Question 9 - MCQs from NCERT Exemplar - Chapter 1 Class 10 - Chemical Reactions and Equations

Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?

(i) It is an endothermic reaction

(ii) It is an exothermic reaction

(iii) The pH of the resulting solution will be more than seven

(iv) The pH of the resulting solution will be less than seven

(A) (i) and (ii) 

(B) (ii) and (iii)

(C) (i) and (iv) 

(D) (iii) and (iv)

Answer

Here,

• Since heat is liberated in the reaction, it is an exothermic reaction .
• The end product formed is Ca(OH) ₂ i.e calcium hydroxide. It is a base , so the pH of the resulting solution will be more than 7.

So, the correct answer is (b) - (ii) and (iii)