 of 0
...
Find the values of x and y given the equation:
xH2O2 + yKMnO4 + acid → products
n(H2O2) = Concentration x Volume in mol/dm3
= 0
...
047 mol/ dm3
Hence mass of H2SO4 in 1 dm3 = 0
...
047 x 98g
= 4
...
02 x
mol = 0
...
02 x
Therefore 1 mole KMnO4 react with
mol = 0
...
5 moles of H2O2
Hence ratio of x:y is 2
...
studyguide
...
1 Introductory Electrolysis
Electrolysis is the decomposition of compound using electricity
When molten binary compound is electrolysed, metal is formed on cathode while
non-metal is formed on anode
...
To
electrolyse it, pass current through the molten PbBr2
...
Electrode is a rod or plate where electricity enters or leaves electrolyte during
electrolysis
...
Discharge is the removal of elctrons from negative ions to form atoms or the gain
of electrons of positive ions to become atoms
...
c
...
Oxidation
occurs here
...
This causes anion to discharge its electrons here
to replace lost electrons and also, negativecharge are attracted to positive charge
...
c
...
Reduction occurs here
...
This causes
cation to be attracted and gains electrons to be an atom
...
It’s attracted to anode
...
It’s attracted to cathode
...
2 Electrolysis of Molten Compounds
Molten/aqueous ionic compounds conduct electricity because ions free to move
...
Hence
solid ionic compounds do not conduct electricity
...
Br
atoms created form bond together to make Br2 gas
...
Pb2+(aq) + 2e- Pb(l)
Overall Equation
PbBr2(l) Pb(l) + Br2(g)
Below are other compounds that can be electrolysed
...
Molten electrolyte
Cathode product
Anode product
Calcium chloride (CaCl2)
Calcium, Ca
Chlorine, Cl2
Sodium chloride (NaCl)
Sodium, Na
Chlorine, Cl2
Aluminium(III) oxide (Al2O3)
Aluminium, Al
Oxygen, O2
Sodium Iodide (NaI)
Sodium, Na
Iodine, I2
4
...
Only 2 of these are discharged
...
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At cathode
- In CONCENTRATED solutions of nickel/lead compound, nickel/lead will be
discharged instead of hydrogen ions of water which is less reactive than
nickel/lead
...
- Reactive ions (potassium, sodium, calcium, magnesium, aluminium) will NEVER
BE DISCHARGED in either concentrated or dilute condition
...
At anode
- In CONCENTRATED solutions, iodine/chlorine/bromine ions are preferrable to be
discharged, although it’s harder to discharged compared to hydroxide ions
...
- Sulphate and nitrate are NEVER DISCHARGED in concentrated/dilute solutions
...
Cl atoms created form covalent bond together to make Cl2 gas
...
2H+(aq) + 2e- H2(l)
Overall Equation
2HCl(l) H2(l) + Cl2(g)
Note: any cation and anion left undischarged in solution forms new bonds between
them
...
g
...
Very Dilute Solutions
Electrolysis of Dilute H2SO4
Ions Present
H+, OH- and SO42Reaction at Anode
OH- loses electrons at anode to become O2 and H2O
...
2H+(aq) + 2e- H2(g)
Overall Equation
Both equations must be balanced first
...
Hence, we should first even them by multiplying cathode equation by 2
...
studyguide
...
Hence:
4H2O(l) 2H2(g) + O2(g)+ 2H2O(l)
H2O molecules are formed on both sides
...
4
...
Examples are platinum and graphite
...
Example is copper
...
g
...
4OH -(aq) O2(g)+ 2H2O(l) +4eReaction at Cathode
Cu2+ gains electrons at cathode to become Cu atoms becoming liquid copper
...
Cu2+(aq) + 2e- Cu(s)
Overall Equation
Both equations must be balanced first
...
Hence, we should first even them by multiplying cathode equation by 2
...
Hydrogen and
sulphate ions left forms sulphuric acid
...
g
...
Instead, the copper
anode discharged by losing electrons to form Cu2+
...
Cu(s) Cu2+(aq) + 2eReaction at Cathode
Cu2+ produced from anode gains electrons at cathode to become Cu atoms
becoming copper
...
Cu2+(aq) + 2e- Cu(s)
Overall Change
There is no change in solution contents as for every lost of Cu2+ ions at cathode is
replaced by Cu2+ ions released by dissolving anode
...
We can use this
method to create pure copper on cathode by using pure copper on cathode and
impure copper on anode
...
4
...
This
makes the object protected and more attractive
...
studyguide
...
The electrolyte MUST contain plating metal cation
...
So,
the electrode size decreases
...
Hence, the nickel is deposited here
and the electrode grows
...
Uses of Electroplating
Plating Metal
Uses
Chromium
Water taps, motorcar bumpers, bicycle parts
Tin
Tin cans
Silver
Silver sports trophies, plaques, ornaments, cutleries
Nickel
For corrosion-resistant layer
Gold
Watches, plaques, cutleries, water taps, ornaments
Rhodium
Silverware, jewellery, watches, ornaments
Copper
Printed circuit boards, trophies, ornaments
4
...
The cathode is made of more
reactive metal
...
The anode is made of less reactive
metal
...
How the Voltage is Produced
Use an example of zinc and copper as electrodes and sodium chloride as electrolyte
As zinc is more reactive, it is cathode while copper is anode
...
The electrons flow against
conventional current towards copper anode
...
2H+(aq) + 2e- H2(g)
Hence the overall ionic equation is:
Zn(s) + 2H+(aq) Zn2+(aq) + H2(g)
which comes from the equation:
Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)
END OF CHAPTER 4
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CHAPTER 5 – ENERGY FROM CHEMICALS
5
...
This is to form bonds
between the reactants which needs less energy in them
...
Changes of State
When gas condenses to water or water freezes to solid, heat is given out
...
Combustion reactions
All combustion (burning) reactions are exothermic
...
Dissolving of anhydrous salts/acids in water
Dissolving solid salt to aqueous solution of the salt gives out heat
Dissolving of Na2CO3 in water (or CuSO4)
Na2CO3(s) → Na2CO3(l) + heat
Dissolving of concentrated acid in water
HCl(aq) + H2O(l) → less concentrated HCl(aq) + heat
4
...
Metal Displacement
Magnesium reacting with copper(II) sulphate
Mg(s) + Cu2+(aq) → Mg2+(s) + Cu(s) + heat
5
...
This is to break bonds
between the reactants which needs more energy in them
...
Changes of states
When solid melts to water & boils to steam, heat is absorbed to break the bond
...
Photolysis
Reaction of light sensitive silver chloride in camera reel in light
2AgBr(s) + heat → 2Ag(s) + Br2(g)
3
...
NH4Cl(s) + heat → NH4Cl(aq)
CuSO4(s) + heat → CuSO4(aq)
4
...
5
...
g
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Acid + Bicarbonates (HCO3)
NaHCO3(s) + H2SO4(aq) + heat → NaSO4(aq) + CO2(g) + H2O(l)
Acid Spill Treatment on Body
We don’t neutralize spilled acid on body as it produces heat
...
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5
...
The symbol is ∆H measured in kilojoules(kJ)
...
Endothermic reaction:
CaCO3(s) → CO2(g) + CaO(s) [∆H = +222 kJ]
222 kJ of heat energy is absorbed when 1 mol of CaCO3 decompose to 1 mol of
CO2 and 1 mol of CaO
...
