Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Chapter 1
Chemistry 9th Notes By F
...
Khan
Chapter 1
FUNDAMENTALS OF CHEMISTRY
Science
The word Science is derived from the Latin word scientia, which means knowledge
...
It is the knowledge that provides understanding of this world
and how it works
...
Chemistry
Chemistry is the branch of science that deals with the study of properties, composition and structure of matter
along with chemical changes involved in it and principles that govern these changes
...
There are four states of matter:1
...
Solid
Gas
2
...
Liquid
Plasma
Importance of chemistry in our daily life
1
...
2
...
3
...
4
...
5
...
For example it
has generated toxic wastes, contaminated water and polluted air around us
...
Plato adopted Empedocles theory and coined the term element to
describe these substances
...
He thought
that all matter was derived from four elements:
Earth:
Air:
Fire:
Water:
Earth is dry and cold
Air is wet and hot
Fire is hot and dry
Water is cold and wet
Contact: ssva015@gmail
...
A
...
According to this theory matter is
made up of small indivisible particles called atoms
...
Main postulates of his theory are as follows:
1
...
3
...
All elements are composed of tiny indivisible particles called atoms
...
They have same mass and same volume
...
They combine in simple ratios
...
Modern picture of an atom
Modern research has clearly shown that atom is further composed of subatomic particles such as electron,
proton and neutron
...
What do you know about the corpuscular nature of matter?
Ans
...
Empedocles concept:
An ancient Greek philosopher, Empedocles thought that all materials are made up of four things called
elements
...
e
...
Aristotle concept:
Aristotle also adopted the concept of four elements
...
This concept of four elements existed for more than two thousand years
...
Physical Chemistry
The branch of Chemistry that deals with the laws and theories to understand the structure and changes
of matter is called Physical Chemistry
...
Organic Chemistry
The branch of Chemistry that deals with substances containing carbon is called Organic Chemistry
...
3
...
4
...
) that occur in living organisms is called Biochemistry
...
Industrial Chemistry
The branch of chemistry that deals with the methods and use of technology in the large scale production
of useful substances is called industrial chemistry
...
com
Page 2
Chapter 1
Chemistry 9th Notes By F
...
Khan
6
...
7
...
8
...
Differentiation between branches of Chemistry
Acetic acid chemical formula: CH3COOH
Source: Vinegar which contain 5% acetic acid
...
Let’s see how various types of studies on this compound can help us to differentiate between the above
mentioned eight branches of chemistry
...
Explanation of conversion of acetic acid from solid to liquid and liquid to gaseous state and vice versa,
the application of laws and theories to understand its structure is physical chemistry
...
Since acetic acid is a carbon compound, the study of its methods of preparation and study of its physical
and chemical properties is a part of organic chemistry
...
The component elements of acetic acid are carbon, hydrogen and oxygen
...
4
...
5
...
6
...
7
...
8
...
Contact: ssva015@gmail
...
A
...
1: Identifying examples of different branches of chemistry
SELF ASSESSMENT EXERCISE 1
...
Hair contains a special class of proteins called keratins, which are present in nails and wool
...
ii
...
Hydrocarbons are
compounds of carbon and hydrogen
...
iii
...
Ans: Industrial Chemistry, since extraction of compounds and large scale production of any substance is the
subject of Industrial chemistry
...
Sulphuric acid (H2SO4) is extremely corrosive to skin
...
v
...
Ans: Physical Chemistry, since compression of gases is the matter of physical chemistry
...
com
Page 4
Chapter 1
Chemistry 9th Notes By F
...
Khan
vi
...
Ans: Biochemistry, since compounds that are related to living organisms is studied in biochemistry
...
Element radium decays by emitting a-particles and is converted into another element radon
...
viii
...
Ans: Analytical Chemistry, since it deals with the methods and instruments for determining the composition
of matter
...
The following figure shows simple classification of matter into
different forms:-
Classification of Matter
Substance
Any matter that has a particular set of characteristics that differ from the characteristics of another kind of
matter is called a substance
...
Element
A substance that cannot be converted to other simpler substances is called an element
...
An element is now defined as a substance
whose all the atoms have the same atomic number
...
The properties of compounds are different from the properties of the
elements from which they are formed
...
Elements and compounds have uniform composition throughout
...
com
Page 5
Chapter 1
Chemistry 9th Notes By F
...
Khan
Mixture
An impure substance that contains two or more pure substances that retain their individual chemical
characteristics is called a mixture
...
