P is produced by the action of chlorine on dry slaked lime .
Q is a non -corrosive base and used for faster cooking .
On heating R at 373 K , it becomes calcium sulphate hemihydrate .
Identify P , Q and R respectively .

Options

A. `CaOCl_(2) , NaHCO_(3),` gypsum
B. `CaO,Na_(2)CO_(3),CaOCl_(2)`
C. `Ca(OH)_(2),NaHCO_(3),CaSO_(4)`
D. `CaOCl_(2),Na_(2)CO_(3),NH_(4)Cl`

Explanation

To solve the problem, we need to identify the substances P, Q, and R based on the given clues.

### Step-by-Step Solution:

1. **Identifying P:**
- The question states that P is produced by the action of chlorine on dry slaked lime.
- Dry slaked lime is chemically represented as \( \text{Ca(OH)}_2 \).
- When chlorine gas (\( \text{Cl}_2 \)) reacts with dry slaked lime, the reaction produces bleaching powder, which is \( \text{Ca(OCl)}_2 \).
- Therefore, we can conclude that:
- **P = Bleaching Powder (Ca(OCl)2)**

2. **Identifying Q:**
- The question mentions that Q is a non-corrosive base used for faster cooking.
- The common non-corrosive base used in cooking is baking soda, which is chemically represented as \( \text{NaHCO}_3 \).
- Therefore, we can conclude that:
- **Q = Baking Soda (NaHCO3)**

3. **Identifying R:**
- The question states that on heating R at 373 K, it becomes calcium sulfate hemihydrate.
- Calcium sulfate in its dihydrate form is known as gypsum, which is represented as \( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \).
- When gypsum is heated, it loses water and forms calcium sulfate hemihydrate, which is represented as \( \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \).
- Therefore, we can conclude that:
- **R = Gypsum (CaSO4·2H2O)**

### Final Identification:
- **P = Bleaching Powder (Ca(OCl)2)**
- **Q = Baking Soda (NaHCO3)**
- **R = Gypsum (CaSO4·2H2O)**

### Summary:
Thus, the final answers are:
- P: Bleaching Powder (Ca(OCl)2)
- Q: Baking Soda (NaHCO3)
- R: Gypsum (CaSO4·2H2O)