4 Heat Energy and Enthalpy Change in Reaction
When bonds made, heat energy is given out, it’s exothermic and ∆H is negative
When bonds broken, heat energy is absorbed, it’s endothermic and ∆H is positive
Question:
Hydrogen bromide is made by reacting H2 gas with Br2 gas
...
H2(g) + Br2(g) → 2HBr(g)
Covalent Bond
Bond energy (kJ/mol)
H–H
436
Br – Br
224
H – Br
366
Bonds of H2 and Br2 molecules must be broken first to make HBr
...
H – H + Br – Br → H H Br Br
Broken bonds are used to make H – Br bonds of HBr
...
H H Br Br → 2H – Br
Heat change can be calculated by:
∆H = heat released in making bonds + heat absorbed in breaking bonds
Exothermic ∆H = the bond energy of 2 H – Br bonds
= 2(366)
= – 732 kJ
Endothermic ∆H = the bond energy of 1 H – H bond + 1 Br – Br bond
= 436 + 224
= + 660 kJ
∆H = – 732 + 660
= – 72 kJ
Therefore more heat is given out in making bond than absorbed in breaking bond
...
Exothermic graph:
When heat is given out, the solution becomes warm and later the temperature
goes back to room temperature
...
5
...
It is the energy needed to break the reactant bonds before new bonds are formed
...
studyguide
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Exothermic and Endothermic Reaction Graph
In exothermic reaction, enough energy given out in the reaction of parcticles to
provide activation energy therefore less energy is needed to form products
...
More energy is needed to form
products and heat must be continually added to fulfill energy requirement
...
CH4(g) + H2O(g) CO(g) + 3H2(g)
The by-product carbon monoxide is not wasted
...
CO(g) + H2O(g) CO2(g) + H2(g)
Now you get more hydrogen
...
5
...
These fuel mainly methane from coal, wood, oil, natural gas & hydrogen
...
Hence, exothermic reaction
...
They are mainly used as rocket fuel
...
However, we don’t use heat
energy for our daily appliances
...
A fuel cell converts chemical energy directly into electrical energy
...
studyguide
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H2 + 2OH- 2H2O + 2eElectrons flows past the load and to the other electrode
...
Hydroxide ions constantly deposit electrons here to make
water
...
Oxygen reacts with water created on from hydrogen on the cathode to gain
electrons from it:
O2 + 2H2O + 4e- 4OHIf we combine the ionic equations, we still get water as product of hydrogen and
oxygen, but the energy produced is now electrical energy:
2H2(g) + O2(g) H2O(g) + electrical energy
Advantages of Fuel Cells
- Electrical energy can be generated continuously if there’s continuous fuel supply
- The by-product of fuel cells is steam, which do not pollute the environment
- Chemical energy is efficiently converted to electrical energy
...
Disadvantages of Fuel Cells
- Hydrogen-oxygen fuel cells are very expensive, hence limiting their use
...
Crude oil, freshly extracted from underground, undergo refining – a process where
oil undergoes fractional distillation to be separated into its fractions
...
The fractionating
column is cooler on top, hence upper trays collects fractions of low boiling points
while the lower ones, being hotter, collect those with higher boiling points
...
13 Fractions and their uses
PHOTOSYNTHESIS AND ENERGY
Plants take in carbon dioxide and water in presence of chlorophyll and synthesize
them in the presence of sunlight to produce glucose and release oxygen:
6CO2 + 6H2O C6H12O6 + 6O2
Plants get their energy by using the glucose formed
...
First, glucose fermented to make ethanol by microorganisms such as yeast
...
The glucose is usually derived from corn plant or sugar cane
...
Some water might still be present as the boiling
point is close to ethanol
...
This is biofuel, and it’s a renewable energy source
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studyguide
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1 Speed of Reaction
Measuring Speed of Reaction
It is the speed for a reactant to be used up or product to be formed
...
- Gradient decreases with time – speed decreases with time
...
The reaction has finished
...
2 ways to find out speed of reaction
1
...
Speed of reaction =
Speed of reaction A =
= 0
...
667/s
Therefore reaction B is faster than reaction A as time
taken for B is shorter
Number of times B faster than A =
= 2 times
2
...
Can be measured by plotting change in volume of gas evolved, mass of reaction
mixture as reaction proceeds and change of pressure of gas formed
...
Consider reaction of limestone with acid to produce carbon dioxide
...
A
graph of volume of gas against time is plotted
...
The reading on balance is
plotted on a graph on every time interval
...
Particle Size of Reactant
When large marble is reacted with acid and compared to reaction of fine marble
solids being reacted with acid and the graph of volume of gas against time is
plotted, it’s found that the reaction involving finer marble chips produces gas
faster than the one with larger marble chunk as the graph of finer chips is
steeper
...
Therefore,
reactions of solids with liquid/gas is faster when the solids are of smaller pieces
...
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Small particles creates larger surface area
for more collisions between reacting particles which increases speed of reaction
...
In coal
mines, when air contains too much coal dust, explosion can occur from a single
spark or match
...
- Flour in mills can ignite easily due to large surface area
...
Concentration of Reactant
In the increase of concentration means there are more solute particles per unit
volume of the solution which favours for more effective collision resulting in an
increase in speed of reaction
...
Pressure of Reactant
Only gaseous reactions are affected as gas is compressible
...
High pressure is used in industrial processes (e
...
Haber Process Plant) so that
the reaction goes faster
...
Temperature of Reaction
Speed of reaction increases when temperature increases
...
With increase in temperature, particles absorb the energy and having
enough activation energy, they move faster and collide more effectively per
second
...
Usually, speed of reaction doubles for every 10oC rise in temperature
...
Effect of Catalyst
What are catalysts?
They are chemical substances which alters speed of reaction without itself being
used at the end of a reaction
...
- transition metals (e
...
Titanium, Nickel, Iron, Copper) are good catalysts
- most catalyst catalyse one kind of reaction (except titanium)
Reaction
Catalyst
Production of sulphur by contact process
Vanadium(V) oxide, V2O5
Production of ammonia by Haber Process
Iron, Fe
Aluminium oxide, Al2O3
Production of hydrogen by cracking of hydrocarbons
Silicon dioxide, SiO2
Production of margarine by reacting hydrogen with
Nickel, Ni
vegetable oil
Production of plastics
Titanium(IV) chloride, TiCl4
Titanium, Ti
Converting CO into CO2 in catalytic converters
Rhodium, Rh
Catalysts lower the need of energy to break bonds so activation energy is lower
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Hydrogen in Reduction-Oxidation reaction
Oxidation is the loss of hydrogen by a substance
Reduction is the gain of hydrogen by a substance
Enzymes
Enzymes are biological catalysts
Characteristics of enzymes:
- They are very specific
...
- Enzymes are sensitive to temperature
...
Too high or too
low temperatures destroy enzymes
...
They function within narrow range of pH
...
These enzymes can be found in papaya fruit
...
Beer, wine
and soy sauce are made this way
...
6
...
Ag2O is oxidizing agent
...
Pb is reducing agent
...
Cl2 is oxidizing agent
...
H2S is reducing agent
...
Cl2 is oxidizing agent
...
Na is reducing agent
...
Reaction of metal + dilute acid
2
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Cu is reducing agent
+
H ions in HCl reduced as it loses oxidation state from +1 to 0
...
