(a) (i) Deep sea divers depends upon compressed air for breathing at high pressure under water. The compressed air contains N₂ in addition to O₂ which are not very soluble in blood at normal pressure. However, at great depths when the diver breathes in compressed air from the supply tank, more N₂ dissolves in the blood and other body fluids because the pressure at that depth is far greater than the surface atmospheric pressure. When the diver comes towards the surface, the pressure decreases, N₂ comes out of the body quickly forming bubbles in the blood stream. These bubbles restrict blood flow, affect the transmission of nerve impulses. The bubbles can- even burst the capillaries or block them and starve the tissues of O₂. This condition is called "the bends, which are painful and dangerous to life.
(ii) At high altitudes the partial pressure of O ₂ is less that! that at the ground level. This results in low concentration of oxygen in the blood and tissues of the people living at high altitudes or climbers. The low blood oxygen causes climbers to become weak and unable to think clearly known as anoxia.
(b) To increase the solubility of CO₂ in soft drinks, the soda water bottles are sealed under high pressure. When the bottle is opened at room temperature under normal atmosphere conditions, the pressure inside the bottle decreases to atmospheric pressure and excess CO₂ fizzes out.

At a given pressure the solubility of oxygen in water increases with decrease in temperature. Therefore, the concentration of oxygen in sea is more in cold water and thus presence of more oxygen at lower temperature makes the aquatic species more comfortable in cold water.

Higher the value of Henry's law constant, K_H . lower is the solubility of gas in the liquid.

Molarity of a solution is defined as the number of moles of solute dissolved per litre of solution. Since volume depends on temperature and changes with change in temperature, therefore, the molarity will also change with change in temperature. On the other hand, mass does not change with change in temperature, and therefore, concentration terms such as mass percentage, mole fraction and molality which do not involve volume are independent of temperature.

NaCI is a non - volatile solute. On adding NaCI to water, vapour pressure is lowered and hence boiling point of water increases. Methyl alcohol is more volatile than water. On adding methyl alcohol into water, vapour pressure of solution is greater than that of water. Hence, boiling point of water decreases.