Explaining what's happening
2 marks · EasyIn a reaction, there are 40 effective collisions per minute at the start. After some time, the number of effective collisions drops to 12 per minute.
Calculate how many times faster the reaction was at the start compared to later. Give your answer as a number.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
3.33 (±0.02)
Also accept: 3.3; 10/3
Common mistakes: Subtracting instead of dividing
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Selects correct method: divides initial rate by later rate.
A1 · 1 mark · Gives correct quotient, e.g. 3.33 or 10/3 or 3.3 (within ±0.02). (follow-through)
Worked solution
Initial rate = 40 collisions/min
Later rate = 12 collisions/min