Examples of elements with variable oxidation states
-2
Oxidation is the increase of oxidation state by a substance
Reduction is the decrease of oxidation state by a substance
Examples:
Metals with acids
(b) KMnO4
(+1) + (oxidation state of Mn) + (-2) x 4 = 0
(oxidation state of Mn) + (+1) + (-8) = 0
(oxidation state of Mn) + (-7) =0
Oxidation state of Mn = +7
Oxidation
state
Manganese
Chromium
Iron
Sulphur
Carbon
Some compounds with possible variable oxidation states have roman numeral as a
guide about their oxidation state, e
...
- Iron(II) chloride has formula FeCl2 and iron oxidation state +2
- Potassium(VI) dichromate has formula K2Cr2O7 and potassium oxidation state +6
- Manganese(IV) oxide has formula MnO2 and manganese oxidation state +4
+4
+5
+6
MnO2
CrCl3
FeCl3
KMnO4
K2Cr2O7
SO2
CaCO3
+7
H2SO4
Halide (Halogen) Displacement Reactions
Cl2(aq) + 2KI(aq) → 2KCl(aq) + I2(aq)
I ions in KI oxidized as it gains oxidation state from -1 to 0
...
Cl2 is oxidizing agent
Test for Oxidising/Reducing Agents
Name of compound
Potassium dichromate(VI)
Potassium manganate(VII)
Chlorine
Oxidizing agents
Formula
Applications
Test for reducing agent; orange K2Cr2O7
K2Cr2O7
reduces to green Cr3+ ions
Test for reducing agent; purple KMnO4
KMnO4
reduces to colourless Mn2+ ions
Oxidizes Br- to Br2 and I- to I2; greenCl2
yellow Cl2 reduces to colourless Cl- ions
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Name of compound
Potassium Iodide
Carbon monoxide
Hydrogen
Sulfur dioxide
Metals (highly reactive)
33
Reducing agents
Formula
Applications
Test for oxidizing agent; colourless I- ions
KI
oxidizes to brown I2
CO
Reduces metal oxide to metal in heat
H2
Reduces copper(II) oxide to copper
SO4
used as bleach and preservative
Na, Mg, etc
...
This is not a redox reaction
...
This is not a redox reaction
...
This is not redox
...
3 Reversible Reactions
Reversible reactions are denoted by the sign “⇌” where the arrow denotes
forward reaction, where reactants react to form products, and the arrow
denotes backward reaction where products decompose to reform reactants
...
E
...
N2(g) + 3H2(g) ⇌ 2NH3(g)
Effect of Temperature on Reversible Reactions
With higher temperature, the condition is now favored to break the bonds of the
product formed (The bonding of products requires low temperatures)
...
Effect of Pressure on Reversible Reactions
Increase in pressure encourages forward reaction because the higher pressure the
more reactants collide to react
...
Both reactants are reacted and products decompose
at the same rate
...
When we remove the products, it will also encourage forward reaction as the
reaction would try to achieve equilibrium
...
studyguide
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1 The Characteristics of Acids and Bases
Common Acids
Acids in daily life:
Ethanoic acid – found in vinegar and tomato juice
Citric acid – found in citrus foods like lemons, oranges and grapefruit
Lactic acid – found in sour milk and yoghurt, and in muscle respiration
Tartaric acid – found in grapes
Tannic acid – found in tea and ant’s body
Formic acid – found in bee stings
Hydrochloric acid – found in stomach juices
- Acids react with carbonates and hydrogencarbonates (bicarbonates)
Carbon dioxide is to be formed
...
Carbonates:
MgCO3(s) + 2HCl(aq) → MgCl2(aq) + CO2(g) + H2O (l)
Bicarbontes:
NaHCO3(s or aq) + HCl(aq) → NaCl2(aq) + CO2(g) + H2O (l)
Laboratory acids: 3 common laboratory acids
Hydrochloric acid (HCl)
Sulphuric acid (H2SO4)
Nitric acid (HNO3)
Dilute acids – solution containing small amount of acid dissolved in water
Concentration acids – solution containing large amount of acid dissolved in water
Storage of Acids
Acids are stored in claypots, glass or plastic containers as sand, glass and plastic do
not react with acids
...
The gas is tested with a
burning splint which shows hydrogen burns with a ‘pop’ sound
...
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2 Acids and Hydrogen Ions
The Need for Water in Acids
Acids are covalent compounds and do not behave as acids in the absence of water
as water reacts with acids to produce H+ ions, responsible for its acidic properties
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Hydrogen Ions
Hydrogen gas is formed by acids as H+(aq) ions are present in acid solutions
- This means when a solid/gas acid dissolved in water, they produce H+ ions in it
Chemical eqation:
HCl(s) water HCl(aq)
Ionic Equation:
HCl(s) water H+(aq) + Cl-(aq)
*Note that for ionic equation only aqueous solutions are ionised*
- However when dissolved in organic solutions, they don’t show acidic properties
When metals react with acids, only the hydrogen ions react with metals, e
...
:
Chemical equation:
2Na(s) + 2HCl(aq) → 2NaCl(aq) + H2(g)
Ionic equation:
2Na(s) + 2H+(aq) → 2Na+(aq) + H2(g)
Basicity of an acid is maximum number of H+ ions produced by a molecule of acid
Some Acids With Their Basicity
Acids
Reaction with water
Basicity
Hydrochloric acid
HCl(aq) → H+(aq) + Cl-(aq)
monobasic
Nitric acid
HNO3(aq) → H+(aq) + NO3-(aq)
monobasic
Ethanoic acid
CH3COOH(aq) ⇌ H+(aq) + CH3COO-(aq)
monobasic
+
2Sulphuric acid
H2SO4(aq) → 2H (aq) + SO4 (aq)
dibasic
The fizz of drinks
Soft drink tablets contains solid acid (e
...
citric acid, C6H8O7) & sodium bicarbonate
- When tablet is added to water, citric acid ionises and the H+ produced reacts with
sodium bicarbonate to produce carbon dioxide gas, making them fizz
Strong and Weak Acids
Strong Acid - acid that completely ionises in water
...
E
...
H2SO4, HNO3, HCl
H2SO4(aq) → 2H+(aq) + SO42-(aq)
In above H2SO4 has completely been ionized in water, forming 3 kinds of particles:
- H+ ions
- SO42- ions
- H2O molecules
Strong acids react more vigorously with metals than weak acids – hydrogen gas
bubbles are produced rapidly
Weak Acids - acids that partially ionise in water
...
Their reactions are reversible
...
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Comparing Strong and Weak Acids with Concentrated and Dilute Acids
CONCENTRATION
STRENGTH
Is the amount of solute (acids or alkalis) Is how much ions can be disassociated
dissolved in 1 dm3 of a solution
into from acid or alkali
It can be diluted by adding more water
to solution or concentrated by adding The strength cannot be changed
more solute to solution
Comparing 10 mol/dm3 and 0
...
1 mol/dm3 of ethanoic acids
- 10 mol/dm3 of ethanoic acid solution is a concentrated solution of weak acid
- 0
...
1 mol/dm3 of hydrochloric acid solution is a dilute solution of strong acid
Bases and Alkalis
Bases are oxides or hydroxides of metals
Alkalis are bases which are soluble in water
Laboratory Alkalis
- Sodium Hydroxide, NaOH
- Aqueous Ammonia, NH4OH
- Calcium Hydroxide, Ca(OH)2
All alkalis produces hydroxide ions (OH-) when dissolved in water
...
They don’t behave as acids in absence of water
...