Examples of mixture are air, water containing dissolved oxygen, table salt dissolved in water, salt +
sand etc
...
For
example sand + salt, oil floating on water etc
...
For example sugar mixed in water, salt
dissolved in water
...
Difference between a Compound and Mixture
Sr
...
They are made up of two or more elements
combined chemically
...
Compounds have fixed properties
...
A compound can have properties different
from its constituents, as a new substance is
formed when the constituents are
chemically combined
...
Mixtures
Mixtures are impure substances
...
The constituents of a mixture are present in
varying ratios
...
Their
properties depend on the nature of their components and the ratios in which they are combined
...
The
properties of a mixture are the same as the
properties of its constituents
...
Atomic Number
The number of protons in the nucleus of an atom is known as its atomic number
...
For e
...
, there is only one proton in the nucleus of hydrogen atom; therefore its atomic number is 1
...
Do you think atomic number of He is 2?
Ans
...
Mass Number
The total number of protons and neutrons in an atom is known as its mass number
...
Q3
...
Carbon atom has 6 protons and 6 neutrons; hence its mass number is 12
No
...
com
Page 6
Chapter 1
Chemistry 9th Notes By F
...
Khan
Example 1
...
How many protons and neutrons are in the
nucleus of an atom of this element?
Solution
Number of protons = atomic number
= 17
Number of neutrons = mass number – atomic number
= 35 – 17 = 18
Relative Atomic Mass and Atomic Mass Unit
An atom is extremely small particle; therefore we cannot determine the mass of a single atom
...
The light isotope
of carbon (C-12) has been chosen as a standard, with reference to which atomic masses of all other elements
can be determined
Thus
“The mass of an atom of an element relative to the mass of an atom of C-12 is called its relative atomic mass”
...
40% as massive as the standard C-12
...
008 amu
Table 1
...
008 amu
14
...
9994 amu
22
...
9815 amu
32
...
453 amu
55
...
Mass of one C-12 atom = 12 amu
1amu =
Contact: ssva015@gmail
...
A
...
A chemical formula tells us:
Which elements are present in a compound
The whole number ratio of their atoms
In a chemical formula element’s symbol and numerical subscripts show the type and the number of each atom
in a compound
...
For example in compound hydrogen peroxide (H2O2) there is one H atom for every O
atom
...
So the empirical formula of hydrogen peroxide is
written as HO
...
The simplest ratio between C, H and O atoms in glucose is 1 : 2 :1
...
Empirical formula of glucose = CH2O
Molecular Formula
A molecular formula gives the actual whole number ratio of atoms of each element present in a compound
...
g
...
Therefore, actual
ratio of hydrogen to oxygen atoms is 2 : 2
...
Q5
...
What is the molecular
formula of glucose?
Ans
...
Difference between Empirical formula and molecular formula
An empirical formula shows the simplest number of atoms of each element in a compound whereas the
molecular formula shows the actual number of atoms of each element in the molecule of a compound
...
Benzene is a compound of carbon and hydrogen
...
There are
actually six C atoms and six H atoms in each molecule of benzene
...
Empirical formula = CH
Molecular formula = C6H6
Q7
...
What are empirical
formulas for these compounds?
Ans
...
com
Page 8
Chapter 1
Chemistry 9th Notes By F
...
Khan
Q8
...
We know that molecular formula of a compound may be same as its empirical formula e
...
H2O, CO2,
HCl, CH4, CCI4, NH4, HBr, PCl3, H2S04 etc
...
For example, molecular formula of benzene is C6H6 which is derived from the empirical formula CH where
the value of n is 6
...
The Empirical Formulae of Some of the Compounds
No
...
2
Write the empirical formulas for the compound containing carbon to hydrogen in the following ratios:
(a) 1 : 4
(b) 2 : 6
(c) 2 : 2
(d) 6 : 6
Answer: (a) CH4
(b) CH3
(c) CH
(d) CH
Q9
...
For e
...
, water (H 2O), carbon
dioxide (CO2), ammonia (NH3), methane (CH4), sulphur dioxide (SO2) etc
...
The molecules of these compounds contain atoms in their simplest ratios
...
3
1
...
There are nine carbon atoms, eight hydrogen atoms and four oxygen
atoms, in this compound
...
Answer: The empirical and molecular formula of aspirin is same i
...
, C9H8O4
...
Vinegar is 5% acetic acid
...
