Which of the following is an endothermic reaction?

Options

A. Formation of curd from milk
B. Production of gas when quicklime is added to water.
C. Opening of a soda bottle with production of gas
D. Evaporation of water

Answer

To determine which of the following is an endothermic reaction, we need to understand what an endothermic reaction is. An endothermic reaction is a chemical reaction that absorbs heat from its surroundings.

### Step-by-Step Solution:

1. **Understand Endothermic Reactions**:
- An endothermic reaction absorbs heat. This means that the temperature of the surroundings decreases as the reaction occurs.

2. **Evaluate the Options**:
- **Option 1: Formation of curd from milk**:
- When hot milk is added to the curd, it speeds up the formation of curd. This indicates that heat is absorbed from the milk, making this an endothermic reaction.
- **Option 2: Production of gas when quicklime is added to water**:
- When quicklime (CaO) is mixed with water (H2O), it forms slaked lime (Ca(OH)2) and releases heat. This is an exothermic reaction, not endothermic.
- **Option 3: Opening of a soda bottle with production of gas**:
- Opening a soda bottle releases gas, but this process does not absorb heat; it is also an exothermic reaction.
- **Option 4: Evaporation of water**:
- Evaporation requires heat energy to convert water into vapor. This process absorbs heat from the surroundings, making it an endothermic reaction.

3. **Identify the Correct Options**:
- From the evaluation, we find that:
- **Option 1 (Formation of curd from milk)** is an endothermic reaction.
- **Option 4 (Evaporation of water)** is also an endothermic reaction.

### Conclusion:
The correct answers are **Option 1** and **Option 4**.

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