Question

For dissolution of $NaOH$ in water $\Delta S$ is

• A. +ve
• B. -ve
• C. zero
• D. none

Answer 1

The correct option is A +ve

Dissolution of $N{H}_{4}Cl$ in water:
There is a final solution, that is the water molecules pull apart the NaOH lattice as a result of dipole - dipole interactions of the charged ions in the lattice in a reaction called hydration - the $NaOH$ dissolves to yield $N{a}^{+}$ and $[OH{]}^{-}$ ions
$NaOH\left(s\right)\to N{a}^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$
here as no of ions in solution increases so entropy of system increases & $\Delta S$ is $+ve$.