The question asks for the normal boiling point of water at a specific pressure. The normal boiling point is defined as the temperature at which a liquid boils at standard atmospheric pressure. We need to recall the standard values for water's boiling point in different temperature scales.
Correct Option: C) 100°C is the standard and widely known normal boiling point of water at 1.013 bar (standard atmospheric pressure).
The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure. We need to understand how atmospheric pressure changes with altitude and how this affects the boiling point of water.
Correct Option: C) Decreases. At higher altitudes, atmospheric pressure is lower. For water to boil, its vapor pressure must equal the atmospheric pressure. With lower external pressure, water needs less energy (lower temperature) to reach this point, hence its boiling point decreases.
The question asks about the phases involved in sublimation equilibrium. To answer this, we need to recall the definition of sublimation and the concept of equilibrium in phase transitions.
Correct Option: A) A solid and its vapour
This option correctly identifies the two phases involved in sublimation equilibrium. The direct transition between solid and gas (vapour) is characteristic of sublimation, and equilibrium implies a balance between these two phases.
The question asks about Henry's law, which describes the solubility of gases in liquids. We need to identify the factor to which the mass of dissolved gas is directly proportional according to this law.
Correct Option: C) The pressure of the gas above the solvent
Henry's law explicitly states that the mass (or amount) of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the surface of the liquid. Increasing the pressure of the gas above the solvent forces more gas molecules into the solution to maintain equilibrium.
The question asks why soda water fizzes when the bottle is opened. This phenomenon is directly related to the solubility of gases in liquids and how it changes with pressure. We need to understand the principles governing gas solubility to determine the correct explanation.
D) The pressure decreases, reducing CO₂ solubility, so dissolved CO₂ escapes. This option accurately describes the physical process that occurs when a soda bottle is opened, leading to fizzing. The decrease in pressure directly causes a decrease in the solubility of CO₂ in the water, forcing the dissolved gas to escape as bubbles.
The question asks about the general trend of gas solubility in a liquid with increasing temperature. This is a fundamental concept in chemistry, particularly related to physical chemistry and solutions.
D) Decreases — The dissolution of most gases in liquids is an exothermic process. According to Le Chatelier's Principle, increasing the temperature shifts the equilibrium towards the reactants (undissolved gas), thus decreasing the solubility of the gas in the liquid.