Q1: With increase in temperature, the solubility of gases in liquids, at fixed pressure

ANS:B - decreases

With an increase in temperature, the solubility of gases in liquids typically decreases. This phenomenon can be explained by Le Chatelier's principle, which states that when a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the equilibrium will shift to counteract the change. In the case of gases dissolved in liquids, increasing the temperature provides more energy to the system, which disrupts the intermolecular forces holding the gas molecules in solution. As a result, gas molecules are more likely to escape from the liquid phase into the gas phase, leading to a decrease in solubility. Therefore, in most cases, the solubility of gases in liquids decreases as temperature increases, making the correct option: decreases. The decrease in solubility of gases in liquids with increasing temperature can be explained by considering the effect of temperature on the intermolecular forces between gas molecules and solvent molecules.

1. Thermal Energy: As temperature increases, the thermal energy of molecules also increases. This increased thermal energy disrupts the intermolecular forces between gas molecules and solvent molecules.
2. Weakened Solvent-Solute Interactions: In a solution, gas molecules dissolve in the liquid solvent due to attractive forces between the gas molecules and the solvent molecules. These attractive forces can include London dispersion forces, dipole-dipole interactions, and hydrogen bonding. When the temperature increases, the increased thermal energy weakens these attractive forces, making it easier for gas molecules to overcome them and escape into the gas phase.
3. Henry's Law: Henry's Law describes the relationship between the solubility of a gas in a liquid and the pressure of the gas above the liquid. According to Henry's Law, at constant pressure, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. Therefore, when gas molecules escape from the liquid phase into the gas phase due to increased temperature, the equilibrium partial pressure of the gas above the liquid decreases. This, in turn, decreases the solubility of the gas in the liquid.
4. Le Chatelier's Principle: The decrease in solubility with increasing temperature can also be understood through Le Chatelier's Principle. When the system (the solution) at equilibrium is subjected to an increase in temperature, the equilibrium shifts in the direction that opposes the change. In this case, the system shifts to favor the formation of gas molecules in the gas phase, resulting in a decrease in the amount of gas dissolved in the liquid phase.