Justify the following statements with an explanation:

i) Solubility of calcium oxide decreases with increase in temperature.

ii) What happens to the solubility in exothermic process with regard to temperature?

iii) In endothermic process, solubility increases with increase in temperature.

iv) At a given temperature, increase in pressure increases the solubility of the gas.

i) Addition of calcium oxide (CaO) to water is an exothermic process. For exothermic processes, solubility decreases with increase in temperature and that is why solubility of calcium oxide decreases with increase in temperature.

ii) In exothermic process, the solubility decreases with the increase in temperature. This means that when you will heat the mixture then solute will become less soluble. For example, amount of dissolved oxygen decreases in hot water.

iii) An endothermic process is a process in which we need to give heat to carry out the process i.e. heat is absorbed. For example addition of potassium nitrate (KNO₃) to water is an endothermic process. It means that we need to heat the mixture of KNO₃ and water to dissolve KNO₃ in water. This is so because on increasing the temperature the bonds of KNO₃ break more easily and thus it gets dissolved easily. In this way the solubility increases with increase in temperature.

iv) Solubility of a gas in a liquid increase with the increase in pressure. This can be justified with an example of solubility of CO₂ in soft drinks. Carbon dioxide is filled in soft drinks bottles at high pressure due to which it becomes highly soluble in the soft drink. When we open the bottle numerous times, the soft drink loses its taste because solubility decreases due to decrease in pressure.