Which of the following statement is true about vapor pressure of a liquid?a)Vapor pressure is closely related to molecular activity and temperature of the liquidb)Vapor pressure is closely related to molecular activity but independent of the temperature of the liquidc)Vapor pressure is not affected by molecular activity and temperature of the liquidd)Vapor pressure is not affected by molecular activity and is independent of the temperature of the liquidCorrect answer is option 'A'. Can you explain this answer?

Question

Answer

Vapor pressure is closely related to molecular activity and temperature of the liquid.

Molecular activity refers to the movement and interactions of molecules within a substance. In a liquid, molecules are in constant motion, colliding with each other and the container walls. Some of these molecules have enough kinetic energy to escape from the liquid phase and enter the gas phase. The pressure exerted by the vapor molecules in equilibrium with the liquid is known as the vapor pressure.

1. Molecular Activity and Vapor Pressure:
The vapor pressure of a liquid is directly proportional to the molecular activity. As the molecular activity increases, more molecules have enough energy to escape from the liquid and enter the gas phase. This leads to an increase in the number of vapor molecules above the liquid surface, resulting in a higher vapor pressure. Conversely, when the molecular activity decreases, fewer molecules escape from the liquid, leading to a lower vapor pressure.

2. Temperature and Vapor Pressure:
Temperature also plays a crucial role in determining the vapor pressure of a liquid. At higher temperatures, the average kinetic energy of the molecules increases. This means that more molecules have enough energy to overcome the intermolecular forces holding them in the liquid phase, leading to a higher vapor pressure. On the other hand, at lower temperatures, the average kinetic energy decreases, resulting in fewer molecules escaping from the liquid, and consequently, a lower vapor pressure.

3. Relationship between Molecular Activity, Temperature, and Vapor Pressure:
The relationship between molecular activity, temperature, and vapor pressure can be summarized as follows:

- As the molecular activity increases, the vapor pressure of the liquid increases.
- As the temperature increases, the vapor pressure of the liquid increases.
- The vapor pressure is directly proportional to both molecular activity and temperature.

In conclusion, the true statement is that vapor pressure is closely related to molecular activity and temperature of the liquid.

Answer

The vapor pressure of a liquid at a given temperature is given by the pressure ex-erted by the saturated vapor on the liquid surface. When the vapor is saturated, an equilibrium exists between the liquid and the vapor phases. The number of molecules leaving the liquid surface is equal to the number of molecules entering the liquid surface. Hence, it is obvious that vapor pressure will be related to molecular activity and consequently to temperature. With the increase in temperature molecular activity increases as a result of which vapor pressure increases.

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