Notesale: Turn your study into money

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Rates Of Reaction
Rate=The amount of new product formed every second
FOR CHEMICAL REACTIONS TO OCCUR, REACTING PARTICLES NEED TO COLLIDE
WITH ENOUGH ENERGY
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Collision with sufficient energy are called ​‘successful collisions’​
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Factors that affect the rate of reaction:
➔ Temperature
When temperature increases, the rate of reaction increases
Because increased temperature means that the particles are moving faster with more kinetic energy, so
more collisions will occur, and the collision will contain a higher amount of energy, resulting in a higher
probability of successful collisions
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More particles mean more
collisions, so there will be a higher chance of successful collisions
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➔ Catalyst
Catalysts speed up a reaction without getting used up
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Ways to measure rate:
★ Change in PH
★ Change in temperature
★ Volume of gas produced in a certain amount of time
★ Light intensity (color change)
★ Change in pressure
Formula to Calculate Rate:
Change in variable divided by Change in time
Graph Analysis

The graph is steepest at the beginning as the rate of reaction is fastest
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We can calculate the rate of reaction at a given point in the graph by using a tangent
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Flour Mills
Flour particles are tiny, therefore they have a large surface area, and if there is a spark from the machine,
that is enough to create an explosion
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Gas Explosions in mines
There are flammable gases in coal mines that are easily dispersed (example, methane), and so at the right
concentration, they will react and explode
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Breaking bonds require energy (activation energy)
Once the particles are broken up into individual atoms, they automatically form bonds
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In endothermic reactions, the energy required to break the bonds is more than the energy released to form
the bonds, so there is a net inflow of energy into the reaction, hence the temperature loss that normally
occurs in endothermic reactions
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This is an endothermic reactions because there is a net
inflow of energy into the reaction, and hence the products have a higher energy state than the
reactants
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Bases have a PH above 7
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Other ways of measuring PH:
PH meter-​It is a digital probe that you put into the solution without having to add indicators
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Phenolphthalein-​This indicator turns pink in the presence of alkali and colorless in acid
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PH IS CALCULATED IN LOGARITHMS, SO A LOT OF WATER HAS TO BE ADDED TO A
SOLUTION TO CHANGE THE PH
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-Temperature rises as the reaction is exothermic
-Metal disappears
Acid+Base=Salt+Water
-There will be a PH change as this is a neutralization reaction, so if there is an indicator in the solution
there will be a color change
-If the salt formed is insoluble, there will be a precipitate (solid)
Acid+Metal Carbonate=Salt+Water+Carbon Dioxide
-There will be effervescing as carbon dioxide is produced in the form of a gas
-If there is an indicator in the solution, there will be a color change as water is formed
-If the salt is insoluble, there will be a precipitate
Importance of controlling acidity in the environment:
Acid Rain

Caused by:
❖ Sulphur Dioxide-​Sulphur is an impurity in the fuel, and when the fuel burns in oxygen, sulphur
reacts with the oxygen to produce Sulphur Dioxide, and when Sulphur Dioxide is dissolved in
water, it produces Sulphuric Acid, which is a component of acid rain
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The Nitrogen Oxide then reacts with water to form Nitric acid,
which is a component of acid rain
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Moreover, natural rain is already slightly acidic because as it falls, it dissolves carbon dioxide that
is already present in the air
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Why we need to control the acidity?
Affect respiration and lung function
Can corrode structures that are made of limestone, because limestone (calcium carbonate) is alkaline
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The acidity levels affect marine life, as they are not adapted to tolerate large changes in acidity (optimum
PH for enzymes)
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The nitrates (from nitric acid) in the water is also present in fertilisers, and this can also cause
eutrophication, which is when algae grow in mass amounts until they use up all the oxygen in the water,
making the river inhabitable and anoxic
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Aluminium in soil are insoluble, but in acidic soil it is soluble, and so it is absorbed into plants and might
be toxic
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Metal Oxides are Basic
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Example:
CO2+H2O=H2CO3
Carbon Dioxide dissolves to produce Carbonic Acid

