A solution of sodium sulphate contains 92 g of $\mathrm{Na}^{+}$ ions per kilogram of water. The Molality of $\mathrm{Na}^{+}$ ions in that solution in $\mathrm{mol} \mathrm{kg}^{-1}$ is

JEE Main · 2019 · 09 Jan 2019 · Shift 1 · Some Basic Concepts of Chemistry

A solution of sodium sulphate contains 92 g of

Na^{+}

ions per kilogram of water. The Molality of

Na^{+}

ions in that solution in

mol kg^{- 1}

Answer: (B)

The sodium content is stated directly as

92 g

Na^{+}

per kilogram of water. With the molar mass of sodium

23 g mol^{- 1}

, the amount of

Na^{+}

\frac{92}{23} = 4 mol

, so the molality of

Na^{+}

4 mol kg^{- 1}

JEE Main · 2019 · 09 Jan 2019 · Shift 1 · Single correct option