Which of the following are
exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation (crystals) of camphor

Question

Accepted Answer

Option 1 is the correct answer because it includes the processes that are exothermic, meaning they release heat.

1. **Reaction of water with quick lime (i):** This is an exothermic process. When water is added to quick lime (calcium oxide), it reacts to form calcium hydroxide. This reaction releases a significant amount of heat, making it exothermic. The chemical equation for this reaction is:
   $$
   \text{CaO (s) + H}_2\text{O (l) → Ca(OH)}_2\text{ (aq) + heat}
   $$

2. **Dilution of an acid (ii):** This is also an exothermic process. When an acid is diluted with water, the process releases heat. This is because the ions in the acid interact with water molecules, releasing energy in the form of heat. The exothermic nature of this process is why it is advised to add acid to water slowly to prevent splattering due to the heat released.

Now, let's explain why the other options are incorrect:

- **Evaporation of water (iii):** This is an endothermic process, not exothermic. During evaporation, water molecules absorb heat from the surroundings to change from liquid to gas. This absorption of heat makes the process endothermic.

- **Sublimation of camphor (iv):** Sublimation is also an endothermic process. In sublimation, a substance transitions from a solid to a gas without passing through the liquid phase. This requires the absorption of heat, making it endothermic.

Therefore, Option 1 is correct because it includes the processes that release heat (exothermic), while the other options include processes that absorb heat (endothermic).