For a 0.10 M solution of sodium acetate at 298 K (K_a = 1.8x10^-5, h = sqrtK_h/c), the solution is diluted tenfold with pure water. Select the correct statements.

The degree of hydrolysis increases by a factor of sqrt10

The degree of hydrolysis can be decreased by adding a little solid NaOH, but not by adding solid CH3COONa

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ia018

For a 0.10 M solution of sodium acetate at 298 K ( $K_{a} = 1.8 \times 1 0^{- 5}$ , $h = K_{h} / c$ ), the solution is diluted tenfold with pure water. Select the correct statements.

AThe degree of hydrolysis increases by a factor of $10$
BThe pH decreases by 0.5 unit
C $K_{h}$ remains unchanged
DThe degree of hydrolysis can be decreased by adding a little solid NaOH, but not by adding solid $CH X_{3} COONa$

h \propto c^{- 1/2}

, so tenfold dilution raises

h

from 7.45e-05 to 2.36e-04, a factor of 3.162.

pH = 7 + \frac{1}{2} (p K_{a} + lo g c)

falls from 8.87 to 8.37.

K_{h} = K_{w} / K_{a}

depends only on temperature. D is wrong: adding more salt also lowers

h

(since

h \propto c^{- 1/2}

), so the 'but not' clause is false. Answer A, B, C.