Which of the following best describes the effect of adding salt to water?

Adding salt to water primarily alters the boiling point, making this the best choice among the options provided. When salt (such as sodium chloride) is dissolved in water, it creates a solution that exhibits a phenomenon known as boiling point elevation. This occurs because the presence of dissolved ions from the salt disrupts the ability of water molecules to escape into the gas phase, thus requiring a higher temperature to reach the boiling point.

Adding salt to water does not decrease the solubility of salt in the solution; in fact, it can lead to a saturated solution if enough salt is added, which would not align with the first option. The freezing point of the solution is also lowered due to the same principles, known as freezing point depression, making the second option incorrect. Lastly, while adding salt can influence the pH if the salt is acidic or basic in nature, common table salt (sodium chloride) is neutral, and thus does not change the pH level significantly, rendering the fourth option inaccurate.

In summary, the impact of salt on the boiling point due to the elevation effect is the salient aspect of this interaction, highlighting the collisional effects of dissolved particles in a solvent.