When pellets of NaOH (s) are added to a flask of water, it is observed that the temperature of the water increases as the pellets dissolve. Which of the following claims about the observed dissolution of NaOH (s) in water is most accurate?

The given question is incomplete. The complete question is as follows.

When pellets of NaOH (s) are added to a flask of water, it is observed that the temperature of the water increases as the pellets dissolve. Which of the following claims about the observed dissolution of NaOH (s) in water is most accurate?

(a) an exothermic reaction

(b) an endothermic reaction

Explanation:

A reaction in which heat energy is absorbed by the molecules of a substance is known as an endothermic reaction.

Whereas when energy is released by the molecules of a substance in a reaction then it is known as an exothermic reaction.

When NaOH pallets are added to water then there occurs an increase in temperature of the solution. This means that heat energy is being released during this process.

Hence, the reaction will be exothermic in nature.

Thus, we can conclude that for the given reaction student can claim about the observed dissolution of NaOH (s) in water is most accurate as an exothermic reaction.