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Properties of Alkalis
- Alkalis have a slippery feel
Floor and oven cleaners contain NaOH (strong alkalis)
Ammonia (mild alkalis) is used in liquids to remove dirt and grease from glass
- Alkalis are hazardous
Dilute alkalis are irritants
Concentrated alkalis are corrosive and burn skin (caustic(i
...
burning) alkalis)
Indicators and pH
Indicators are substances that has different colours in acidic and alkaline solutions
Common indicators:
Litmus
Methyl orange
Phenolphtalein
The table shows the change of colours made by some indicators
Indicator
Colour in acids colour changes at pH Colour in alkalis
Phenolphtalein
Colourless
9
Pink
Methyl orange
Red
4
Yellow
Litmus
Red
7
Blue
Screened methyl orange
Red
4
Green
Bromothymol blue
Yellow
7
Blue
The pH Scale
A measure of acidity or alkalinity of a solution is known as pH
pH 7 is neutral – in pure water
solutions of less than pH 7 are acidic
...
The
smaller pH, the more acidic the solution is and more hydrogen ions it contains
...
The solution contains hydroxide ions
...
- Alkalis change the colour of indicators
Alkalis turn common indicator litmus – red litmus to blue
- Alkalis react with acids
The reaction is called neutralisation
- Alkalis react with ammonium compounds
They react with heated solid ammonium compounds to produce ammonia gas
(NH4)2SO4(s) + Ca(OH)2(aq) → CaSO4(aq) + 2NH3(g) + 2H2O(l)
- Alkalis react with solutions of metal ions
Barium sulphate, BaSO4(aq), contains Ba2+(aq) ions
Ca(OH)2(aq) + BaSO4(aq) → Ba(OH)2(s) + CaSO4(aq)
The solid formed is precipitate – the reaction is called precipitate reaction
Strong and Weak Alkalis
Strong Alkalis - base that completely ionises in water to form OH-(aq) ions
...
E
...
NaOH, KOH, Ca(OH)2
Ca(OH)2(s) → Ca2+(aq) + 2OH-(aq)
Weak Alkalis - base that partially ionise in water
...
Their reactions are reversible
...
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Universal indicators
It can be in paper or solution form
...
It gives approximate pH value
...
pH meter
A hand-held pH probe is dipped into solution and meter will show the pH digitally
or by a scale
...
pH sensor and computer
A probe is dipped into solution and will be sent to computer through interface
used to measure pH of solution
...
pH Around Us
- Substances in body involved in good digestion have different pH values
- Blood to heart and lungs contains CO2 making blood slightly acidic
- Acids are used in food preservations (ethanoic acid to preserve vegetables;
benzoic acid used in fruit juices, jams and oyster sauce)
- pH affects plant growth – some plants grow in acidic soil; some need alkaline soil
- When hair is cleaned with shampoo which is alkali to dissolve grease, hair can be
damaged unless it’s rinsed or acid conditioner is used to neutalise excess alkali
Ionic Equations
Ionic equation is equation involving ions in aqueous solution, showing formation
and changes of ions during the reaction
Rule to make ionic equations:
- Only formulae of ions that change is included; ions don’t change = omitted
- Only aqueous solutions are written as ions; liquids, solids and gases written in full
Reaction Between Metals and Acids
For example, reaction of sodium with hydrochloric acid
2Na(s) + 2HCl(aq) → 2NaCl(aq) + H2(g)
Its ionic equation is written as:
2Na(s) + 2H+(aq) + 2Cl-(aq) → 2Na+(aq) + 2Cl-(aq) + H2(g)
Since 2 Cl-(aq) ions don’t change, they’re not involved in reaction
...
So we’re left with:
2Na(s) + 2H+(aq) → 2Na+(aq) + H2(g)
Reaction Between Soluble Ionic Compounds and Acids
e
...
Reaction of sodium hydrogencarbonate with hydrochloric acid
NaHCO3(aq) + HCl(aq) → NaCl(aq) + CO2(g) + H2O (l)
Its ionic equation is:
Na+(aq) + H+(aq) + CO32-(aq) + H+(aq) + Cl-(aq) → Na+(aq) + Cl-(aq) + CO2(g) + H2O(l)
Since Na+(aq) and Cl-(aq) ions don’t change, we omit them, leaving:
H+(aq) + CO32-(aq) + H+(aq) → CO2(g) + H2O(l)
CO32-(aq) + 2H+(aq) → CO2(g) + H2O(l)
Reaction Between Insoluble Ionic Compounds and Acids
e
...
Reaction between iron(II) oxide and sulphuric acid
FeO(s) + H2SO4(aq) → FeSO4(aq) + H2O(g)
Its ionic equation is:
FeO(s) + 2H+(aq) + SO42-(aq) → Fe2+(aq) + SO42-(aq) + H2O(g)
Note: FeO is written in full as it’s solid (although it’s an ionic compound)
Since SO42-(aq) ions don’t change, we omit SO42- ions, leaving:
FeO(s) + 2H+(aq) → Fe2+(aq) + H2O(g)
E
...
Reaction between calcium carbonate and hydrochloric acid
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
Its ionic equation is:
CaCO3(s) + 2H+(aq) + 2Cl-(aq) → Ca2+(aq) + 2Cl-(aq) + CO2(g) + H2O(l)
Since 2 Cl-(aq) ions don’t change, we omit Cl- ions, leaving:
CaCO3(s) + 2H+(aq) → Ca2+(aq) + CO2(g) + H2O(l)
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Reactions Producing Precipitate
E
...
Reaction between calcium hydroxide and barium sulphate
Ca(OH)2(aq) + BaSO4(aq) → Ba(OH)2(s) + CaSO4(aq)
Its ionic equation is written as:
Ca2+(aq) + 2OH-(aq) + Ba2+(aq) + SO42-(aq) → Ba(OH)2(s) + Ca2+(aq) + SO42-(aq)
Since Ca2+(aq) and SO42-(aq) ions don’t change, we omit them, leaving:
Ba2+(aq) + 2OH-(aq) → Ba(OH)2(s)
Displacement Reactions
E
...
Reactions between magnesium with zinc sulphate
Mg(s) + ZnSO4(aq) → MgSO4(aq) + Zn(s)
Its ionic equation is written as:
Mg(s) + Zn2+(aq) + SO42-(aq) → Mg2+(aq) + SO42-(aq) + Zn(s)
Since SO42-(aq) ions don’t change, we omit them, leaving:
Mg(s) + Zn2+(aq) → Mg2+(aq) + Zn(s)
Neutralization is the reaction between acid and base to form salt and water only
...
E
...
NaOH + H2SO4 forms Na2SO4 + H2O
H2SO4(aq) + NaOH(aq) Na2SO4(aq) + H2O(g)
Ionic equation is:
+
H (aq) + OH-(aq)→ H2O(g)
Plants don’t grow well in acidic soil
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3 Preparation of Salts
Soluble and Insoluble Salts
Soluble
Insoluble
All Nitrates
All Supates
BaSO4, CaSO4, PbSO4
All Chlorides
PbCl, AgCl
Potassium, Sodium, Ammonium salts
K2CO3, Na2CO3, NH4CO3
All Carbonates
K2O, Na2O
All Oxides
Preparation of Insoluble Salts
Insoluble salts, e
...
BaSO4, CaSO4, PbSO4, PbCl, AgCl and most carbonates, can be
prepared by reacting compound containing the wanted cation with another
compound containing the wanted anion
...
E
...
