Assertion : When a salt such as NaCl dissolves, the Na^+ and Cl^-…

MCQ

Assertion : When a salt such as $NaCl$ dissolves, the $Na^+$ and $Cl^-$ ions leaving the crystal lattice acquire far greater freedom.
Reason : In thermodyanamic terms, the formation of solution occurs with a favourable change in free energy, i.e., $\Delta H$ has a high positive value and $T\Delta S$ a low negative value.

A
If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
B
If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
✓
If the Assertion is correct but Reason is incorrect.
D
If both the Assertion and Reason are incorrect.

✓

Answer

Correct option: C.

If the Assertion is correct but Reason is incorrect.

c
In $NaCl$ crystal $Na^+$ and $Cl^-$ are strongly bonded due to electrostatic attraction. As it is dissolved in solvent, $Na^+$ and $Cl^-$ acquire greater freedom. In thermodynamic terms formation of solution occurs with a favourable change in $\Delta G$. $T\Delta S$ is largely $-ve$ which overcomes the small $+ve$ value of $\Delta H$. Thus $\Delta G$ is negative for dissolution of salt. Hence assertion is true but reason is false.

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