GCSE AQA SCIENCE CHEMISTRY ELITE
REVIEW STUDY GUIDE FULLY SOLVED
QUESTIONS AND DETAILED ANSWERS 2026
◉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
◉How do catalysts increase the rate of a reaction? Answer: By
providing a different pathway for the reaction that has a lower activation
energy
◉How do you know in a reaction that a chemical is used in a reaction is
a catalyst? Answer: It is not included in the chemical equation for the
reaction
◉What is a reversible reaction? Answer: Where the products of a
chemical reaction can react to produce the original reactants
◉What is the symbol used in reversible reaction equations that shows
that the reaction is reversible? Answer:
, ◉How can you change the direction of a reversible reaction? Answer:
By changing the conditions; for example heating or cooling the reaction
◉Describe the energy changes in a reversible reaction Answer: One
direction will be exothermic and the other direction endothermic
◉When is equilibrium in a reversible reaction achieved in apparatus
which prevents the escape of reactants and products? Answer: When the
rate of the forward and reverse reactions occur at exactly the same rate
◉What affects the relative amount of all the reactants and products at
equilibrium in a reversible reaction? Answer: The conditions
◉What happens to an equilibrium if any of the conditions change?
Answer: The system responds to counteract the change
◉What does Le Chatelier's principle predict? Answer: The effects of
changing conditions on a system at equilibrium
◉What affect will changing the concentration of one of the reactants in a
reversible reaction have on the equilibrium? Answer: The system will
no longer be in equilibrium and the concentration of all the substances
will change until equilibrium is reached again
REVIEW STUDY GUIDE FULLY SOLVED
QUESTIONS AND DETAILED ANSWERS 2026
◉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
◉How do catalysts increase the rate of a reaction? Answer: By
providing a different pathway for the reaction that has a lower activation
energy
◉How do you know in a reaction that a chemical is used in a reaction is
a catalyst? Answer: It is not included in the chemical equation for the
reaction
◉What is a reversible reaction? Answer: Where the products of a
chemical reaction can react to produce the original reactants
◉What is the symbol used in reversible reaction equations that shows
that the reaction is reversible? Answer:
, ◉How can you change the direction of a reversible reaction? Answer:
By changing the conditions; for example heating or cooling the reaction
◉Describe the energy changes in a reversible reaction Answer: One
direction will be exothermic and the other direction endothermic
◉When is equilibrium in a reversible reaction achieved in apparatus
which prevents the escape of reactants and products? Answer: When the
rate of the forward and reverse reactions occur at exactly the same rate
◉What affects the relative amount of all the reactants and products at
equilibrium in a reversible reaction? Answer: The conditions
◉What happens to an equilibrium if any of the conditions change?
Answer: The system responds to counteract the change
◉What does Le Chatelier's principle predict? Answer: The effects of
changing conditions on a system at equilibrium
◉What affect will changing the concentration of one of the reactants in a
reversible reaction have on the equilibrium? Answer: The system will
no longer be in equilibrium and the concentration of all the substances
will change until equilibrium is reached again
