Final answer:
The relationship between the solubility of a gas and pressure is described by Henry's Law; solubility increases with increasing pressure and decreases with decreasing pressure due to changes in dynamic equilibrium and gas molecule concentration.
Step-by-step explanation:
The correct statement explaining the relationship between the solubility of a gas and its pressure is: (a) Solubility increases with increasing pressure and decreases with decreasing pressure. This concept is explained by Henry's Law, which states that the solubility of gases increases as the partial pressure of the gas above the solution increases. When the pressure of a gas is increased, more gas molecules will collide with the surface of a liquid and dissolve into it, leading to an increase in solubility. Conversely, when the pressure decreases, fewer gas molecules are in contact with the liquid, leading to a decrease in solubility.
When a gas is in contact with a liquid, a dynamic equilibrium is established between the dissolved gas molecules and the molecules in the gas phase above the solution. Increasing pressure raises molecule concentration in the gas phase, consequently increasing the concentration of dissolved gas molecules at equilibrium. The solubility of a gas in a liquid therefore is directly related to the pressure of the gas above the liquid.
For example, when a soda can is opened, the pressure above the liquid decreases, reducing the solubility of carbon dioxide and causing the gas to bubble out of the soda, as illustrated in Fig 5.2.6. Similarly, when the pressure is increased, more carbon dioxide would dissolve in the soda, which is why carbonated beverages are bottled under high pressure.