The correct option is **B. Pressure of the gas above the liquid**. ### Detailed Explanation: 1. **Understanding Gas Solubility**: - The solubility of a gas in a liquid refers to the amount of gas that can dissolve in a given volume of liquid at a specific temperature and pressure. This phenomenon is governed by several factors, but the most significant one is the pressure of the gas above the liquid. 2. **Henry's Law**: - The relationship between the solubility of a gas and the pressure of that gas is described by **Henry's Law**. Henry's Law states that at a constant temperature, the amount of gas that dissolves in a liquid is directly proportional to the partial pressure of that gas above the liquid. Mathematically, it can be expressed as: \[ C = k_H \cdot P \] where: - \( C \) is the concentration of the dissolved gas, - \( k_H \) is Henry's law constant (which varies with temperature and the nature of the gas and solvent), - \( P \) is the partial pressure of the gas above the liquid. 3. **Why Option B is Correct**: - According to Henry's Law, increasing the pressure of the gas above the liquid increases the solubility of the gas in the liquid. This is because more gas molecules are forced into the liquid phase when the pressure is increased, leading to a higher concentration of dissolved gas. ### Analysis of Other Options: - **Option A: Temperature of the gas**: - While temperature does affect the solubility of gases, it is not the primary factor. Generally, as temperature increases, the solubility of gases in liquids decreases. This is because higher temperatures provide gas molecules with more kinetic energy, allowing them to escape from the liquid more easily. However, the direct influence of pressure is more significant in determining solubility. - **Option C: Molecular weight of the gas**: - The molecular weight of a gas can influence its solubility to some extent, but it is not a primary factor. For example, heavier gases may have different solubility characteristics compared to lighter gases, but this is secondary to the effects of pressure and temperature. The solubility is more closely related to the interactions between the gas molecules and the solvent. - **Option D: Color of the liquid**: - The color of the liquid has no bearing on the solubility of a gas. Color is related to the absorption of light and does not influence the physical or chemical interactions that determine how much gas can dissolve in the liquid. ### Summary of Key Points: - The solubility of a gas in a liquid is primarily affected by the **pressure of the gas above the liquid** (Henry's Law). - Increasing pressure increases gas solubility, while increasing temperature generally decreases it. - Molecular weight and color of the liquid are not significant factors in determining gas solubility. ### Revision Summary: - **Primary Factor**: Pressure of the gas above the liquid (Henry's Law). - **Temperature**: Higher temperatures typically decrease gas solubility. - **Molecular Weight**: Affects solubility but is secondary to pressure. - **Color of Liquid**: Irrelevant to gas solubility.