Which of the following conditions will be helpful in liquification of gases ?

Correct option is C

The correct option for liquefaction of gases is : Decrease in temperature and increase in pressure.
Liquification of gases is achieved by subjecting the gas to conditions of low temperature and high pressure. This combination causes the gas particles to come closer together and lose energy, eventually leading to the formation of a liquid.
• Option (a) Increase in temperature and decrease in pressure is not helpful in liquefication. Raising the temperature generally makes gases less likely to liquefy, as the gas particles gain more kinetic energy and move further apart. Decreasing the pressure may allow the gas to expand and become less dense, making it even harder to liquefy.
• Option (b) Increase in both temperature and pressure is also not helpful for liquefication. Increasing the temperature, as explained earlier, makes gases less likely to liquefy. Raising the pressure alone might not be sufficient to cause liquefaction unless the temperature is lowered as well.
• Option (d) Decrease in both temperature and pressure is not effective for liquefication either. Lowering both temperature and pressure can lead to the formation of a solid or directly cause sublimation without going through a liquid phase.
In summary, for successful gas liquefaction, you need to decrease the temperature and increase the pressure, as stated in option (c).