A student investigates the temperature change when dilute hydrochloric acid reacts with sodium hydroxide solution.
This is the method used.
Measure 25 cm³ of dilute hydrochloric acid into a polystyrene cup and record its temperature.
Add 25 cm³ of sodium hydroxide solution and stir.
Record the highest temperature reached.
Repeat the experiment two more times.
Give the name of the salt formed in this reaction.
Explain why the student uses a polystyrene cup rather than a glass beaker.
The table shows the student's results.
| Experiment | Start temperature / °C | Highest temperature / °C | Temperature rise / °C |
|---|---|---|---|
| 1 | 19.5 | 26.3 | 6.8 |
| 2 | 20.0 | 22.8 | 2.8 |
| 3 | 19.0 | 25.9 | 6.9 |
Give the number of the experiment with the anomalous result.
Calculate the mean temperature rise. Do not include the anomalous result.
Suggest one reason for the anomalous result.
Give two variables the student must keep the same to make the investigation a fair test.
53 exam-style questions on Edexcel GCSE Chemistry 8.2 Heat energy changes in chemical reactions, covering 8.2.1 Exothermic and endothermic changes, 8.2.2 Bond breaking, bond making and overall energy change, 8.2.3 Calculating energy change from bond energies, and 8.2.4 Activation energy and reaction profiles. Each one has a worked solution and a mark scheme showing where the marks go.