AQA GCSE Chemistry - Paper 2
Mean rate of reaction (with reactant) - correct answer ✔Rate of reaction:
Quantity of reactant used
----------------------------
Time taken
Mean rate of reaction (with product) - correct answer ✔Rate of reaction:
Quantity of product formed
----------------------------
Time taken
Measurements for quantity of product or reactant - correct answer ✔Either
as mass in g or as volume in cm³
Measurements for the rate of reaction - correct answer ✔Either as g/s, cm³/s,
or mol/s
Factors which affect rate of chemical reaction - correct answer ✔-
*Temperature*: a faster temperature means faster reaction
- *Concentration / pressure*: a higher concentration or pressure means a
faster reaction
- *Surface area*: a larger surface area: volume ratio means a faster reaction
- *Catalysts*: a reaction in the presence of a catalyst is faster
,Collision theory - correct answer ✔This states that a chemical reaction can
only happen when reacting particles collide with each other with enough
energy.
Activation energy - correct answer ✔This is the minimum energy required for
a reaction to take place.
How surface area, concentration or pressure changes rate of reaction in terms
of collision theory - correct answer ✔This increases the frequency of
collisions, as there are more particles that are able to collide, increasing rate
of reaction.
How temperature changes rate of reaction in terms of collision theory - correct
answer ✔This increases the frequency of collisions as well as the energy the
collisions have, increasing rate of reaction.
Catalysts - correct answer ✔- A catalyst is a substance that changes the rate
of reaction
- It is not used up during the reaction, and therefore does not show up in the
products or reactants
- Different reactions require different catalysts, for example an enzyme
- The catalyst does this by supplying a different pathway to the reaction that
requires a lower activation energy, shown in the picture
Reversible reactions - correct answer ✔This is a reaction in which the
products can react to produce the original reactants
A+B⇌C+D
,Example of a reversible reaction - correct answer ✔This reaction is
reversible, meaning the reactants can be heated to get the products as well as
the products can be cooled to get the reactants:
Ammonium chloride ⇌ ammonia + hydrogen chloride
Energy changes in reversible reactions - correct answer ✔If a reaction is
endothermic in one direction, it is exothermic in the other. The same amount
of energy is transferred each way.
Equilibrium in a reversible reaction - correct answer ✔If the apparatus are
set up to prevent the escape of reactants or products, an equilibrium can be
reached, in which the rate of forward and reverse reactions are the same. This
will always occur in consistent conditions.
The effect of changing concentration in a reversible reaction - correct answer
✔When the concentration of one product or reactant is changed, the system is
no longer at equilibrium:
- If the concentration of the reactants is increased, more products are formed
until a balance is reached
- If the concentration of the products is increased, more reactants will form
until a balance is reached
The effect of increasing temperature in a reversible reaction - correct answer
✔When the temperature is *increased*:
- More product is formed for an endothermic reaction
- Less product is formed for an exothermic reaction
The effect of decreasing temperature in a reversible reaction - correct answer
✔When the temperature is *decreased*:
, - Less product is formed for an endothermic reaction
- More product is formed for an exothermic reaction
The effect of changing pressure in a reversible reaction - correct answer
✔For a gaseous reaction at equilibrium:
- An increase in pressure causes the equilibrium position to shift towards the
side of the smaller number of moles, meaning whichever side has less moles,
more of it will be formed
- A decrease in pressure causes the equilibrium position to shift towards the
side with more moles, meaning whichever side has more moles, more of it will
be formed
Hydrocarbon - correct answer ✔A hydrocarbon is a material that contains
only carbon and hydrogen atoms.
