Hydrated cobalt (II) chloride decomposes on heating. The equation for the reaction is CoCl2.6H2O → CoCl2 + 6H2O. The reaction is reversed by adding water. Which row describes the color change and the type of reaction for the reverse reaction?
A. Colour change - blue to pink, type of reaction - endothermic
B. Colour change – blue to pink, type of reaction – exothermic
C. Colour change – pink to blue, type of reaction – endothermic
D. Colour change – pink to blue, type of reaction - exothermic

To solve this problem, let's first analyze the reaction step by step.

### Reaction Description:
1. **Heating Hydrated Cobalt(II) Chloride:**
- The equation is:
\[
\text{CoCl}_2 \cdot 6\text{H}_2\text{O} \xrightarrow{\text{heat}} \text{CoCl}_2 + 6\text{H}_2\text{O}
\]
- The **hydrated** form of cobalt(II) chloride (\(\text{CoCl}_2 \cdot 6\text{H}_2\text{O}\)) is **pink**.
- When you heat it, water molecules are removed, and **anhydrous** cobalt(II) chloride (\(\text{CoCl}_2\)) is formed, which is **blue**.
- So, on heating, the color change is from **pink to blue**.

2. **Reverse Reaction (Adding Water):**
- When water is added back to the anhydrous blue \(\text{CoCl}_2\), it gets hydrated again, turning into \(\text{CoCl}_2 \cdot 6\text{H}_2\text{O}\), which is pink.
- The reverse reaction involves the **color change from blue to pink**.
- This reverse reaction occurs when water is added, and heat is **released**, indicating that the reverse reaction is **exothermic**.

### Explanation of Choices:
- **A. Color change – blue to pink, type of reaction – endothermic:** Incorrect, because the reverse reaction (hydration) is **exothermic**, not endothermic.
- **B. Color change – blue to pink, type of reaction – exothermic:** Correct. When water is added, the color changes from blue to pink, and the reaction is exothermic.
- **C. Color change – pink to blue, type of reaction – endothermic:** Incorrect, this describes the forward reaction, not the reverse.
- **D. Color change – pink to blue, type of reaction – exothermic:** Incorrect, the forward reaction (dehydration) is **endothermic**.

### Conclusion:
The correct answer is **B. Color change – blue to pink, type of reaction – exothermic**.