Question

The reaction between water and quick lime gives rise to Calcium hydroxide. Which of the following statements are correct?

I. The reaction is exothermic.

II. The pH of the final solution is less than 7.

III. The reaction is endothermic.

IV. The pH of the final solution is greater than 7.

• A. I and II
• B. I and III
• C. I and IV
• D. II and III

Answer 1

The correct option is C

I and IV

Explanation for correct option

Option C) I: The chemical reaction which involves the release of heat to the surroundings is called an exothermic reaction. A combustion reaction is an example of an exothermic reaction.

III. The reaction between water and quick lime $\left(\mathrm{CaO}\right)$ is,

$$\begin{gathered} \mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+\mathrm{heat} \\ (\mathrm{Calcium})\left(\mathrm{Water}\right)(\mathrm{Calcium} \\ \mathrm{oxide})\mathrm{hydoxide}) \end{gathered}$$

The product calcium hydroxide is basic in nature. So, the pH is less than 7.

Explanation for incorrect options

Option A) The pH of the final solution is greater than seven due to the formation of calcium hydroxide basic solution.

Option B) The reaction is exothermic.

Option D) The pH of the final solution is greater than seven due to the formation of calcium hydroxide basic solution.

Hence option (C) is correct., the reaction is exothermic and the pH of the final solution is greater than 7.