Question

The molality of solution, when 18 g of glucose is added to 18 g of H2O is:

• A. 0.55 m
• B. 2.55 m
• C. 5.55 m
• D. 55.5 m

Hint:

Molality depends only on mass of solvent (in kg), not on total volume. Use it especially when temperature varies.

Answer 1

The Correct Option is C

Molality (m) = \(\frac{\text{moles of solute}}{\text{mass of solvent (kg)}}\)
Molar mass of glucose (C\textsubscript{6}H\textsubscript{12}O\textsubscript{6}) = 180 g/mol
Moles of glucose = \(\frac{18}{180} = 0.1\) mol
Mass of solvent = 18 g = 0.018 kg
\[ m = \frac{0.1}{0.018} = 5.55~\text{mol/kg} \]