AQA GCSE Chemistry Paper 2
Questions & Answers
How do you measure the rate of a reaction? - ANSWERSBy 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? - ANSWERSMean 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? - ANSWERSMean rate of reaction = quantity of product
formed/time taken
What units can you measure the rate of a reaction in? - ANSWERSg/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? - ANSWERSBy 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? -
ANSWERSConcentration 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? -
ANSWERSCollision theory
What is collision theory? - ANSWERSChemical reactions can occur only when reacting
particles collide with each other and with sufficient energy
What is the activation energy of a reaction? - ANSWERSThe 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? - ANSWERSIt 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? - ANSWERSIt 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? - ANSWERSIt 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? - ANSWERSIt 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? - ANSWERSGrind 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? - ANSWERSIt doubles it
What is a catalyst? - ANSWERSA 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? - ANSWERSBy 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? -
ANSWERSIt is not included in the chemical equation for the reaction
What is a reversible reaction? - ANSWERSWhere 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? - ANSWERS
How can you change the direction of a reversible reaction? - ANSWERSBy changing
the conditions; for example heating or cooling the reaction
Describe the energy changes in a reversible reaction - ANSWERSOne 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? - ANSWERSWhen 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? - ANSWERSThe conditions
, What happens to an equilibrium if any of the conditions change? - ANSWERSThe
system responds to counteract the change
What does Le Chatelier's principle predict? - ANSWERSThe 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? - ANSWERSThe system will no longer be in
equilibrium and the concentration of all the substances will change until equilibrium is
reached again
What happens when the concentration of a reactant is increased in a reversible
reaction? - ANSWERSMore products will be formed until equilibrium is reached again
What happens when the concentration of a product is decreased in a reversible
reaction? - ANSWERSMore reactant will react until equilibrium is reached again
What happens when the temperature of a system in equilibrium is increased? -
ANSWERSThe relative amount of products at equilibrium increases for an endothermic
reaction OR The relative amount of products at equilibrium decreases for an exothermic
reaction
What happens when the temperature of a system in equilibrium is decreased? -
ANSWERSThe relative amount of products at equilibrium decreases for an endothermic
reaction OR The relative amount of products at equilibrium increases for an exothermic
reaction
What happens in gaseous reactions when the pressure of a system in equilibrium is
increased? - ANSWERSThe equilibrium position shifts towards the side with the smaller
number of molecules as shown by the symbol equation for the reaction
What happens in gaseous reactions when the pressure of a system in equilibrium is
decreased? - ANSWERSThe equilibrium position shifts towards the side with the larger
number of molecules as shown by the symbol equation for the reaction
Where is crude oil found? - ANSWERSIn rocks
What is crude oil formed from? - ANSWERSThe remains of an ancient biomass
consisting mainly of plankton that was buried in mud
What chemically is crude oil? - ANSWERSA mixture of a large number of compounds;
mainly hydrocarbons
What is a hydrocarbon? - ANSWERSA molecule made up of carbon and hydrogen only
Questions & Answers
How do you measure the rate of a reaction? - ANSWERSBy 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? - ANSWERSMean 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? - ANSWERSMean rate of reaction = quantity of product
formed/time taken
What units can you measure the rate of a reaction in? - ANSWERSg/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? - ANSWERSBy 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? -
ANSWERSConcentration 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? -
ANSWERSCollision theory
What is collision theory? - ANSWERSChemical reactions can occur only when reacting
particles collide with each other and with sufficient energy
What is the activation energy of a reaction? - ANSWERSThe 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? - ANSWERSIt 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? - ANSWERSIt 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? - ANSWERSIt 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? - ANSWERSIt 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? - ANSWERSGrind 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? - ANSWERSIt doubles it
What is a catalyst? - ANSWERSA 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? - ANSWERSBy 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? -
ANSWERSIt is not included in the chemical equation for the reaction
What is a reversible reaction? - ANSWERSWhere 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? - ANSWERS
How can you change the direction of a reversible reaction? - ANSWERSBy changing
the conditions; for example heating or cooling the reaction
Describe the energy changes in a reversible reaction - ANSWERSOne 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? - ANSWERSWhen 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? - ANSWERSThe conditions
, What happens to an equilibrium if any of the conditions change? - ANSWERSThe
system responds to counteract the change
What does Le Chatelier's principle predict? - ANSWERSThe 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? - ANSWERSThe system will no longer be in
equilibrium and the concentration of all the substances will change until equilibrium is
reached again
What happens when the concentration of a reactant is increased in a reversible
reaction? - ANSWERSMore products will be formed until equilibrium is reached again
What happens when the concentration of a product is decreased in a reversible
reaction? - ANSWERSMore reactant will react until equilibrium is reached again
What happens when the temperature of a system in equilibrium is increased? -
ANSWERSThe relative amount of products at equilibrium increases for an endothermic
reaction OR The relative amount of products at equilibrium decreases for an exothermic
reaction
What happens when the temperature of a system in equilibrium is decreased? -
ANSWERSThe relative amount of products at equilibrium decreases for an endothermic
reaction OR The relative amount of products at equilibrium increases for an exothermic
reaction
What happens in gaseous reactions when the pressure of a system in equilibrium is
increased? - ANSWERSThe equilibrium position shifts towards the side with the smaller
number of molecules as shown by the symbol equation for the reaction
What happens in gaseous reactions when the pressure of a system in equilibrium is
decreased? - ANSWERSThe equilibrium position shifts towards the side with the larger
number of molecules as shown by the symbol equation for the reaction
Where is crude oil found? - ANSWERSIn rocks
What is crude oil formed from? - ANSWERSThe remains of an ancient biomass
consisting mainly of plankton that was buried in mud
What chemically is crude oil? - ANSWERSA mixture of a large number of compounds;
mainly hydrocarbons
What is a hydrocarbon? - ANSWERSA molecule made up of carbon and hydrogen only
