An alkaline earth metal gives a salt with chlorine which is sparingly soluble in water at room tempreture but fairly soluble in boiling water. It also forms a sulphate whose mixture with a sulphate of a transition metal is called 'lithopone' and is used as white pigment. the alkaline earth metal is

Options

A. `Ca`
B. `Mg`
C. `Sr`
D. `Ba`

Explanation

To solve the question, we need to identify the alkaline earth metal based on the given characteristics of the salt it forms with chlorine and its sulfate.

### Step-by-Step Solution:

1. **Identify the Characteristics of the Salt:**
- The salt formed with chlorine is described as sparingly soluble in water at room temperature but fairly soluble in boiling water. This suggests that the salt has low solubility at lower temperatures but increases in solubility with temperature.

2. **Consider Possible Alkaline Earth Metals:**
- The alkaline earth metals include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). We need to evaluate which of these metals could form a salt that meets the solubility criteria.

3. **Evaluate Barium Chloride:**
- Barium (Ba) is known to form barium chloride (BaCl2), which is sparingly soluble in cold water but more soluble in hot water. This matches the description given in the question.

4. **Identify the Sulfate:**
- The question also mentions that the alkaline earth metal forms a sulfate that, when mixed with a transition metal sulfate, is called lithopone. Barium sulfate (BaSO4) is known to be insoluble in water, which aligns with the information provided.

5. **Confirm the Composition of Lithopone:**
- Lithopone is a mixture of barium sulfate (BaSO4) and zinc sulfate (ZnSO4). This confirms that barium is indeed the alkaline earth metal in question.

6. **Conclusion:**
- Based on the characteristics of the salt and the sulfate, we conclude that the alkaline earth metal is **Barium (Ba)**.

### Final Answer:
The alkaline earth metal is **Barium (Ba)**.

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