Question

How solubility of a gas in a liquid varies with i) Temperature ii) pressure?

Answer 1

Hint: The solubility of a gas in a liquid is directly proportional to the pressure of that gas and the solubility of a gas in a liquid is inversely proportional to the temperature.

Complete answer:In this question we have asked the relationship between the solubility of a gas in a liquid with temperature and pressure change. First, we will talk about temperature, how the solubility of gas changes with temperature. As we already mentioned that gas solubility in liquids is inversely proportional to temperature, which means solubility of the gas decreases with an increase in temperature. This happens because when we increase the temperature of a solution the particles dissolve in it either the molecules of water or any gas dissolved in it get energy from this heat and we know very well that particles are continuously moving. So, when we heat the solution, these particles have enough energy that they can escape the solution. This is the same process by which liquid turns into liquid. Now, the gas particles have more energy due to heat so they will leave the solution and will not dissolve in it.
Now come to the pressure relation with gas solubility. As we already mentioned that gas solubility is directly proportional to the pressure of the gas on the surface of the solution. For the understanding of this concept, we'll assume a solution in a close container with some gas dissolved in it. Some gas is present inside the solution and some gas is present at the surface of the solution and some gas particles are present above the solution. When we increase pressure on the solution, the particles of gas present above the solution will come close to the solution or at the surface of the solution. When these particles are present at such low distance to the water surface, the tendency of the particles to go and dissolve in the solution will increase. That's why we say pressure is directly proportional to the solubility of the gas in a liquid.

Note:
 We can also understand these both relations with Le Chatelier’s Principle which says that when the equilibrium of a system is disturbed, the system readjusts itself in such a way that the effect that has caused the change in equilibrium is countered.