Preparation of BaSO4
First BaCl, since it contains wanted barium ion, is reacted with H2SO4, since it
contains wanted sulphate ion, to produce solid BaSO4 & aqueous KCl
...
Salt is washed with water to completely remove KCl & filter paper is squeezed with
another filter paper to dry BaSO4
...
studyguide
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0cm3 acid, as standard solution, is placed in conical flask using pipette
...
Volume of alkali added is measured
...
0cm3 acid again with pipette & add same volume of alkali as before to prevent
excess alkali/acid because both reactant & product are aqueous
...
Only metals like zinc and magnesium, which moderately react with dilute acids, are
used
...
g
...
Then the
mixture is filtered off to separate Zn from ZnSO4
...
The crystals then filtered and squeezed between filter papers to dry
...
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...
By Reacting Carbonate with Acid
E
...
Reacting CaCO3 with Acids
K2CO3(s) + H2SO4(aq) K2SO4(aq) + CO2(g) + H2O(l)
The same process is used as reaction of acid with metal, just that carbon dioxide is
produced
...
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Since the reaction is reversible so H2 and O2, reproduced from decomposition of
produced NH3, are passed over the catalyst again to produce ammonia
...
Higher pressure
2
...
This is because:
- Using low temperature is too slow to reach equilibrium
- Using high pressure involves safety risk and higher cost
Ammonia as Fertilizers
Plants need nitrogen as one of component for growth and ammonium fertilizers
contain Nitrogen for that
...
g
...
Deduce, in terms of nitrogen content, which of these fertilizers best for plants
...
2% of N
= 46
...
When excess fertilizers washed away by rain, nitrate ions in it gets into rivers and
helps aquatic plants like algae to grow swiftly
...
Decay of this organic matter uses up oxygen, hence
killing aquatic animals
...
Nitrate ions from nitrogen in soil leaches down the soil into groundwater due to its
solubility
...
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It’s soluble in water and emits heat when dissolved
...
Sulphur is reacted with oxygen to produce sulphur dioxide, SO2
S(g) + O2(g) → SO2(g)
2
...
If there’s impurities, the catalyst
will be “poisoned” and the reaction will be less effective
...
Sulphur dioxide is further reacted with oxygen to produce sulphur trioxide
...
According to graph:
- Low temperatures yields high percentage of sulphur
trioxide at equilibrium
Dynamic equilibrium is the state when forward and
backward reaction occurs at same speed and the
concentration of reactant and product is equal
...
Although lower temperature is required for high yield, 450oC is instead used in the
process as the reaction will be too slow with low temperatures
...
A catalyst vanadium(V) oxide, V2O5, is used to increase the yield of sulphur
trioxide
...
4
...
SO3 is not reacted with water right now as mist forms at this temperature
...
Oleum is diluted with water to produce sulphuric acid
...
Uses of Sulphur Dioxide
Sulphur dioxide is a colourless, toxic gas with suffocating smell, denser than the air
and dissolves in water
...
It is used:
- In sulfite manufacturing used in digestion & bleaching wood pulp to make paper
- As food preservatives such as dried fruit and fruit juices
...
studyguide
...
The Modern Periodic Table
Differences to Mendeleev’s:
- 115 elements while for Mendeleev’s is 69
...
Period – horizontal row of elements in periodic table
Group – vertical column of elements in periodic table numbered from I to 0
Elements between Group II and Group III – transition metals
8
...
e
...
Group II has elements with valency of 2 electrons
...
- Elements on left side periodic table lose ions to form cation
...
- Elements in Group IV can lose or gain electrons depending on reacting
element
...
e
...
Sodium in Group I forms NaCl, so other elements in Group I does the same
...
5) Changes in Group
- Proton number increase going down the group
- On each sides of periodic table, the change of the proton number small & gradual
- In transition metals, the gradual change is larger
Using the Periodic Table
Predicting Properties
1) Formula and Structures
Given chlorine, iodine and bromine of Group VII forms molecules of Cl2, I2 and
Br2 respectively, predict the molecular formula of Fluorine
...
2) Properties of Elements
Properties of element changes down the group
...
e
...
Element
Proton Number Melting Point (oC) Boiling Point (oC)
Fluorine
9
-220
-118
Chlorine
17
-101
-35
Bromine
35
-7
59
Iodine
53
114
184
Astatine
85
> 114
> 184
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...
The solutions
turn red litmus paper blue
...
These increases down the group
- reacts easily in air
...
They have similar formulae
- they become more reactive down the group
Name
Symbol
Density (g/cm3)
Melting point
(oC)
Lithium
Li
0
...
97
98
Potassium
K
0
...
5
39
Caesium
Cs
1
...
1: The physical properties and formulae of Group I metals
Group VII Elements – The Halogens
These are elements which reacts with most metals to form salts
- very reactive elements
- have seven outer shell electrons
- each molecule in the element is diatomic (contains two atoms, eg F2)
- elements become darker and solidify down the group
- they have low melting and boiling points which increases down the group
- all halogens are poisonous
Element
Fluorine
Chlorine
Bromine
Iodine
Molecular
formula
F2
Cl2
Br2
I2
Melting
Boiling
point (oC) point (oC)
-220
-189
-101
-35
-7
59
114
184
State at
r
...
p
...
State the chemical
equation of the reaction
...
They do not form bonds
- have stable electronic configuration with full electrons on their shells
- coloured gases consisting of single atoms (monoatomic)
- low melting and boiling points
Uses of the Noble Gases
- argon used in light bulbs as it wouldn’t react with the hot filament
- neon used in neon advertising strip lights
- helium used in small and weather balloons, and airships for less density
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8
...
g
...
g
...
g
...
g
...
g
...
END OF CHAPTER 8
CHAPTER 9 –METALS
9
...
Pure metals are weak as the layers of atoms slide over each other easily
...
Uses of Alloy:
- Steel (mixture of iron, little carbon and trace elements)
- Brass (copper and zinc) – tough and corrosive-resistant
- Coin metals (copper with other metals e
...
nickel) – tough, resistant and
stand up to wear
Uses of Stainless Steel
is an alloy of iron containing chromium or nickel
...
studyguide
...
2 Reactivity Series
Reaction of Metals with Water
Pottasium, Sodium, and Calcium reacts with cold water to form:
M(s) + 2H2O(l)
MOH(aq)
+ H2(g)
Metal + Water Metal Hydroxide + Hydrogen
Magnesium, Zinc, Iron reacts with steam to form:
M(s) + 2H2O(g)
MO(s) + H2(g)
Metal + Water Metal Oxide + Hydrogen
Iron does not react with water
Copper and Gold have no reaction with water and steam
Reaction of Metals with Dilute Hydrochloric Acid
Pottasium, Sodium, Calcium, Magnesium, Zinc and Iron reacts with dilute
hydrochloric acid to form:
M(s) + 2HCl(aq) MCl2(aq) + H2(g)
Metal + Acid Metal Chloride + Hydrogen
Lead reacts with warm hydrochloric acid slowly
Copper and Gold have no reaction with dilute hydrochloric acid
Displacement Reactions
Displacement reaction is the displacement of ions of metal from compounds of
metals lower in reactivity series by metals higher in reactivity series
...
g
...
Mg(s) → Mg2+(aq) + 2eCu2+(aq) + 2e- → Cu(s)
Loss of electrons is due to it’s less reactive as less reactive metal has higher chance
of losing electrons
...
Mg(s) + KCl2(aq) No reaction
E
...
