Vapour pressure of a liquid decreases with

Options

A. decrease in temperature
B. increase in temperature
C. increase in surface area
D. increase in volume .

Answer

To solve the question regarding the factors affecting the vapor pressure of a liquid, let's analyze each of the given options step by step.

### Step 1: Understanding Vapor Pressure
Vapor pressure is defined as the pressure exerted by the vapor of a substance when it is in equilibrium with its liquid or solid phase. This means that vapor pressure is a measure of the tendency of a substance to evaporate.

**Hint:** Remember that vapor pressure is related to the equilibrium between the liquid and its vapor.

### Step 2: Analyzing the Effect of Temperature
Vapor pressure is directly proportional to temperature. When the temperature of a liquid increases, the kinetic energy of its molecules also increases. This leads to an increase in the rate of evaporation, resulting in more vapor being present above the liquid, which increases the vapor pressure.

**Hint:** Think about how heating a liquid affects the movement of its molecules.

### Step 3: Analyzing the Effect of Surface Area
Vapor pressure is also directly proportional to the surface area of the liquid. A larger surface area allows more molecules to escape into the vapor phase, which increases the vapor pressure.

**Hint:** Consider how the exposure of a liquid to air influences evaporation.

### Step 4: Analyzing the Effect of Volume
Vapor pressure is directly proportional to the volume of the container holding the liquid. A larger volume means more space for molecules to evaporate, which can lead to an increase in vapor pressure.

**Hint:** Visualize how a larger container might allow more molecules to escape into the vapor phase.

### Step 5: Evaluating the Options
Now, let’s evaluate the options provided in the question:
1. **Decrease in Temperature**: As discussed, if the temperature decreases, the vapor pressure decreases.
2. **Increase in Temperature**: This would increase vapor pressure.
3. **Increase in Surface Area**: This would also increase vapor pressure.
4. **Increase in Volume**: This would increase vapor pressure as well.

From the analysis, the only correct statement is that vapor pressure decreases with a decrease in temperature.

### Conclusion
The correct answer is that the vapor pressure of a liquid decreases with a decrease in temperature.

**Final Answer:** The vapor pressure of a liquid decreases with a decrease in temperature.