Question

Assertion :When a salt such as $NaCl$ dissolves, the $N{a}^{+}$ and $C{l}^{-}$ ions leaving the crystal lattice acquire far greater freedom. Reason: In thermodynamic 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. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

In $NaCl$ crystal $N{a}^{+}$ and $C{l}^{-}$ are strongly bonded due to electrostatic attraction.

As it is dissolved in solvent, $N{a}^{+}$ and $C{l}^{-}$ 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 correct but reason is incorrect.