Write its
empirical and molecular formulas
...
com
Page 9
Chapter 1
Chemistry 9th Notes By F
...
Khan
3
...
Write the empirical formula for caffeine
...
Molecular mass of molecule AxB = x (atomic mass of A) + atomic mass of B
For example;
Molecular mass of water H2O = 2(atomic mass of H) + atomic mass of O
= 2(1) + 16
= 2 + 16
= 18 amu
Example 1
...
Determine the molecular mass of glucose C6H12O6 which is known as blood sugar
...
Determine the molecular mass of naphthalene C10H8, which is used in mothballs
...
Ionic compounds consist of oppositely charged ions rather
than separate molecules
...
“The sum of the atomic masses of all the atoms in the formula unit of a substance is called formula mass”
...
5
= 58
...
For example, the
common salt consists of Na+ and Cl- ions
...
So formula unit for common salt is
NaCl
...
com
Page 10
Chapter 1
Chemistry 9th Notes By F
...
Khan
Example 1
...
Sodium Chloride, also called table salt is used to flavor food, preserve meat, and in the preparation of large
number of compounds
...
Solution
Formula mass of NaCl = 1 (atomic mass of Na) + 1 (atomic mass of Cl)
= 1 x 23 + 1 x 35
...
5 amu
2
...
Determine its formula mass
...
4
1
...
Calculate its formula
mass
...
5 + 3 x 16
= 39 + 35
...
5 amu
2
...
Determine the formula masses of baking soda and carbon dioxide
...
Following compounds are used as fertilizers
...
(i) Urea, (NH2)2CO
(ii) Ammonium nitrate, NH4NO3
Solution
Formula mass of urea = 2 [ 14 + 2(1) ] + 12 + 16
= 2(14) + 4(1) + 12 + 16
= 28 + 4 + 12 + 16
= 60 amu
Formula mass of ammonium nitrate = 14 + 4(1) + 14 + 3(16)
= 14 + 4 + 14 +48
= 80 amu
Contact: ssva015@gmail
...
A
...
These species are atoms, ions, free radicals, molecules and formula
units
...
It is electrically neutral
...
There are two types of ions:
1) Cations
An atom or group of atoms having positive charge on it is called cation
...
For e
...
, Na form Na+ by losing one electron, Ca forms Ca+2 by losing
two electrons
...
Non-metal atoms usually gain
one or more electrons and form anions
...
g
...
Q10
...
An ion acquires a net positive or negative charge due to difference in number of protons and
electrons in it
...
Note that sodium has a nucleus of 11 protons and 12 neutrons
...
Around the nucleus, in the ion are 10 electrons, with a total charge of -10
...
5
Explain why?
1
...
Answer: An oxide ion has a nucleus of 8 protons and 8 neutrons
...
8 protons has charge = +8
10 electrons has charge = -10
So, Net charge on the ion =(+8) + ( – 10) = -2
Contact: ssva015@gmail
...
A
...
Magnesium ion, Mg+2 has +2 charge
...
Around the nucleus, there are 10
electrons in magnesium ion
...
Sulphide ion, S-2 has -2 charge
...
Around the nucleus, there are 18 electrons in
sulphide ion
...
These ions are short
lived species and only exist at high temperature
...
Examples
When O2 loses an electron it forms O2⁺ ion, but when it absorbs an electron it forms O2¯ ion
...
Similarly N2¯and N2⁺ etc are examples of molecular ions of N2 gas
...
A molecule is made up of atoms of one or more elements
...
In a molecule, the
atoms are combined in a certain fixed ratio
...
2
...
When electron/s
are removed, the ion gains a net positive charge, while addition of electrons will give a net negative
charge to the molecular ion
...
3
...
In
comparison, a molecular ion is either positively charged or negatively charged, depending on whether it
gained or lost electron/s
...
Molecule is a stable unit while molecular ion is reactive specie
...
Some substances like halogens when exposed to sun light, their molecules split up into free radicals
...
For e
...
,
Dot (
...
Contact: ssva015@gmail
...
A
...
#
Free Radical
1
A free radical is an atom which has an
unpaired (having odd number) electron
and bears no electric charge
...
6
7
Free radicals are not charged species even
if they have unpaired electrons
In a free radical, the number of electrons is
equal to the number of protons
Ion
Ion is an atom or group of atoms having a charge
on it
...
