GCSE CHEMISTRY AQA PAPER 2 EXAM REVISION QUESTIONS WITH
VERIFIED SOLUTIONS LATEST 2025 UPDATE.
Describe the Haber process (reversible reaction) - ANSWER- Purified gases are passed over a
catalyst at 450°C and 200 atmospheres. Some of the hydrogen and nitrogen react to form ammonia
which on cooling liquifies and is removed. The remaining hydrogen and nitrogen are recycled.
Which conditions would produce the highest yield of ammonia? - ANSWER- Low temperature,
high pressure
Why does a low temperature produce a higher yield of ammonia? - ANSWER- The forward
reaction is exothermic so a lower temperature moves the equilibrium to the right to increase the
temperature making more products
Why does a high pressure increase the yield of ammonia? - ANSWER- There are fewer
molecules on the right hand side of the reaction so the equilibrium will shift to the right to reduce
the pressure
Why is a temperature of 450°C used in the Haber process? - ANSWER- It is a compromised
temperature to produce a reasonable yield of ammonia at a suitable rate
Why is a pressure of 200 atmosphere used in the Haber process? - ANSWER- To increase the
yield of ammonia without incurring the very high energy and equipment costs for achieving very
high pressures
What effect does using a catalyst have on the yield of ammonia in the Haber process? - ANSWER-
None. It just reduces the time for the system to reach equilibrium.
What types of compounds are used in artificial fertilisers? - ANSWER- Compounds of
nitrogen, phosphorus and potassium are used to make NPK fertilisers
,What are NPK fertilizers? - ANSWER- Formulations of various salts containing appropriate
percentages of the elements (nitrogen, phosphorus and potassium)
Name the salts that are used to provide nitrogen, phosphorus and potassium in fertilisers -
ANSWER- Ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4), ammonium
phosphate ((NH3)3 PO3), potassium nitrate (KNO3)
What is ammonia used to manufacture? - ANSWER- Ammonium salts and nitric acid
Where are potassium salts obtained from for fertilisers? - ANSWER- By mining
How do you measure the rate of a reaction? - ANSWER- By measuring the quantity of a
reactant used or the quantity of product formed over time
What is the equation for calculating the mean rate of a reaction by measuring the amount of
reactant used? - ANSWER- Mean rate of reaction = quantity of reactant used/time taken
What is the equation for calculating the mean rate of a reaction by measuring the amount of product
formed? - ANSWER- Mean rate of reaction = quantity of product formed/time taken
What units can you measure the rate of a reaction in? - ANSWER- g/s or cm3/s or mol/s
How do you calculate the rate of a reaction at a specific time from graph of the quantity of reactant
used or the quantity of product formed? - ANSWER- By measuring the gradient of a tangent
drawn at that specific time on the graph
What are the five factors that can affect the rate of a reaction? - ANSWER- Concentration of
reactants in solution, pressure of reacting gases, surface area of solid reactants, temperature and
the presence of a catalyst
What theory can we use to explain how various factors affect the rate of a reaction? - ANSWER-
Collision theory
, What is collision theory? - ANSWER- Chemical reactions can occur only when reacting
particles collide with each other and with sufficient energy
What is the activation energy of a reaction? - ANSWER- The minimum amount of energy that
particles must have to react
According to collision theory why does increasing concentration of reactant in solution increase
the rate of the reaction? - ANSWER- It increases the frequency of collisions and so increases
the rate of reaction
According to collision theory why does increasing the pressure of reacting gases increase the rate
of the reaction? - ANSWER- It increases the frequency of collisions and so increases the rate
of reaction
According to collision theory why does increasing the surface area of solid reactants in solution
increase the rate of the reaction? - ANSWER- It increases the frequency of collisions and so
increases the rate of reaction
According to collision theory why does increasing temperature increase the rate of the reaction? -
ANSWER- It increases the frequency of collisions and makes the collision more energetic and
so increases the rate of reaction
How do you increase the surface area of a solid reactant? - ANSWER- Grind it into a powder
that has smaller particle size
What effect does increasing the temperature of a reaction by 10°C have on the rate of a reaction?