Displacement from metal oxides
Metal higher in reactivity series displaces oxides of metals lower in reactivity series
...
Ca(s) + Ag2O(s) CaO(s) + 2Ag(s)
This is called thermit reaction large amount of heat is produced
...
At higher position, stronger heat is needed
...
g
...
Reaction of Metal Oxides with Hydrogen
The lower position of metal in reactivity series, the easier hydrogen remove oxygen
from metal oxide by heating
...
E
...
PbO reacts with H2 can be reduced by bunsen burner flame temperature
PbO(s) + H2(g) Pb(s) + H2O(l)
Decomposition of Metal Carbonates
The lower position of metal in reactivity series, the easier hydrogen remove oxygen
from metal oxide by heating
...
E
...
CuCO3 reacts decomposes by heat of bunsen burner flame temperature
CuCO3(s) Cu(s) + CO2(g)
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...
- The ores contain useful and unwanted materials
...
- Metal is extracted from the mineral
...
Most Reactive – hardest to extract – strong bonds in compounds; by electrolysis –
decomposing compounds with electricity
...
Physical properties (e
...
melting point, strength, density, conductivity)
2
...
g
...
Cost
The Uses of Some Metals and Their Reasons
Metal
Uses
Reason for the choice
- Drink cans
- Low density, non-toxic, cheap
Aluminium
- Window frames
- Resists corrosion, strong
- Electrical wires
- Ductile, good conductor of electricity
Copper
- Water pipes
- Strong, malleable, resists corrosion
- Jewellery
- Shiny and attractive, very malleable
Gold
- Protective coating - Good reflector of heat and light
- Supersonic aircraft
Titanium
- Light but strong, resists corrosion
- Spacecraft
Recycling of Metals
How Much is Left?
There are many iron on the surface but copper and tin are seriously reducing
...
studyguide
...
g
...
E
...
separat metals in alloys is hard
- Transport costs for collecting scrap metal is high, e
...
trucks should be used
- People are not interested in depositing their used materials in recycling bins
9
...
E
...
used computer parts processed to extract gold used for electrical contacts of
processors and memory chips
- Recycling saves the cost of extracting new metals
- Recycling benefits environment, e
...
if there is a car wasteland, it causes eyesore
The Blast Furnace
1
...
Carbon dioxide produced in 1 reacts with more coke to produce carbon monoxide
Problems with Recycling
- Metals are recycle if the cost is cheaper than extraction
...
g
...
The carbon monoxide reacts with iron(III) oxide to produce molten iron, which runs
down to the bottom of the furnace
4
...
studyguide
...
Iron ore contains many impurities (silicon, sulphur, phosphorus, etc
...
Slag runs down to the
bottom of the furnace, floating on top of molten iron
6
...
Slag is for road construction
...
Referring to equation, not all iron(III) oxide reacted with carbon, only small amount
Fe2O3(s) + 3C(s) → 2Fe(l) + 3CO3 (g)
Rusting
Rusting – corrosion of iron and steel
Rust – brown solid product formed during rusting
Rust is hydrated iron(III) oxide Fe2O3 xH2O where water molecules varies
...
Advantages of steel:
- it is strong and tough
- it can be bent and stretched without shattering
Tubes
A
B
C
After a few days, only nail in tube A rust
...
In boiled water, the nail doesn’t rust in B as boiled water removes
dissolved air while in C, CaCl keeps air dry so there’s no water
...
They are then combined with CaO and removed as slag
...
Preventing Rusting
- Surface protection
- Sacrificial protection
- Use of stainless steel
Different Types of Steel:
- Mild steel – is a low carbon steel with 0
...
It is used for car bodies, ships, railway lines and
steel rods to reinforce concrete
- Hard steel – is a high-carbon steel with about 1% carbon
It is harder than mild steel and less malleable
...
It is used to make cutleries, medical
instrument and pipes in chemical industries
...
g
...
studyguide
...
g
...
If layer is broken, water & air
reach underneath layer, overlying metal still protect it
...
2) Protecting ships – blocks of zinc are attached to hulls to corrode instead of
steel which is the ship metal
...
Magnesium corrodes first than steel
...
1 Air
The atmosphere is a layer of air containing mixture of
several gases
...
The composition of water vapour varies
from 0-5%, depending on the humidity of air
...
Hence, to find the volume of oxygen in air collected in syringe:
Volume of O2 = Initial volume of air – Final volume of air
For instance, the initial volume of air in one syringe is 80cm3 and the final volume is
64cm3
...
Then, the air is cooled to -25oC
to freeze water vapour to be removed and the remaining air is cooled and
compressed to become liquid which is then separated into its singular constituents
by fractional distillation as each constituent has different boiling point
...
studyguide
...
If flames are produced during combustion, it’s called burning
...
When adequate supply of oxygen is available during burning, it will create a
complete combustion
...
E
...
CH4(g) + 2O2(g) CO2(g) + 2H2O(g), makes up a complete combustion
A Test for Combustion
When air hole is closed, air cannot enter
supplying oxygen, and hence soot (unburnt
carbon) and CO is produced from incomplete
hydrocarbon gas combustion
...
When air hole is
opened, air supplies plenty of oxygen, allowing
complete combustion
...
From nature, pollutant sources are volcanoes, forest fires, decay of dead matter,
etc
...
The main air pollutants are:
1
...
Cells then die
...
Sulphur dioxide
Where it comes from?
Combustion of fossil fuels containing sulphur impurities; volcanic eruptions
What hazard it brings?
Lung irritant, eye irritant, acid rain
How to prevent this?
- Prevent using fuels containing sulphur impurities, e
...
coal
- Reduce the sulphur impurities inside fossil fuels
- Spray exhaust gases from factories with water/hydrated CaO/alkalis to absorb
sulphur dioxide before it’s released into the atmosphere
- Add CaO to soil and rivers to neutralize acid rain
3
...
)
Where it comes from?
Lightning activity; forest fires; internal combustion engines (as nitrogen oxides
are formed by oxygen and nitrogen under high temperature); power stations
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What hazard it brings?
Eutrophication, lung damage, acid rain
How to prevent this?
- Install catalytic converters in cars
- Design car engines which run at lower temperatures
Chemistry around us: ACID RAIN
Acid rain is formed by 2 main constituents – SO2 and NO2
Sulphur dioxide/nitrogen dioxide, both react with oxygen and water to form
sulphuric acid/nitric acid
...
2SO2(g) + O2(g) + H2O(l) 2H2SO4(aq)
4NO2(g) + O2(g) + 2H2O(l) 4HNO3(aq)
Effects of Acid Rain
- The acid corrodes buildings, CaCO3 materials and metal statues
...
The product is CO2,
which is non-polluting gas, and calcium sulphite
...
2H2O(g)
4
...
Unburnt hydrocarbons
Where it comes from?
Internal combustion engunes; incomplete combustion of hydrocarbons
What hazard it brings?
Carcinogenic, forms photochemical smog
How to prevent this?
- Install catalytic converters in cars
- Reduce number of cars on road
- Create efficient engines in cars to ensure complete hydrocarbon combustion
6
...
It’s created by reaction of
nitrogen oxides with volatile organic compounds in presence of UV radiation
...
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- It corrodes and kills plants and trees
How to prevent this?
- Don’t use CFCs/replace it with HCFCs which destroys faster
...
It is produced by reaction between
NO2 and O2 in the oresence of sunlight to form NO, O and O2
...
