Three beakers labelled as A, B, and C each containing 25 mL of water were taken. A small amount of NaOH, and. CuSO4 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 the case of beaker C, the temperature of the solution falls. Which one of the following statements is/are correct?- In beakers A and B, an exothermic process has occurred.
- In beakers A and B, an endothermic process has occurred.
- In beaker C, the exothermic process has occurred.
- In beaker C, an endothermic process has occurred.
- Only I
- Only II
- I and IV
- II and III
Correct answer: (c) (i) and (iv)
Explanation: The reaction taking place in beaker A:
$NaOH + H_2O → Na^+ + OH^− + H_2O + heat $
The reaction taking place in beaker B:
$CuSO_4(s) + 5H_2O(l) → CuSO_4.5H_2O(s) + heat$
Therefore, both A and B are exothermic reactions that 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.
$NaCl + H_2O + heat→Na^+ + Cl^− + H_2O$
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