Density of 3 M NaCl solution is 1.25 text g/mL . The molality of the solution is:

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EEJ MAIN Chemistry QUESTION #1003

Question 1

Density of 3 M NaCl solution is \(1.25\ \text{g/mL}\). The molality of the solution is:

1.79 m
2.79 m✔️
2 m
3 m

Correct Answer Explanation

Molar mass of NaCl \(= 58.5\ \text{g/mol}\). Mass of solute in 1 L: \(3 \times 58.5 = 175.5\ \text{g}\). Mass of solution \(= 1000 \times 1.25 = 1250\ \text{g}\). Mass of solvent \(= 1250 - 175.5 = 1074.5\ \text{g} = 1.0745\ \text{kg}\). Molality \(= \frac{3}{1.0745} \approx 2.79\ \text{m}\).

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