revision on rates of reactions

1. Do Now:
• Write down the 5 factors that affect rate of
reaction.
• Pick one factor and explain why it affects the rate of
the reaction.
Be sure to include whether the factor affects the
chance of the reactants colliding or the chance of
collisions being successful (or both).

2. Calculating rates
LO: Use experimental data to explain changes in
reaction rates.
Key words: Catalyst, pressure, temperature,
reactants, concentration, rate

3. Explain, in terms of particles, why the rate of reaction
increases when the concentration of sodium thiosulfate is
increased. ( 2 marks)
more collisions
accept greater chance of collisions
accept collide more successfully
ignore references to energy / speed of particles / surface area
1
more particles (in each volume of solution)(i.e. an attempt at
defining concentration)
accept ‘particles are closer together’
allow ions / atoms / molecules for particles ignore reactants
accept greater frequency of collisions or greater number of collisions per
second for 2 marks
1

4. Use your understanding to explain the results
• There are 5 different experimental methods
with their results.
• For each station you will need to work out
which factor that has been changed and
answer the questions.
• You must complete three.
(You only need to sketch the graphs)

5. Calculating rates of reaction
What do I mean by the “rate of reaction”?
How can I calculate the rate of the reaction?

6. A student studied the reaction between dilute hydrochloric acid and an excess of
calcium carbonate.
calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
The student measured the volume of carbon dioxide produced in the experiment. The
results are shown on the graph.
(a) After how many minutes had all the acid been used up?
(b) The student wrote this conclusion for the experiment:
‘The reaction gets slower and slower as the time increases.’
Explain why the reaction gets slower. Your answer should be in terms of particles.

7. 6
accept 5.8 – 6 1
(b) hydrochloric acid used up / reacted / combined / or fewer particles
(of hydrochloric acid) or fewer hydrogen ions owtte
accept reactants used up
accept less calcium carbonate or
smaller surface area of calcium carbonate
accept lower concentration / less crowded
do not accept atoms / molecules
ignore references to energy
do not accept references to atoms or molecules
1
fewer collisions owtte
independent mark 1