ALERT: The oxides have a PH only if they are dissolved in water, because they dissolve to produce
acidic/basic products
Neutral Oxides and Amphoteric Substances:
By name, Neutral Oxides do not have a PH, and do not react with either acids or bases
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Whereas Amphoteric substances do not have a specific PH, but they can react with both acids and bases
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Water is made of OH- and H+
The OH- component in water can react with an acid
The H+ component in water can react with alkali
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Acid+Carbonate
2
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Acid+Metal
Here are the methods of salt derivation:
❏ Insoluble reactant+acid
1
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(The reactant is insoluble, but that doesn’t mean that it
can’t react)
2
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Heat the filtrate mildly to evaporate only some water so the solution is saturated (if not, the
remaining solid is anhydrous powder, and is not a crystal)
4
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Leave to cool
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Heat the solution carefully then dry it to get salt
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❏
1
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3
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Add one solution to another in excess so the other solution has fully reacted
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Filter away the liquid so you are only left with the solid
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Wash the solid with distilled water to remove the unwanted reactant
Identifying Compounds in the Lab
Testing for Transition Metals
1
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See the color of the precipitate formed
Copper

Blue

Iron (2)

Green, then slowly becomes reddish brown upon
standing as it is oxidised to Iron (3),​ insoluble in
ammonia

Iron (3)

Reddish Brown,​ insoluble in ammonia

Zinc

White, dissolves in concentrated sodium
hydroxide and ammonia

Calcium

White, ​can be tested using flame test​ (it is
insoluble)

Aluminium

White, ​dissolved by further addition of sodium
hydroxide

Magnesium

White, ​can be tested using flame test​ (it is
insoluble)

Testing for Cations
Flame Test-​Put the solid under a bunsen flame and see what color it produces, the colors are distinctive
to the element
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Use a clean spatula, dip it in concentrated Hydrochloric acid and put in Bunsen repeatedly until
no color is produced
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(Hydrochloric Acid is used because resulting metal chloride formed is more easily vaporised)
Metal(+)+HCl=Metal Chloride+H(+)
2
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Each metal produces a characteristic color
Sodium

Orange

Potassium

Lilac

Calcium

Brick Red

Strontium

Red

Copper

Blue

Barium

Light Green

Flame colors arise because the electron becomes excited when heated and jump to a higher orbital
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Testing for Anions
CarbonatesReact it with a dilute acid, if carbonates are present in the unknown compound, when reacted with acid,
Carbon Dioxide gas should be produced
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SulphatesBarium Sulphate is a very insoluble precipitate, so add Barium Solution to the unknown compound
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NitratesAdd Sodium Hydroxide and Aluminium powder and heat gently in a warm water bath
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The presence of ammonia can be tested with Hydrochloric acid
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Testing for Halogens
Silver Halides are insoluble, so first dissolve the unknown solid in water and add an equal volume of
dilute Nitric Acid to remove impurities, then add Silver Nitrate
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Silver Chloride Precipitate will dissolve in dilute ammonia solution whilst silver bromide
will not
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Only Silver Iodide does
not
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HydrogenCombines violently with Oxygen to make water, so if there is a lit splint, the gas will burn with a squeaky
pop
OxygenIt can relight a glowing splint because there is a higher concentration of Oxygen in the test tube than in
the normal air
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One atom will gain electrons, and the other will lost electrons
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Ions with polar charges will attract and form a bond
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Crystal lattices are formed by multiple ionic bonds joined together in a regular arrangement of alternating
positive and negative ions
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However, the polar charges make them easy to
dissolve
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Covalent bonds are when atoms share electrons to achieve a full octet
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Covalent bonds are generally strong, they can’t dissolve in the water because of the nature
of their shared electron pair(s)-each atom involved in the bond depends on that electron pair for a full
octet
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They are very hard to dissolve, as the shared electron
pair makes the bonds very firm and strong, however, they are very easy to melt because they have
virtually no intermolecular forces whatsoever
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Different atoms have different electronegativity (different ability to
attract electrons), and this means the electron cloud is shifted towards a particular atom, making it not as
strong
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Uses
Limestone

Statues, cement, concrete, mortar=cement is made
from water and powder, and add sand to make
mortar
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BUT makes money and it provides jobs



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