Question

Calculate molality of the solution containing nonvolatile solute if boiling point elevation of the solution is 0.2 K

\[ \left[\mathrm{K}_{\mathrm{b}}=0.52 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right] \]

• A. \(0.162\text{ }\mathrm{mol}\text{ }\mathrm{kg}^{-1}\)
• B. \(0.281\text{ }\mathrm{mol}\text{ }\mathrm{kg}^{-1}\)
• C. \(0.385\text{ }\mathrm{mol}\text{ }\mathrm{kg}^{-1}\)
• D. \(0.501\text{ }\mathrm{mol}\text{ }\mathrm{kg}^{-1}\)

Hint:

Use \(\Delta T_b=K_b\,m\) and solve for molality.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
Elevation in boiling point is directly proportional to molality: \(\Delta T_b=K_b\,m\).

Step 2: Given Data
\(\Delta T_b=0.2\text{ K}\), \(K_b=0.52\text{ K kg mol}^{-1}\).

Step 3: Calculation
\(m=\dfrac{\Delta T_b}{K_b}=\dfrac{0.2}{0.52}=0.385\text{ mol kg}^{-1}\)

Final Answer:
The molality of the solution is 0.385 mol per kg. \[ \boxed{\text{(C) }0.385\text{ mol kg}^{-1}} \]