Question

3.0 g of acetic acid is dissolved in 80 g of benzene. The molality of the solution is

Hint:

Molality is the ratio of the moles of solute to the mass of the solvent in kilograms.

Answer 1

Step 1: Formula for molality.
The molality \( m \) is given by: \[ m = \frac{\text{moles of solute}}{\text{mass of solvent (kg)}} \] Step 2: Calculate moles of acetic acid.
Moles of acetic acid = \( \frac{\text{mass of solute}}{\text{molar mass of acetic acid}} = \frac{3.0 \, \text{g}}{60 \, \text{g/mol}} = 0.05 \, \text{mol} \) Step 3: Calculate molality.
Mass of benzene = 80 g = 0.080 kg Molality = \( \frac{0.05 \, \text{mol}}{0.080 \, \text{kg}} = 0.00625 \, \text{mol/kg} \) Step 4: Conclusion.
Hence, the correct answer is (B) 0.00625 mol kg$^{-1}$.