past paper questions

Question 1

1a) A + B -> C + D (by catalyst X, reaction is exothermic)

• outline a titrimetric method that could be used to measure the change in concentration of compound A with time. compound A is an alkali, whereas other compounds are neutral. (3)

Answer 1

1- take samples at various times
2- quench with ice
3- titrate with known acid concentration

OR

2- quench with acid
3- titrate with known alkali concentration

Question 2

1b): A + B -> C + D (by catalyst X, reaction is exothermic)
- the reaction is first order wrt A

• suggest an explanation other than human error, for the two anomalous results circled on the graph. (3)

Answer 2

1- unusually high rate
2- reaction is exothermic
3- more collisions with energy > Ea