A molal solution of sodium chloride has a density of 1.21 g mL–1. The molarity of this solution is:
Answer & explanation
Correct answer: option 2
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
| \(= 58.5 g \) | \(+ 1000g\) | \(= 1058.5 g\) |
| (Solute) | (solvent) | (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