NO2(g) + 2O2(g) NO(g) + O + O2(g)
The oxygen atom is reacted with the oxygen molecules formed to form ozone, O3
...
Chemistry around us: DESTRUCTION OF OZONE LAYER
How is it depleted?
Ozone layer absorbs some UV radiation and reflects some back to space
...
In the presence of light, CFC
decompose into Cl2 at the stratosphere where ozone is located
...
Cl + O3(g) ClO(g) + O2(g)
The reaction uses up ozone which covers the earth and hence creating a hole in the
layer
...
Tackling Depletion of ozone layer:
- Don’t use CFCs/replace it with HCFCs which destroys faster
...
However, increased industrialization releases more greenhouse gases to
atmosphere, contributing to Global Warming (increase in temperature of Earth’s
atmosphere due to trapping of heat by greenhouse gases)
...
EXAMPLES OF GREENHOUSE GASES ARE:
1
...
2
...
3
...
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TACKLING GLOBAL WARMING
- Reduce the use of fossil fuels
- Use alternative forms of energy such as wind, tidal and hydroelectric power
- Use more electric vehicles
- Reduce number of cars on road
- Create efficient engines in cars to ensure complete hydrocarbon combustion
Chemistry around us: CARBON CYCLE
0
...
Carbon cycle is the removal of carbon dioxide by plants by
photosynthesis and the replacement of these carbon molecules by combustion,
respiration and natural processes
...
Man upset this balance
...
Some carbon is used up in plants for growth and
development, while some others are released to atmosphere during respiration
...
Animals:
When herbivores and omnivores eat plants, they gain carbon from them to grow
and develop
...
When animals
respire, they release carbon dioxide
...
WHAT NON-LIVING THINGS DID
Carbon monoxide and carbon dioxide are released from electric power plants,
exhaust fumes and factory emissions
...
This makes man
depleting natural resource as they use them rapidly than the time needed to
reform, damages natural environment and upsetting balance of carbon cycle
...
2NO(g) + CO(g) N2(g) + 2CO2(g)
In second half of converter, unburnt hydrocarbons (e
...
octane, C8H18) reacts with
more air to form CO2 and H2O
...
These reactions are all redox
...
studyguide
...
Lead compounds
Where it comes from?
- Combustion of leaded petrol in car engines
What hazard it brings?
- Causes lead poisoning which leads to brain damage
...
2 Water
Water is most available liquid on Earth covering 70% of the planet surface
...
Inside that Water
Naturally Occuring Substances
- Mineral salts – aluminium, calcium, potassium, etc
...
from waste discharge
- Phosphates from fertilizers, detergents or sewage treatment plants
- Nitrates from fertilizers or sewage treatment plants
- Sewage from sewage treatment plants or septic systems
- Harmful microbes from sewage treatment plants, septic systems, naturally
occuring in water or growing in abundance due to pollution
- Acid from industrial discharges
- Oil spills from oil tankers
Important or Silent Killer?
Beneficial Stuff
Mineral salts
- Needed for basic functions of human body such as bone growth, fluid regulation,
normalize nerve and muscle functionality, metabolism control, growth, etc
...
Dissolved oxygen
- Needed for respiration and growth of aquatic life
...
Organic matter
- Needed for growth of aquatic organisms
Harmful Stuff
Acid
- Kills aquatic organisms and plants
- Makes water acidic and corrosive – unsafe to drink
Nitrates
- Causes eutrophication which deprives marine organisms of oxygen
- Nitrate ions may cause breathlessness or kill babies when consumed
Phosphates
- Can cause eutrophication as it encourages the growth of algae, hence killing
aquatic organisms when they die and takes away oxygen
Heavy metal ions
- These are carcinogenics that can cause skin cancer, liver cancer, lung cancer, etc
...
Oil
- Traps bird’s feathers and kills them eventually
- Depletes oxygen as air cannot mix with water to provide sufficient oxygen
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Tackling Water Pollution
- Proper disposal of rubbish to prevent more water pollution
- Prohibit activities potentially causing water pollution near rivers/reservoirs such
as camping or swimming
...
Water from rain and river downstream is collected in reservoir
...
Water is transported via pipe to a flocculation tank where alum, Al2(SO4)3, and
lime, Ca(OH)2 are added to water so that small solid clay particles join together
into large lumps of solid (coagulation)
...
Water is moved to sedimentation tank where the lumps of solid settles to the
bottom of the tank
...
Carbon, in form of activated
charcoal, is added to remove the taste and smell of water
...
Water is filtered off in filtration tank, where there are sand particles filter which
traps the remaining solid particles in water
...
Chlorine and fluorine are added in chlorination tank
...
Chlorine is used to kill bacteria while fluorine is used to strengthen teeth
...
Salts in seawater must be removed so it’s drinkable
...
END OF CHAPTER 10
Functional Groups
- Is the special group of atoms available in homologous series compunds which
responsibles for the chemical properties of the compound
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All compounds in homologous series have functional group except alkanes
...
Fractional
distillation uses this property to separate the hydrocarbons in crude oil
...
Then the formula of
propane is C3H8
- Ends with suffix –ane
- Next alkane formula differ by –CH2 atoms
...
When naphtha is treated, not only it
becomes a better fuel, it also contain more aromatic hydrocarbons, alkene and
cyclic hydrocarbons which are important for petrochemical industry
...
As
oil reserves deplete, competition between 2 main uses of oil will be more intense
...
Eg: methane
All alkanes are saturated
...
They
only have single bond (–) only
...
g
...
This is usually indicated by double bond (=) or triple bond () with another
carbon atoms
...
1 Alkanes
- Usually in fuels, examples: natural gas, petrol, diesel
- Are homologous series
- Have a formula of CnH2n+2
From the table,
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- Melting points and boiling points increase as the bonds become larger and
heavier which increases the forces of attraction between molecules so more
energy (from heat) is needed to separate them with the increase of strength of
forces of attraction
Substitution reaction – the reaction in which one or more atoms replace other
atoms in a molecule
Light is needed to break covalent bond between chlorine moleculeatoms
- Alkanes are insoluble in water but soluble in organic solvents such as
tetrachloromethane as alkanes are organic compounds
- Alkane density increases down the series; all alkenes are less than 1g/cm3
- Alkanes become more viscous (uneasily flow) going down the series as the longer
molecules tangles together when it flows
- Alkanes become less flammable down the series as B
...
becomes larger
- Alkanes are unreactive with either metals, water, acids or bases because the C – C
and C – H covalent bonds are harder to break
Reaction of Alkanes
Have same chemical properties – they don’t react with most chemicals
Combustion
Alkanes burn in air to ALWAYS form carbon dioxide and water
...
Example: Butane is commonly used camping gas
...
2 C4H10(g) + 13 O2(g) 8 CO2(g) +10 H2O (l)
11
...
- all alkene names end with –ene
...
- have similar properties like alkane going down the series
...
of
Molecular
C
Name
Structural formula
formula
atoms
Condensed
structural
formula
2
ethene
C2H4
CH2 = CH2
3
propene
C3H6
CH3CH2 = CH2
4
butene
C4H8
CH3CH2CH = CH2
Table 25
...
of 4 other atoms
High alkanes burn less completely and gives soot (unburnt carbon) and CO
Reaction with Chlorine/Other Halogens (Alkyl Halides)
Chlorine molecule replaces alkane hydrogen atom with chlorine atom
The Importance of Ethene
Ethanol – solvent & fuel
Ethanoic acid – vinegar
Poly(ethene) – PE plastic variations
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Reactions of Alkenes
Combustion
Burns in air to form carbon dioxide and water
Example: Ethene burns in air
...
