A molal solution of sodium chloride has a density of 1.21 g mL^–1. The molarity of this solution is:

1.143

The correct answer is option 2. 1.143.

We are given 1 molal solution \(⇒ \text{1 mole solute in 1kg solvent}\)

So, \(\text{1 mol NaCl = 58.5 g NaCl}\)

So, total mass of solution

Volume of solution \( = \frac{Mass}{Density}\)

                             \( = \frac{1058.5 g}{1.21 g / mL}\)

                             \( = 874.8 mL\)

Molarity (M) \(=\frac{\text{1 mole solute (n)}}{Volume of solute (V)}\)

                  \(= \frac{1 × 10^3}{874.8} = 1.143 M\)

\(⇒ 1 molal NaCl = 1.143 M\) of NaCl