In liquid ammonia, NH4Cl behaves as an acid and NaNH2 as a base. What mass of NaNH2 is needed to neutralise 5.35 g of NH4Cl in liquid ammonia? (H = 1, N = 14, Na = 23, Cl = 35.5)

JEE Advanced levelSingle correct optionDifficulty 3 of 3sb027

In liquid ammonia, $NH X_{4} Cl$ behaves as an acid and $NaNH X_{2}$ as a base. What mass of $NaNH X_{2}$ is needed to neutralise $5.35 g$ of $NH X_{4} Cl$ in liquid ammonia? (H = 1, N = 14, Na = 23, Cl = 35.5)

Liquid ammonia autoionises as

2 NH X_{3} NH X_{4} X^{+} + NH X_{2} X^{-}

, so

NH X_{4} X^{+}

is the acid and

NH X_{2} X^{-}

the base.

NH X_{4} Cl + NaNH X_{2} NaCl + 2 NH X_{3}

is 1:1. Moles of

NH X_{4} Cl

5.35/53.5 = 0.100

, and the mass of

NaNH X_{2}

(molar mass 39) is

0.100 \times 39 = 3.90 g