A student investigates the temperature change when sodium hydroxide solution reacts with hydrochloric acid.
The student puts 25 cm³ of hydrochloric acid into a polystyrene cup.
The student adds sodium hydroxide solution 5 cm³ at a time. The student stirs the mixture and records the highest temperature after each addition.
The table shows the results.
| Volume of sodium hydroxide solution added (cm³) | Temperature (°C) |
|---|---|
| 0 | 19.0 |
| 5 | 22.4 |
| 10 | 25.6 |
| 15 | 28.5 |
| 20 | 31.2 |
| 25 | 31.0 |
| 30 | 29.6 |
| 35 | 28.3 |
Write the word equation for the reaction.
Calculate the maximum temperature rise.
Maximum temperature rise = ...... °C
Is this reaction exothermic or endothermic?
Explain your answer using the results.
Explain why the student uses a polystyrene cup and not a glass beaker.
The temperature falls after 20 cm³ of sodium hydroxide solution has been added.
Suggest two reasons why.
Suggest one improvement to the method so that the student can find the maximum temperature more accurately.
51 exam-style questions on OCR GCSE Chemistry 3.2 Energetics, covering 3.2.1 Exothermic and endothermic reactions and reaction profiles and 3.2.2 Calculating energy change from bond energies. Each one has a worked solution and a mark scheme showing where the marks go.