Question

Three beakers labelled as A, B and C each containing $25\mathrm{mL}$ of water were taken. A small amount of $\mathrm{NaOH}$, anhydrous${\mathrm{CuSO}}_4$ and were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas, in the case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct? $\left(\mathrm{i}\right)$ In beakers A and B, the exothermic process has occurred.

$\left(\mathrm{ii}\right)$ In beakers A and B, the endothermic process has occurred.

$\left(\mathrm{iii}\right)$ In beaker C exothermic process has occurred.

$\left(\mathrm{iv}\right)$ In beaker C endothermic process has occurred.

• A. $\left(\mathrm{i}\right)\mathrm{only}$
• B. $\left(\mathrm{ii}\right)\mathrm{only}$
• C. $\left(\mathrm{i}\right)\mathrm{and}\left(\mathrm{iv}\right)$
• D. $\left(\mathrm{ii}\right)\mathrm{and}\left(\mathrm{iii}\right)$

Answer 1

The correct option is C

$\left(\mathrm{i}\right)\mathrm{and}\left(\mathrm{iv}\right)$

Explanation for Correct option:

(C) $\left(\mathrm{i}\right)\mathrm{and}\left(\mathrm{iv}\right)$

• The temperature will rise during exothermic processes whereas it will fall during endothermic ones.
• The chemical reaction in beakers A and B generates heat. The solution's temperature rises as a result. It falls within the exothermic process category.
• However, the temperature falls as a result of heat being absorbed by the water in the beaker C. We can categorize it as an endothermic process as a result. Hence, (i) and (iv) is the correct answer.

Explanation for incorrect options:

(A) $\left(\mathrm{i}\right)\mathrm{only}$

• This is the correct statement but this option does not tell about the beaker C reaction.
• So, this is an incorrect option.

(B) $\left(\mathrm{ii}\right)\mathrm{only}$

• The reaction that occurs in beakers A & B is exothermic, which is the absorption of heat.
• But here, it is given incorrectly as endothermic.
• So this is an incorrect option.

(D) $\left(\mathrm{ii}\right)\mathrm{and}\left(\mathrm{iii}\right)$

• The reaction that occurs in beakers A & B is exothermic, and in beakers, C is an endothermic reaction.
• But here, it is given incorrectly in the statement, this is an incorrect option.

Hence, the correct option is (C) $\left(\mathrm{i}\right)\mathrm{and}\left(\mathrm{iv}\right)$