Which action increases the concentration of gas dissolved in a liquid?

• A. Cooling the solution
• B. Heating the solution
• C. Increasing the volume of the solution
• D. Decreasing the volume of the solution

Answer: (A)

Gas solubility in liquids is greatly affected by temperature. For most gases, the dissolution process releases heat, so heating the liquid tends to push gas back into the gas phase and lowers the amount dissolved. Cooling, on the other hand, reduces molecular energy and makes it easier for gas molecules to stay dissolved, increasing their concentration in the liquid. Volume changes don’t directly increase the amount dissolved at a given temperature and pressure—they mainly change concentration by diluting or concentrating the dissolved gas, which isn’t the same as increasing the solubility. So cooling the solution increases the concentration of dissolved gas.