Question

Solid Calcium oxide reacts vigorously with water to form Calcium hydroxide accompanied by the liberation of heat. From the information given above it may be concluded that this reaction

• A. is endothermic and pH of the solution formed is more than 7.
• B. is exothermic and pH of the solution formed is 7.
• C. is endothermic and pH of the solution formed is 7.
• D. is exothermic and pH of the solution formed is more than 7.

Answer 1

Answer: (D)

is exothermic and pH of the solution formed is more than 7.

Answer 2

The reaction between calcium oxide (quicklime) and water is highly exothermic and produces calcium hydroxide (a strong base), which increases the solution’s pH:
$\text{CaO (s)} + \text{H}_2\text{O (l)} \rightarrow \text{Ca(OH)}_2 \, + \, \text{heat}.$
As calcium hydroxide is a base, the pH of the solution is greater than 7.