Which of the following statements is true about the solubility of O_2 (g) in H_2O (l)?

• A. O_2 is highly soluble in water at room temperature.
• B. The solubility of O_2 in water increases as temperature decreases.
• C. The solubility of O_2 in water is unaffected by pressure.
• D. O_2 is insoluble in water under all conditions.

Answer: (B)

Verified step by step guidance

1. Understand that the solubility of gases in liquids generally depends on temperature and pressure, following Henry's Law and the effect of temperature on gas solubility.
2. Recall Henry's Law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid: \(S = k_H \times P\), where \(S\) is solubility, \(k_H\) is Henry's law constant, and \(P\) is the partial pressure of the gas.
3. Recognize that as temperature increases, the kinetic energy of gas molecules increases, making them less likely to stay dissolved in the liquid, so gas solubility typically decreases with increasing temperature.
4. Apply this knowledge to oxygen (\(O_2\)) in water: its solubility decreases as temperature increases and increases as temperature decreases.
5. Note that pressure affects gas solubility (higher pressure increases solubility), so the statement that solubility is unaffected by pressure is false, and oxygen is not insoluble in water under all conditions, so that statement is also false.