DP Chemistry (last assessment 2024)
Question 22M.2.hl.TZ1.c(ii)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.hl.TZ1.c(ii) |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Calculate | Question number | c(ii) | Adapted from | N/A |
c(ii).
[Maximum mark: 1]
22M.2.hl.TZ1.c(ii)
Magnesium is a reactive metal often found in alloys.
A graph of the volume of gas produced by reacting magnesium with a large excess of 1 mol dm–3 hydrochloric acid is shown.
The reaction is first order with respect to HCl. Calculate the time taken, in seconds (s), for half of the Mg to dissolve when [HCl] = 0.5 mol dm–3.
[1]
Markscheme
«2×170 s» = 340 «s» ✔
Accept 320 – 360 «s».
Accept 400 – 450 «s» based on no more gas being produced after 400 to 450s.
Examiners report
Mediocre performance in calculating time from the graph for the data provided. Some wrote the rate expression, which only contains [HCl] and not mass or amount in mol Mg (as a solid, [Mg] is constant). This presented a challenge in arriving at a reasonable answer.
