Paper 2 Revision

Question 1

Collision theory

Answer 1

For a chemical reaction to happen:

• Reactant particles must collide with each other
• The particles must have enough energy to react

Question 2

Rate of reaction formula

Answer 2

Rate of reaction = Change in mass or volume / time taken

Question 3

Factors affecting rate of reaction

Answer 3

Pressure and concentration
Surface area
Catalysts
Temperature

Question 4

Required practical - Measuring the volume of a gas produced

Answer 4

1) Support a gas syringe with a stand, boss and clamp
2) Using a measuring cylinder, measuring 50cm^3 of hydrochloric flask and put into conical flask.
3) Add Calcium carbonate to the conical flask and connect syringe to the flask and start a stopwatch.
4) Every 10 seconds, record volume of gas produced
5) Repeat experiment with difference HCl concentrations.

Question 5

Required practical - Rate of reaction by colour change

Answer 5

Measure 50cm^3 of sodium thiosulphate using a measuring cylinder and pour into conical flask.
Put the Conical flask on a white tile with a black cross drawn.
Add 10cm^3 of hydrochloric acid to the conical flask and swirl the flask using thermometer and start stopwatch.
When the cross is no longer visible, record time taken and temperature of reacted mixture.
Repeat steps 1 to 5 with different temperatures of sodium thiosulphate.

Question 6

Reversible reaction

Answer 6

When the products can react back into the original reactants.

Question 6

Dynamic equilibrium

Answer 6

The rate of forward reaction is equal to the rate of backwards reaction.

Question 7

Equilibrium

Answer 7

When there is no net change in the concentrations of the reactants or products.

Question 7

Effect of concentration on reactants and products - reversible reactions

Answer 7

Increasing concentration of reactants means more products will be formed until equilibrium is reached.
Decressing concentration of products, means more reactants will react until equilibrium reached.

Question 8

How was crude oil formed?

Answer 8

Microscopic plants and animals die and fall to the seabed.
Layers of sand and mud fall on top.
High pressure and high temperatures causes oil to form.
Oil obtained by drilling.

Question 9

Formation of Kerogen

Answer 9

Kerogen is formed from marine algae which turns into oil and gas when heat and pressure is applied

Question 10

Alkane and Alkene formula

Answer 10

Alkane is 2n+2

Alkene is 2n

Question 11

Word equation for alkanes

Answer 11

Large alkane —> Alkenes + small alkane

heat and catalyst

Question 12

Crude oil is an important source of…

Answer 12

Fuels such as petrol, diesel, kerosene and heavy fuel oil.

Feedstock for the petrochemical industry

Question 13

Fractional Distillation

Answer 13

Crude oil heated to vapour before entering the column.
Long chain hydrocarbons condense at the bottom of the tower where it it hotter.
As the hydrocarbon move up the tower, they reach their boiling points and are collected as fractions of liquid on different levels.
Short chain hydrocarbons condense and are piped out at the top of the tower.

Question 14

Evolution of the Earth’s atmosphere

Answer 14

Earth cooled and thin crust formed.
Volcanoes erupted releasing CO2, Nitrogen and steam, which steam condenses to form oceans.
Algae in oceans photosynthesis to make oxygen - oxygen creates the ozone layer protecting the earth from the sun’s radiation
More complex organisms could evolve.

Question 15

Percentages of gas in the atmosphere

Answer 15

Argon 78%
Oxygen 21%
Nitrogen 0.9%
CO2 0.04%

Question 16

Changes in the atmosphere

Answer 16

Oxygen increased due to photosynthesis in plants

CO2 decreased as dissolved by oceans.

Question 17

Water Treatment

Answer 17

Remove solids using a mesh screen to separate sticks, mud, stones etc.
Pump in air to the water to remove odours and gases.
Add aluminium to consulate extra solids left.
Remaining solution separated in a clarifier and filtrated.
Chlorine kills bacteria.
PH checked and corrected to neutral.