Ions always hold a charge
In an ion, the total number of electrons is always
not equal to the number of protons in the nucleus
SELF ASSESSMENT EXERCISE 1
...
For instance water exists as
molecules, carbon exists as atoms
...
Molecule
Smallest particle of a covalent compound or an element which can exist independently is called
molecule
...
A covalent compound is made when two or more nonmetal atoms bond by sharing valence electrons
...
com
Page 14
Chapter 1
Chemistry 9th Notes By F
...
Khan
monoatomic
molecule
polyatomic
Monoatomic Molecule
A molecule that contains only one atom is called monoatomic
...
Polyatomic Molecule
Molecules that contain two or more similar or different atoms are called polyatomic molecules
...
Molecules versus Compounds
Molecules made up of two or more elements are called compounds
...
All compounds are molecules; not all molecules are compounds
...
A single oxygen, O, is not a molecule
...
g
...
g
...
Example 1
...
3 shows some molecules
...
Solution
“Elements have atoms of same sizes and compounds have atoms of different sizes”
...
Particles of compounds are B and F
...
com
Page 15
Chapter 1
Chemistry 9th Notes By F
...
Khan
SELF ASSESSMENT EXERCISE 1
...
Observe the given figure A and identify the diagram that represents the particles of:
a) An element whose particles are atoms
...
(f)
c) A compound
...
(c)
e) A mixture of two elements
...
(e)
2
...
Answer:
i) A compound
ii) A mixture of an element and a compound
iii) A mixture of two compounds
iv)An element whose particles are molecules
v) A mixture of an element and a compound
vi) An element whose particles are atoms
Q11
...
During 600 – 1600 AD, Chemical history was dominated by a pseudo-science called alchemy
...
They searched for ways to
change less valued metals such as lead into gold
...
Therefore, the work of earlier alchemists handicapped progress of science
...
These
processes are in use today
...
This means the
works of different scientists at the same time handicap or promotes the growth of science
...
It is
denoted by NA and is equal to 6
...
Mole
A mole is an amount of a substance that contains 6
...
Mole can also be
defined as atomic mass, molecular mass or formula mass expressed in grams
...
com
Page 16
Chapter 1
Chemistry 9th Notes By F
...
Khan
Relation between mole and Avogadro’s number
...
022 x 1023
Examples:1 mole of carbon = 6
...
022 x 1023 atoms
1 mole of water = 6
...
1 mole of sodium chloride = 6
...
022 x 1023 molecules
...
02 x 1023 atoms of an element or 6
...
02 x 1023 formula
units of an ionic compound are equivalent to one mole
...
of moles x Avogadro’s number
Q12
...
The mass of one mole C-atoms is 12 g
...
How many atoms are there in 32
...
The mass of one mole S-atoms is 32
...
022 x 10 atoms in 32
...
Q14
...
No, a dozen eggs does not have same mass as dozen bananas
...
The unit for molar mass is g/mol
...
What are the molar masses of C and S?
Ans
...
1 g
...
It is also called a mole or a gram
atom
...
Is the gram atomic mass of C-atoms is 12 g?
Ans
...
Gram Molecular Mass
Molecular mass of an element or a compound expressed in grams is called gram molecular mass
...
Contact: ssva015@gmail
...
A
...
What is the mass of one mole of water molecules? Is this mass of water molecules equal
to molecular mass of water?
Ans
...
23
Q18
...
022 x 10 molecules of glucose? Is this mass of glucose molecules
equal to molecular mass of glucose?
23
Ans
...
022 x 10 molecules of glucose = 1 mole
Molecular mass of C6H12O6 = 6 x 12 + 12 x 1 +16 x 6
= 72 + 12 + 96
= 180 amu
So, gram molecular mass of C6H12O6 = 180 g
The mass of one mole of glucose molecules is 180 g and it is equal to the molecular mass of
glucose
...
It is
also called a mole
...
5 =58
...
5 g = mole of NaCl formula unit
Difference between the terms Gram Atomic Mass, Gram Molecular mass and Gram Formula Mass:1
...
2
...
022 x 1023 atoms, gram molecular mass contains 6
...
022 x 1023 formula units
...
All of these quantities represent molar mass
...
Chemical Calculations
1
...
6: Calculating mass of one mole of a substance
Calculate the molar masses of (a) Na
(b) Nitrogen
(c) Sucrose C12H22O11
Solution
(a) Mass of 1 mole of Na = 23 g
(b) Nitrogen occurs as diatomic molecules
...
com
Page 18
Chapter 1
Chemistry 9th Notes By F
...
