Question

Molality of aqueous solution of urea is 4.44 m. Then mole fraction of urea is x × 10^–3, then value of x is ____ 

Answer 1

Correct answer is: 74

\(\frac{X_B}{X_A}=\frac{m \times M_A}{1000}\)

Where m = molality

M_A = molar mass of solvent

\(\frac{X_B}{1-X_B}=\frac{4.44\times18}{1000}\) 

\(\frac{X_B}{1-X_B}=0.08\) 

X_B = 0.08 – 0.08X_B 

1.08 × B = 0.08 

X_B = 0.074 = 74 × 10^–3 

x = 74