Question 19M.3.sl.TZ1.2b(iv)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.3.sl.TZ1.2b(iv) |
| Level | sl | Paper | 3 | Time zone | TZ1 |
| Command term | Predict | Question number | b(iv) | 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.
Predict, giving a reason, how the final enthalpy of reaction calculated from this experiment would compare with the theoretical value.
[1]
lower/less exothermic/less negative AND heat loss/some heat not accounted for
OR
lower/less exothermic/less negative AND mass of reaction mixture greater than 25.00 g
OR
greater/more exothermic /more negative AND specific heat of solution less than water [✔]
Note: Accept “temperature is lower” instead of “heat loss”.
Accept “similar to theoretical value AND heat losses have been compensated for”.
Accept “greater/more exothermic/more negative AND linear extrapolation overestimates heat loss”.
Only about a third of the students correctly deduced that loss of heat to the environment means that the experimental value is lower than the theoretical one, though other answers, such as “higher because linear extrapolation over-compensates for the heat losses” were also accepted.