Khan
(c) Molecular mass of C12H22O11 = 12 x 12 + 1 x 22 + 16 x 11
= 144 + 22 + 176 = 342 amu
Therefore, mass of 1 mole of sucrose = 342 g
SELF ASSESSMENT EXERCISE 1
...
5 g
(b) Iodine occurs as diatomic molecules
...
1 g
(d) Oxygen occurs as diatomic molecules
...
7: Calculating the mass of a given number of moles of a substance
Oxygen is converted to ozone (O3) during thunder storms
...
05 moles of ozone is
formed in a storm?
Problem solving strategy
Ozone is a molecular substance
...
9
...
05 moles of O3 = 48 g x 9
...
4 g of O3
Example 1
...
If 0
...
Determine its molar mass and use it to convert moles to mass in grams
...
25 moles of CO2
? g of CO2
Solution
Molar mass of CO2 = 12 + 2 x 16 = 44 g/mol
1 mole of CO2 = 44 g of CO2
So, 0
...
25 mol = 11 g of CO2
Contact: ssva015@gmail
...
A
...
9: Converting grams into moles
How many moles of each of the following substance are present?
(a) A balloon filled with 5 g of hydrogen
...
Problem solving strategy
Hydrogen and ice both are molecular substances
...
Use the molar mass of each to
convert masses in grams to moles
...
5 moles of H2
b) Mass of 1 mole of H2O
1 mole of H2O
So, 18 g of H2O
= 2 x 1 + 16
= 2 + 16
= 18 g
= 1 mole
1 g of H2O
=
100 g of H2O
=
moles
moles
= 5
...
9
1) The molecular formula of a compound used for bleaching hair is H2O2
...
5 moles
...
of moles of this compound that would exactly weigh 30 g
...
of moles
Mass of H2O2
= 34 x 2
...
com
Page 20
Chapter 1
Chemistry 9th Notes By F
...
Khan
(b) Mass of H2O2
Molar mass of H2O2
= 30 g
= 34 g/ mol
Number of moles
=
=
= 0
...
5 grams of this salt
...
Solution
Mass of NaCl
Molar mass of NaCl
= 12
...
5 =58
...
21 mol
3) Before the digestive systems X-rayed, people are required to swallow suspensions of barium sulphate
(BaSO4)
...
Solution
Mass of one mole of BaSO4 = 137 + 32 + 4(16) = 233g
2
...
10: Calculating the number of atoms in given moles
1) Zn is a silvery metal that is used to galvanize steel to prevent corrosion
...
25
moles of Zn?
Solution
1 mole of Zn contains
Number of atoms
1
...
022 x 1023 atoms
= No
...
25 x 6
...
53 x 1023 Zn atoms
2) A thin foil of Aluminum (Al) is used as wrapper in food industries
...
2 moles of Aluminium?
Solution
1 mole of Al contains
Number of atoms
0
...
com
= 6
...
of moles x Avogadro’s number
= 0
...
022 x 1023
= 1
...
A
...
11: Calculating the number of molecules in given moles of a substance
1) Methane (CH4) is the major component of natural gas
...
5 moles of a
pure sample of methane?
Solution
1 mole of CH4 contains
= 6
...
5 moles
Number of molecules
=?
Number of molecules
= No
...
5 moles of CH4 will contain= 0
...
022 x 1023
= 3
...
Sulphur dioxide reacts with water to form acid rain
...
25 moles of
SO2?
Solution
1 mole of SO2 contains
= 6
...
25 moles
Number of molecules
=?
Number of molecules
= No
...
25 moles of SO2 will contain= 0
...
022 x 1023
= 1
...
12: Calculating the number of moles in given number of atoms
Titanium is corrosion resistant metal that is used in rockets, aircrafts and jet engines
...
011 x 1023 Ti atoms
...
022 x 1023 atoms
...
011 x 1023
Number of moles
=?
= 3
...
022 x 1023
= 0
...
com
Page 22
Chapter 1
Chemistry 9th Notes By F
...
Khan
Example 1
...
Its molecular formula is CH2O
...
011 x 1022 molecules of this compound
...
022 x 1023 molecules
...
011 x 1022
Number of moles
=?
= 3
...
022 x 1023
= 0
...
10
1
...
It is used as a pain killer
...
25 x 1030 molecules
...
022 x 1023 molecules
...
