Which of the following will increase the solubility of CO_2(g) in water?

• A. Adding NaCl to the water
• B. Decreasing the temperature of the water
• C. Decreasing the pressure of CO_2 above the water
• D. Increasing the temperature of the water

Answer: (B)

Verified step by step guidance

1. Understand that the solubility of gases in liquids is generally governed by Henry's Law, which states that the solubility of a gas is directly proportional to the partial pressure of that 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.
2. Recognize that temperature affects gas solubility because gas solubility typically decreases as temperature increases. This is due to the exothermic nature of gas dissolution; higher temperatures provide energy for gas molecules to escape from the liquid.
3. Consider the effect of adding NaCl (salt) to water, which usually decreases the solubility of gases due to the 'salting out' effect, where dissolved salts reduce the amount of gas that can dissolve.
4. Analyze the effect of pressure changes: decreasing the pressure of CO\(_2\) above the water will reduce its solubility according to Henry's Law, while increasing pressure would increase solubility.
5. Conclude that decreasing the temperature of the water increases the solubility of CO\(_2\) because lower temperatures favor gas dissolution, making this the correct choice among the options.