rates of reaction exam questions

Question 1

Explain, in terms of particles, why temperature increases the rate of this reaction.
To gain full marks in this question you should write your ideas in good English.
Put them into a sensible order and use the correct scientific words.

Answer 1

• temperature increases particles have more energy
• particles move faster
• frequency of collisions increases
• greater number of collisions per second
• fequency of sucessful collisions increases

Question 2

In this question you will be assessed on using good English, organising information clearly
and using specialist terms where appropriate.
The student investigated how the rate of this reaction changed when the concentration of
hydrochloric acid was changed.
Write a plan the student could use.
In your plan you should:
• describe how you would carry out the investigation and make it a fair test
• describe the measurements you would make

Answer 2

Examples of chemistry points made in the response could include:
Plan:
• add magnesium to acid
• time reaction / ‘count bubbles’ / measure volume of gas
• change concentration / ‘volume’ of acid
Control Variables:
• amount / mass / length / same ‘size’ of magnesium
• volume / amount of acid

Question 3

Explain why, when a reversible reaction reaches equilibrium, the reaction appears to
have stopped.

Answer 3

• forward and backward reactions occur at exactly the same rate
• quantities of reactants and products do not change