25 x 1030
Number of moles
=?
= 1
...
022 x 1023
= 0
...
A method used to prevent rusting in ships and underground pipelines involves connecting the iron to a
block of a more active metal such as magnesium
...
How many moles
of magnesium are present in 1 billion (1 x 109) atoms of magnesium?
Solution
1 mole of an element contains 6
...
Number of atoms
=1 x 109
Number of moles
=?
= 1 x 109 / 6
...
1661 x 10-14 moles of Mg
Contact: ssva015@gmail
...
A
...
Elements are the building blocks of all the substances that make up all the living and non-living things
...
Water cover 70% of the earth’s crust
...
It lowers the chances of getting stomach cancer, prevents
heart disease and stroke
...
Most of its components are
made up of molecules
...
Glucose (C6H12O6) is known as blood sugar
...
Potassium Chlorate (KCIO3) is used commonly for the laboratory preparation of O gas
...
All compounds are molecules; not all molecules are compounds
...
Encircle the correct answer:(i) Which of the following lists contains only elements?
(a) Air, water, oxygen
(b) Hydrogen, oxygen, brass
(c) Air, water, fire, earth
(d) Calcium, sulphur, carbon
(ii) The diagrams below represent particles in four substances, which box represent the particles in nitrogen
...
5H2O
...
5, S=32, O=16, H=1)
(a) 159
...
5
(c) 249
...
5
(iv) A compound with chemical formula Na2CX3 has formula mass 106 amu
...
5
(c) 0
...
05
(vi) What is the mass of 4 moles of hydrogen gas?
(a) 8
...
032 g
(c) 1 g
(d) 1
...
com
(d) 44 g
Page 24
Chapter 1
Chemistry 9th Notes By F
...
Khan
(viii) The electron configuration of an element is 1s22s2
...
5X
(c) 2X
(d) 1
...
5H2O = 63
...
5 + 32 + 64 + 10 + 80
= 249
...
008
4 moles of H2 = 4 x 2 x 1
...
064g
(vii) CO2 = 44g ;
let Carbon be X
X + 2(16) = 44g
X + 32 = 44g
X = 44 – 32
X = 12g
(viii)
(ix) Because O2 and H2O have molecules
(x) 1 mole of C = 12g = x atoms
1 mole of Mg = 24g = x atoms
12 g of Mg = 0
...
So, 12 g of Mg contain 0
...
Give short answers:(i) Differentiate between an ion and a free radical?
Ans: See in notes page 14
...
(iii) Differentiate between analytical chemistry and environmental chemistry
...
(iv) What is a mole?
Ans: A mole is an amount of a substance that contains 6
...
This experimentally determined number is known as Avogadro’s number
...
Number of moles of a substance =
For example:1 mole of carbon (C) = 12 g of carbon = 6
...
Contact: ssva015@gmail
...
A
...
0 g of steam?
Ans: Mass in grams = 9
...
(viii) Why one mole of hydrogen molecules and one mole of H-atoms have different masses?
Ans: One mole of hydrogen molecules and one mole of H-atoms have different masses because there are two Hatoms present in one molecule of hydrogen (H2)
...
Atomic mass of H-atom = 1
...
008 g
Molecular mass of H2 = 2 x 1
...
016 amu
1 mole of H2 = 2
...
Define ion, molecular ion, formula unit, free radical, atomic number, mass number, atomic mass
unit?
Ans: See in notes, pages 6, 7, 10, 12, and 13
...
Differentiate between (a) atom and ion, (b) molecular ion and free radical?
Ans: Difference between an atom and an ion:Atom
It is the smallest particle of an element
...
It is a neutral particle
...
It has positive or negative charge on it
...
Molecular ions do not form ionic compounds
...
com
Ion
It is the smallest particle of an ionic substance
...
It has either positive or negative charge on it
...
It is electrically neutral
...
It have tendency to complete its octet by gaining or
losing electrons
...
A
...
Describe how Avogadro’s number is related to a mole of any substance
...
The number of atoms, ions or molecules present in one mole of a substance is called Avogadro’s number
...
022 x 1023
...
022 x 1023
particles of that substance
...
Relation between mole and Avogadro’s number
...
02 x 1023
Examples:1 mole of carbon = 6
...
022 x 1023 atoms
1 mole of water = 6
...
1 mole of sodium chloride = 6
...
022 x 1023 molecules
...
02 x 1023 atoms of an element or 6
...
