Q47 / 180 · AIIMS 2007 · Chemistry

Assertion : As a salt such as \(\mathrm{NaCl}\) dissolves, the \(\mathrm{Na}^{+}\)and \(\mathrm{Cl}^{-}\)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 true and reason is the correct explanation of assertion.
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
  • Correct answer
    C
    If assertion is true but reason is false.
  • D
    If both assertion and reason are false.

Solution

In thermodynamic terms, formation of solution occurs with a favourable change in free energy \(\Delta G=\Delta H-T \Delta S\) where \(\Delta H\) has a small positive value and \(T \Delta S\) a large positive value; thus \(\Delta G\) is negative.

Hence, the correct answer is option: 'C'.

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