Question 19M.3.hl.TZ1.2b(i)
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.hl.TZ1.2b(i) |
| Level | hl | Paper | 3 | Time zone | TZ1 |
| Command term | Outline, State | Question number | b(i) | Adapted from | N/A |
Powdered zinc was reacted with 25.00 cm3 of 1.000 mol dm−3 copper(II) sulfate solution in an insulated beaker. Temperature was plotted against time.
The maximum temperature used to calculate the enthalpy of reaction was chosen at a point on the extrapolated (dotted) line.
State the maximum temperature which should be used and outline one assumption made in choosing this temperature on the extrapolated line.
Maximum temperature:
Assumption:
[2]
Maximum temperature:
73 «°C» [✔]
Assumption:
«temperature reached if» reaction instantaneous
OR
«temperature reached if reaction occurred» without heat loss [✔]
Note: Accept “rate of heat loss is constant” OR “rate of temperature decrease is constant”.
Stating the maximum temperature that should be used in calculations was less well answered, with answers between 63 and 65, or 78 commonly given instead of the correct answer of 73°C. Most candidates managed to score the second mark for stating “no heat loss”.