02 x 1023 formula
units of an ionic compound are equivalent to one mole
...
of moles x Avogadro’s number
6
...
4 g of He
Solution:
(b) 250mg of Carbon
Solution:
Contact: ssva015@gmail
...
A
...
5kg of MgO
Solution:
7
...
2 moles of K
Solution:
Contact: ssva015@gmail
...
25 moles of steam
Solution:
Chemistry 9th Notes By F
...
Khan
( )
( )
(d) 1
...
5H2O
Solution:
(e) 0
...
com
(
( )
(
)
( )( )
(
)
)
Page 29
Chapter 1
Chemistry 9th Notes By F
...
Khan
8
...
5 moles of carbon dioxide
Solution:
Number of molecules = No
...
4 moles of ammonia, NH3
Solution:
Number of molecules = No
...
09 moles of benzene, C6H6
Solution:
Number of molecules = No
...
01 moles of acetic acid, CH3COOH
Solution:
Number of molecules = No
...
Decide whether or not each of the following is an example of empirical formula:
(a) Al2Cl6
It is a molecular formula
...
(d) C2H6O
Yes, it is an empirical formula
...
TNT or trinitrotoluene is an explosive compound used in bombs
...
Write its empirical formula
...
Molecular formula of TNT = C7H5N3O6
Empirical formula of TNT = C7H5N3O6
Contact: ssva015@gmail
...
A
...
A molecule contains four phosphorus atoms and ten oxygen atoms
...
Also determine the molar mass of this molecule?
Ans
...
Indigo (C16H10N2O2), the dye used to color blue jeans is derived from the compound known as
indoxyl (C8H7ON)
...
Also write their empirical
formulas?
Ans
...
Identify the substance that has formula mass of 133
...
AlCl3 has the formula mass of 133
...
(a) MgCl2
Formula mass of MgCl2 = 24 + 2(35
...
5)
= 64 + 71
= 135 amu
(c) BCl3
Formula mass of BCl3 = 11 + 3(35
...
5
= 117
...
5)
= 27 + 106
...
5 amu
14
...
3
...
4
Contact: ssva015@gmail
...
A
...
23g of Na
Solution
c
...
Calculate the mass of following:a
...
24 x 1018 atoms of iron
Solution
(
)
b
...
com
Page 32
Chapter 1
Chemistry 9th Notes By F
...
Khan
c
...
3 x 106 atoms of Al
Solution:
16
...
A cornstalk grows from a seed
...
Biochemistry, since cornstalk is a plant
...
Dynamite (C3H5N3O9) explodes to form a mixture of gases
...
Organic Chemistry, since dynamite is an organic compound
...
Purple iodine vapour appears when solid iodine is warmed
...
Physical Chemistry, since changes of matter is studied in Physical Chemistry
...
Gasoline (a mixture of hydrocarbons) fumes are ignited in an auto mobile engine
...
Organic Chemistry, since hydrocarbons are organic compounds
...
A silver article tarnishes in air
...
Inorganic Chemistry, since silver is an inorganic compound
...
com
Page 33
Chapter 1
Chemistry 9th Notes By F
...
Khan
f
...
Ans
...
g
...
Ans
...
h
...
Ans
...
i
...
Ans
...
j
...
Ans
...
Contact: ssva015@gmail
...
A
...
What mass of sodium metal contains the same number of atoms as 12
...
12g of C = 1 mole of carbon
1 mole of C = 12
...
022 x 1023 particles
The molar mass of sodium = 23
...
0g of Na = 6
...
What mass of oxygen contains the same number of molecules as 42g of nitrogen?
Ans
...
Q3
...
1 mole of H = 6
...
022 x 1023 atoms of H = 1
...
008
Contact: ssva015@gmail
...
A
...
Observe the given figure
...
a) Count the substances shown in the sample?
There are 5 substances
...
It contains elements and compounds
...
N2 (nitrogen), O2 (oxygen), Ar (argon), CO2 (carbon dioxide), H2O (water)
...
e) What is the most common substance in air?
The most common substance in air is N2
...
Calculate the number of H-atoms present in 18g of H2O?
Ans
...
Mass of 1 mole of H2O = 2(1) + 16 = 18g
Number of molecules in 18g of H2O = 6
...
022 x 1023
= 12
...
204 x 1024
Q6
...
Number of molecules in 18g of H2O = 6
...
022 x 1023
= 18
...
8066 x 1024
Contact: ssva015@gmail