Question

# Three beakers labelled as $$A,\ B$$ and $$C$$ each containing 25 mL of water were taken. A small amount of $$NaOH$$, anhydrous $$CuSO_4$$ and $$NaCl$$ 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 case of beaker $$C$$, the temperature of the solution falls. Which one of the following statement(s) is(are) correct ?(i) In beakers $$A$$ and $$B$$, exothermic process has occurred.(ii) In beakers $$A$$ and $$B$$, endothermic process has occurred.(iii) In beaker $$C$$ exothermic process has occurred.(iv) In beaker $$C$$ endothermic process has occurred.

A
(i) only
B
(ii) only
C
(i) and (iv)
D
(ii) and (iii)

Solution

## The correct option is C (i) and (iv)$$Concept:$$ When heat is released $$\text {(Exothermic process)}$$ surrounding gets warm means temperature rises. When heat is absorbed $$\text {(Endothermic process)}$$ surrounding gets cold means temperature falls.In beaker $$A$$:$$NaOH + H_{2}O \rightarrow Na^{+} + OH^{-} + H_{2}O + heat$$ In beaker $$B$$:$$CuSO_{4}(s) + 5H_{2}O(l) \rightarrow CuSO_{4}.5H_{2}O(s) + heat$$Therfore in both $$A$$ and $$B$$ exothermic reactions are taking place resulting in rise in temperature. On the other hand in beaker $$C$$, an endothermic reaction is taking place as heat is being absorbed, resulting in a decrease in temperature.$$NaCl + H_{2}O + heat \rightarrow Na^{+} + Cl^{- } + H_{2}O$$Chemistry

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