A student carries out an experiment to investigate the temperature change during the chemical reaction between dilute nitric acid and potassium hydroxide solution.
The diagram shows the experimental setup used by the student:
(i) Identify the equipment labeled A, B, and C in the diagram. (ii) State one modification the student can make to this apparatus to obtain a more accurate measurement of the temperature change.
The student adds the potassium hydroxide solution, 4 cm34\text{ cm}^34 cm3 at a time, to the dilute nitric acid in the beaker. The table below shows the recorded temperatures.
| Volume of potassium hydroxide solution added (cm3\text{cm}^3cm3) | Temperature (∘C^\circ\text{C}∘C) |
|---|---|
| 0 | 16.5 |
| 4 | 18.5 |
| 8 | 21.0 |
| 12 | 23.5 |
| 16 | 25.0 |
| 20 | 23.5 |
| 24 | 21.5 |
(i) Describe how the temperature of the reaction mixture changes as the potassium hydroxide solution is added. (ii) Explain how these results demonstrate that the reaction is exothermic.
The activation energy for this neutralization reaction is relatively low. State the meaning of the term activation energy.