Question

Molality (m) of 3 M aqueous solution of NaCl is: 

(Given : Density of solution = 1.25 g \(mL^{-1}\) , Molar mass in g \(mol ^{-1}\) : Na-23, Cl-35.5)

(1) 2.90 m 

(2) 2.79 m 

(3) 1.90 m

(4) 3.85 m

Answer 1

Correct option is (2) 2.79 m 

3 moles are present in 1 liters solution 

molality \(= \frac {3 \times 1000}{1.25 \times 1000-[3 \times 58.5]} = 2.79\, m\)