- ANSWER- It doubles it
What is a catalyst? - ANSWER- A chemical that changes the rate of a chemical reaction but is
not used up in the reaction
VERIFIED SOLUTIONS LATEST 2025 UPDATE.
Describe the Haber process (reversible reaction) - ANSWER- Purified gases are passed over a
catalyst at 450°C and 200 atmospheres. Some of the hydrogen and nitrogen react to form ammonia
which on cooling liquifies and is removed. The remaining hydrogen and nitrogen are recycled.
Which conditions would produce the highest yield of ammonia? - ANSWER- Low temperature,
high pressure
Why does a low temperature produce a higher yield of ammonia? - ANSWER- The forward
reaction is exothermic so a lower temperature moves the equilibrium to the right to increase the
temperature making more products
Why does a high pressure increase the yield of ammonia? - ANSWER- There are fewer
molecules on the right hand side of the reaction so the equilibrium will shift to the right to reduce
the pressure
Why is a temperature of 450°C used in the Haber process? - ANSWER- It is a compromised
temperature to produce a reasonable yield of ammonia at a suitable rate
Why is a pressure of 200 atmosphere used in the Haber process? - ANSWER- To increase the
yield of ammonia without incurring the very high energy and equipment costs for achieving very
high pressures
What effect does using a catalyst have on the yield of ammonia in the Haber process? - ANSWER-
None. It just reduces the time for the system to reach equilibrium.
What types of compounds are used in artificial fertilisers? - ANSWER- Compounds of
nitrogen, phosphorus and potassium are used to make NPK fertilisers
,What are NPK fertilizers? - ANSWER- Formulations of various salts containing appropriate
percentages of the elements (nitrogen, phosphorus and potassium)
Name the salts that are used to provide nitrogen, phosphorus and potassium in fertilisers -
ANSWER- Ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4), ammonium
phosphate ((NH3)3 PO3), potassium nitrate (KNO3)
What is ammonia used to manufacture? - ANSWER- Ammonium salts and nitric acid
Where are potassium salts obtained from for fertilisers? - ANSWER- By mining
How do you measure the rate of a reaction? - ANSWER- By measuring the quantity of a
reactant used or the quantity of product formed over time
What is the equation for calculating the mean rate of a reaction by measuring the amount of
reactant used? - ANSWER- Mean rate of reaction = quantity of reactant used/time taken
What is the equation for calculating the mean rate of a reaction by measuring the amount of product
formed? - ANSWER- Mean rate of reaction = quantity of product formed/time taken
What units can you measure the rate of a reaction in? - ANSWER- g/s or cm3/s or mol/s
How do you calculate the rate of a reaction at a specific time from graph of the quantity of reactant
used or the quantity of product formed? - ANSWER- By measuring the gradient of a tangent
drawn at that specific time on the graph
What are the five factors that can affect the rate of a reaction? - ANSWER- Concentration of
reactants in solution, pressure of reacting gases, surface area of solid reactants, temperature and
the presence of a catalyst
What theory can we use to explain how various factors affect the rate of a reaction? - ANSWER-
Collision theory
, What is collision theory? - ANSWER- Chemical reactions can occur only when reacting
particles collide with each other and with sufficient energy
What is the activation energy of a reaction? - ANSWER- The minimum amount of energy that
particles must have to react
According to collision theory why does increasing concentration of reactant in solution increase
the rate of the reaction? - ANSWER- It increases the frequency of collisions and so increases
the rate of reaction
According to collision theory why does increasing the pressure of reacting gases increase the rate
of the reaction? - ANSWER- It increases the frequency of collisions and so increases the rate
of reaction
According to collision theory why does increasing the surface area of solid reactants in solution
increase the rate of the reaction? - ANSWER- It increases the frequency of collisions and so
increases the rate of reaction
According to collision theory why does increasing temperature increase the rate of the reaction? -
ANSWER- It increases the frequency of collisions and makes the collision more energetic and
so increases the rate of reaction
How do you increase the surface area of a solid reactant? - ANSWER- Grind it into a powder
that has smaller particle size
What effect does increasing the temperature of a reaction by 10°C have on the rate of a reaction?
- ANSWER- It doubles it
What is a catalyst? - ANSWER- A chemical that changes the rate of a chemical reaction but is
not used up in the reaction
