In a closed jar having water vapours in equilibrium with liquid suddenly all the vapours of the jar is transferred to another identical jar and is subjected to compression.Assume initial temperature to be the same and negligible volume occupied by the liquid water.Select the observation in the record jar.

Options

A. Liquid water will start forming in the jar
B. Vapour will undergo gradual compression without any condensation
C. Temperature of the vapour will increase
D. Final pressure will be the same as initial pressure

Explanation

To solve the problem, we need to analyze the situation step by step.

### Step-by-Step Solution:

1. **Understanding the Initial Condition**:
- We have a closed jar containing water vapor in equilibrium with liquid water. This means that the rate of evaporation of liquid water equals the rate of condensation of water vapor.

**Hint**: Remember that equilibrium implies a balance between two opposing processes.

2. **Transferring the Vapor**:
- All the water vapor is suddenly transferred to another identical closed jar. This jar also has negligible volume occupied by liquid water.

**Hint**: Consider how transferring vapor affects the equilibrium in the new jar.

3. **Compression of Vapor**:
- The vapor in the new jar is subjected to compression. Since the jar is closed, the volume available for the vapor decreases, which will lead to an increase in pressure.

**Hint**: Think about the gas laws and how pressure relates to volume and temperature.

4. **Condensation Process**:
- As the vapor is compressed, it will reach a point where it starts to condense into liquid water due to the increased pressure. This means that liquid water will start forming in the jar.

**Hint**: Recall that increasing pressure can lead to condensation if the temperature remains constant.

5. **Temperature Consideration**:
- The problem states that the initial temperature remains the same. Therefore, during the compression and condensation process, the temperature of the vapor does not increase.

**Hint**: Constant temperature implies that any energy change is related to phase change rather than temperature change.

6. **Final Pressure Comparison**:
- Since the new jar is identical in volume to the old jar, and assuming no gas is lost, we can apply the ideal gas law (P1V1 = P2V2). Given that V1 = V2, it follows that P1 = P2. Thus, the final pressure in the new jar will be the same as the initial pressure in the old jar.

**Hint**: Use the ideal gas law to relate pressure, volume, and temperature.

### Conclusion:
- From the analysis, we can conclude:
- **Observation A**: Liquid water will start forming in the jar (True).
- **Observation B**: Vapor will undergo gradual compression without any condensation (False).
- **Observation C**: Temperature of the vapor will increase (False).
- **Observation D**: Final pressure will be the same as the initial pressure (True).

### Final Answer:
The correct observations are A and D.