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