Which compound would you expect to be alkaline when dissolved in water?

Sodium hydroxide is expected to be alkaline when dissolved in water because it is a strong base. When it dissolves, it dissociates into sodium ions and hydroxide ions. The presence of hydroxide ions increases the pH of the solution, making it alkaline.

In contrast, sodium chloride is a neutral salt formed from the reaction of a strong acid and a strong base, and it does not affect the pH of the solution significantly when dissolved. Hydrochloric acid is a strong acid that would lower the pH of a solution, making it acidic rather than alkaline. Chlorine gas, being a non-metal gas, does not produce hydroxide ions in water and therefore does not contribute to an alkaline solution.