Alkanes - correct answer ✔- These are saturated, meaning there are only
single bonds between atoms
- They are relatively unreactive, although they do combust
- Their single bonds are quite strong
- They are a homologous series of hydrocarbons (organic compounds with the
same functional group and similar chemical properties)
- There are trends in their physical properties
Formula for alkanes - correct answer ✔Cn H2n+2
The first four alkanes - correct answer ✔- Methane
- Ethane
- Propane
- Butane
Mean rate of reaction (with reactant) - correct answer ✔Rate of reaction:
Quantity of reactant used
----------------------------
Time taken
Mean rate of reaction (with product) - correct answer ✔Rate of reaction:
Quantity of product formed
----------------------------
Time taken
Measurements for quantity of product or reactant - correct answer ✔Either
as mass in g or as volume in cm³
Measurements for the rate of reaction - correct answer ✔Either as g/s, cm³/s,
or mol/s
Factors which affect rate of chemical reaction - correct answer ✔-
*Temperature*: a faster temperature means faster reaction
- *Concentration / pressure*: a higher concentration or pressure means a
faster reaction
- *Surface area*: a larger surface area: volume ratio means a faster reaction
- *Catalysts*: a reaction in the presence of a catalyst is faster
,Collision theory - correct answer ✔This states that a chemical reaction can
only happen when reacting particles collide with each other with enough
energy.
Activation energy - correct answer ✔This is the minimum energy required for
a reaction to take place.
How surface area, concentration or pressure changes rate of reaction in terms
of collision theory - correct answer ✔This increases the frequency of
collisions, as there are more particles that are able to collide, increasing rate
of reaction.
How temperature changes rate of reaction in terms of collision theory - correct
answer ✔This increases the frequency of collisions as well as the energy the
collisions have, increasing rate of reaction.
Catalysts - correct answer ✔- A catalyst is a substance that changes the rate
of reaction
- It is not used up during the reaction, and therefore does not show up in the
products or reactants
- Different reactions require different catalysts, for example an enzyme
- The catalyst does this by supplying a different pathway to the reaction that
requires a lower activation energy, shown in the picture
Reversible reactions - correct answer ✔This is a reaction in which the
products can react to produce the original reactants
A+B⇌C+D
,Example of a reversible reaction - correct answer ✔This reaction is
reversible, meaning the reactants can be heated to get the products as well as
the products can be cooled to get the reactants:
Ammonium chloride ⇌ ammonia + hydrogen chloride
Energy changes in reversible reactions - correct answer ✔If a reaction is
endothermic in one direction, it is exothermic in the other. The same amount
of energy is transferred each way.
Equilibrium in a reversible reaction - correct answer ✔If the apparatus are
set up to prevent the escape of reactants or products, an equilibrium can be
reached, in which the rate of forward and reverse reactions are the same. This
will always occur in consistent conditions.
The effect of changing concentration in a reversible reaction - correct answer
✔When the concentration of one product or reactant is changed, the system is
no longer at equilibrium:
- If the concentration of the reactants is increased, more products are formed
until a balance is reached
- If the concentration of the products is increased, more reactants will form
until a balance is reached
The effect of increasing temperature in a reversible reaction - correct answer
✔When the temperature is *increased*:
- More product is formed for an endothermic reaction
- Less product is formed for an exothermic reaction
The effect of decreasing temperature in a reversible reaction - correct answer
✔When the temperature is *decreased*:
, - Less product is formed for an endothermic reaction
- More product is formed for an exothermic reaction
The effect of changing pressure in a reversible reaction - correct answer
✔For a gaseous reaction at equilibrium:
- An increase in pressure causes the equilibrium position to shift towards the
side of the smaller number of moles, meaning whichever side has less moles,
more of it will be formed
- A decrease in pressure causes the equilibrium position to shift towards the
side with more moles, meaning whichever side has more moles, more of it will
be formed
Hydrocarbon - correct answer ✔A hydrocarbon is a material that contains
only carbon and hydrogen atoms.
Alkanes - correct answer ✔- These are saturated, meaning there are only
single bonds between atoms
- They are relatively unreactive, although they do combust
- Their single bonds are quite strong
- They are a homologous series of hydrocarbons (organic compounds with the
same functional group and similar chemical properties)
- There are trends in their physical properties
Formula for alkanes - correct answer ✔Cn H2n+2
The first four alkanes - correct answer ✔- Methane
- Ethane
- Propane
- Butane