It’s produced more than alkane
- Addition of water
Alkene reacts with water, in the form of steam, to produce alcohol
...
H2O
molecule adds to C = C bonds to form alcohol
...
Must use
nickel as catalyst and heat
...
- Addition of bromine
Bromine adds to C = C double bond of alkane molecules
...
Eg: ethene to 1,2 – dibromoethene
C2H4(g)
+
Br2(g)
C2H4Br2(l)
+
Br – Br
Nomenclature
(n) + (bromo) + (alkene name), where n is the number of bromine atoms
...
g
...
Hence we call the product DIBROMOETHENE
...
g
...
Reddish-brown
colour of bromine disappears
...
Characteristics of a Homologous Series
- All members of homologous series have same general formula
- Formula of each member differs by –CH2 group
- Physical properties changes gradually in the increase of carbon atoms
- The members have similar chemical properties
Foods and Unsaturated Compounds
The Manufacture of Margarine
Polyunsaturated food – food containing C=C bond in their molecules
Eg: Vegetable oil
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To produce margarine:
Isomers
Hey, I’m
C6H14!
No, you poser!
I’M C6H14!
Look at the figure above and count the number of carbon and hydrogen atoms in
each case
...
We can’t deny that they have the
same molecular formula
...
Therefore:
Hydrogen is reacted with vegetable oil with presence of nickel catalyst and heat,
which adds to C=C bond, increasing the molecular mass of the compound
- With increase in mass, the compound has higher boiling point
...
- Since only some C=C bonds react with hydrogen, margarine is partially
hydrogenated and each has different hardness, depending on the number of C=C
bonds
...
We crack alkane by catalytic cracking, which is, using catalyst to break alkane into
simpler hydrocarbons
...
The
total number of carbon and hydrogen atoms from products should equal to the
total number of carbon and hydrogen atoms in cracked alkane
...
g
...
Suggest the possible identity of product x
...
Due to different chain length, they have different physical properties (e
...
boiling point)
...
We therefore can’t just say that C6H14 is simply hexane because there are more
variations of C6H14 and each variation has its own name
...
e
...
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- Note that the second number is 3 while in fact, the position closest to the end of
isomer is 2
...
In this case, we put the number as the POSITION THE
SECOND NEAREST TO THE END OF THE ISOMER, that is, 3
...
This is so not useful
...
- Note that the first number 2 indicates the position of methyl group (CH3)
attached to a carbon atom from the nearest end
...
Since 2 is closer, we put 2 in place
...
Since it’s attached
to the same carbon atom as the first methyl group, we put the same number 2
...
This comes from the number of carbon
atoms in the STRAIGHT chain only
...
- Bear in mind that “di” in “dimethyl” indicates the number of methyl groups in the
isomer (“di” means two)
...
Figure 12(b)(ii) is another variation of the isomer 2,2-dimethylbutane
- Students often misinterpret this as 1,2,2-trimethylpropane while in fact, we don’t
take the last bend in the chain as another methyl group
...
Figure 12(c)(i) and Figure 12(b)(ii) is another isomer called 2,3-dimethylbutane
- See that we can flip the positions of methyl group without changing formula
For isomerism in alkene in Figure 13(c), we apply the same theory as isomerism in
alkane, and just to only add a double bond indication
...
In Figure 13(a), it’s hept-1-ene,
can be called heptene, can be changed to hept-2-ene in Figure 13(b), where the
number in between indicates position of double bond from nearest isomer end
...
studyguide
...
3 Alcohols
Are homologous series with general formula CnH2n+1OH
- They have –OH functional group (hydroxyl group)
- All alcohols end with suffix -ol
First three members of the series (so that you’d have idea on the next)
Methanol, CH3OH
Ethanol, C2H5OH or CH3CH2OH
Propanol, C3H7OH or CH3CH2CH2OH
For alcohol, the –OH is not of hydroxide ion, OH-, but is covalent bond between
oxygen and hydrogen, O – H
Making Ethanol
- Fermentation of sugars with yeast
- Reacting ethene with steam
Fermenting glucose
Fermentation is breakdown of sugars into smaller molecules by microorganisms
...
Oxygen is removed by limewater and carbon dioxide is produced
during fermentation
...
Reacting Ethene with Steam
Ethene and steam are passed over phosphoric acid H3PO4 (as a catalyst) under high
temperature of 300oC and pressure of 65 atm
...
The ethanol is separated by fractional distillation
...
E
...
combustion of ethanol
C2H5OH(aq) + 3O2(g) 2CO2(g) + 3H2O(l)
Oxidation
1
...
g
...
The product is carboxylic acid and water
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g
...
Alcohol can be oxidized when left in air with bacterial enzymes as catalyst
...
E
...
ethanol produces water and ethanoic acid when left in air
...
4
11
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studyguide
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From natural gas
Natural gas is passed over air and catalyst to form ethanoic acid and water
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g
...
Oxidation (explained in Chapter 11
...
For instance, example above is butyl
propanoate, where “butyl” is from butanol; “propanoate” is from propanoic acid
...
g
...
5 Synthetic Macromolecules
Macromolecule is a large molecule made by joining together many small molecules
Polymer is a long-chain macromolecule made by joining together many monomers
Polymerisation is the addition of monomers to make one large polymer
- Carboxylic acids react with bases to form salt and water (neutralization)
E
...
Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and
water
...
E
...
Ethanoic acid reacts with sodium carbonate to form sodium ethanoate and
water
...
Sulfuric acid is added as catalyst then heat mixture
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The reaction is reversible
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This is HYDROLYSIS
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From monomer to polymer
Example: Formation of poly(ethene) from ethene
Ethene has double bond
...
Repeat unit is the simplest part of the polymer which is repeated many times to
form the polymer
...
From this repeat unit, to find the monomer
formula, we add double bond between C – C and remove the bonds on each of
their sides
...
studyguide
...
Therefore we can
also call nylon as polyamide
...
Nylon
Dicarboxylic acid and diamine undergo condensation polymerisation to form nylon
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studyguide
...
6 Natural Macromolecules
CARBOHYDRATES
Carbohydrates contain carbon, hydrogen & oxygen
...
The simplest carbohydrate is C6H12O6 (glucose)
...
The overall reaction is:
nC6H12O6 (C5H10O5)n + nH2O
The linkage between the monomers in terylene is called ester linkage
...
Starch can also be broken down into glucose by heating with sulfuric acid
...
Today, we use terylene in fabrics as it’s strong, resists stretching and sinking and
doesn’t crumple when washed
...
Only that their monomers are only
amino acids joined together
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PROBLEMS ASSOCIATED WITH PLASTICS
- Plastics are non-biodegradable – they cannot be decomposed by bacteria
...
- Plastics produce carbon dioxide when burnt – increases global warming
...
Proteins can be called as polyamide as it has amide linkage
...
This adds
water molecule into the polymer
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studyguide
...
Only that their
monomers consists of glycerol and fatty acids; different from terylene
...
This is HYDROLYSIS
...
GOOD LUCK IN YOUR EXAMINATIONS!
Copyrights AF/PS/2009/2010
www
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Copyrights AF/PS/2009/2010
www
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pk
67
*Periodic table and qualitative analysis notes are reproduced with permission from Cambridge
International Examination Syndicate which itself is a subordinate of University of Cambridge
...