Question 17N.2.hl.TZ0.1
| Date | November 2017 | Marks available | [Maximum mark: 5] | Reference code | 17N.2.hl.TZ0.1 |
| Level | hl | Paper | 2 | Time zone | TZ0 |
| Command term | Determine, Estimate, Suggest | Question number | 1 | Adapted from | N/A |
A student titrated two acids, hydrochloric acid, HCl (aq) and ethanoic acid, CH3COOH (aq), against 50.0 cm3 of 0.995 mol dm–3 sodium hydroxide, NaOH (aq), to determine their concentration. The temperature of the reaction mixture was measured after each acid addition and plotted against the volume of each acid.
Using the graph, estimate the initial temperature of the solutions.
[1]
21.4 °C
Accept values in the range of 21.2 to 21.6 °C.
Accept two different values for the two solutions from within range.
Determine the maximum temperature reached in each experiment by analysing the graph.
[2]
HCl: 30.4 «°C»
Accept range 30.2 to 30.6 °C.
CH3COOH: 29.0 «°C»
Accept range 28.8 to 29.2 °C.
Suggest why the enthalpy change of neutralization of CH3COOH is less negative than that of HCl.
[2]
CH3COOH is weak acid/partially ionised
energy used to ionize weak acid «before reaction with NaOH can occur»
