Superphosphate of lime is

Options

A. A mixture of normal calcium phosphate and gypsum
B. A mixture of primary calcium phosphate and gypsum
C. Normal calcium phosphate
D. Soluble calcium phosphate

Answer

To solve the question "Superphosphate of lime is," we need to analyze the options provided and understand what superphosphate of lime actually is.

### Step-by-Step Solution:

1. **Understanding Superphosphate of Lime**:
- Superphosphate of lime is a chemical fertilizer that is produced by treating rock phosphate with sulfuric acid (H2SO4) or phosphoric acid (H3PO4).

2. **Chemical Reaction**:
- The reaction can be represented as:
\[ \text{Ca}_3(\text{PO}_4)_2 + \text{H}_2\text{SO}_4 + \text{H}_2\text{O} \rightarrow \text{Ca(H}_2\text{PO}_4)_2 \cdot 2\text{H}_2\text{O} + \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \]
- Here, \(\text{Ca}_3(\text{PO}_4)_2\) is calcium phosphate, and the products are calcium dihydrogen phosphate (which is a primary calcium phosphate) and gypsum (calcium sulfate dihydrate).

3. **Identifying the Components**:
- From the reaction, we see that superphosphate of lime consists of:
- Calcium dihydrogen phosphate (primary calcium phosphate)
- Gypsum (calcium sulfate)

4. **Analyzing the Options**:
- **Option A**: Mixture of normal calcium phosphate and gypsum - **Incorrect**. This does not accurately describe superphosphate of lime.
- **Option B**: Mixture of primary calcium phosphate and gypsum - **Correct**. This accurately describes the components of superphosphate of lime.
- **Option C**: Normal calcium phosphate - **Incorrect**. Superphosphate is not just normal calcium phosphate.
- **Option D**: Soluble calcium phosphate - **Incorrect**. While superphosphate is soluble, it is specifically a mixture of primary calcium phosphate and gypsum.

5. **Conclusion**:
- The correct answer is **Option B: A mixture of primary calcium phosphate and gypsum**.