Which of the following condition is most favourable for converting gas into liquid?

Question

Accepted Answer

To convert a gas into a liquid, the conditions must favor the condensation of gas molecules. Option 1, which is high pressure and low temperature, is the most favorable condition for this process. Here's why:

1. **High Pressure**: Increasing the pressure on a gas forces the molecules closer together. When gas molecules are compressed, they are more likely to interact with each other. These interactions can lead to the formation of intermolecular forces, which are necessary for the transition from the gaseous to the liquid state. High pressure effectively reduces the volume available for the gas molecules, increasing the likelihood of condensation.

2. **Low Temperature**: Lowering the temperature of a gas decreases the kinetic energy of its molecules. With reduced kinetic energy, the molecules move more slowly and are less able to overcome the attractive forces between them. This makes it easier for the gas molecules to come together and form a liquid. Low temperature is crucial because it reduces the thermal energy that keeps the molecules apart in the gaseous state.

Now, let's examine why the other options are incorrect:

- **Option 2 (Low pressure, low temperature)**: While low temperature is favorable for liquefaction, low pressure is not. Low pressure allows gas molecules to spread out and reduces the likelihood of intermolecular interactions necessary for condensation. Therefore, low pressure counteracts the effect of low temperature, making this option less favorable.

- **Option 3 (Low pressure, high temperature)**: Both low pressure and high temperature are unfavorable for converting gas into liquid. Low pressure, as mentioned, allows molecules to remain far apart, while high temperature increases the kinetic energy of the molecules, making them move faster and resist condensation. This combination is the least favorable for liquefaction.

- **Option 4 (High pressure, high temperature)**: Although high pressure is favorable for liquefaction, high temperature is not. High temperature increases the kinetic energy of the gas molecules, which can overcome the attractive forces that would otherwise bring them together to form a liquid. Thus, the effect of high temperature negates the benefit of high pressure in this context.

In summary, Option 1 (high pressure, low temperature) is the most favorable condition for converting gas into liquid because it maximizes the intermolecular interactions necessary for condensation while minimizing the kinetic energy that keeps the molecules apart.