Question

Calculate \(\Delta T_b\) of a \(0.45\) m solution of a nonvolatile solute in solvent if molal elevation constant of solvent is \(3.0\) K kg mol\(^{-1}\)

• A. \(0.94\) K
• B. \(2.69\) K
• C. \(3.21\) K
• D. \(1.35\) K

Hint:

Delta Tb = Kb times m for a nonvolatile solute.

Answer 1

The Correct Option is D

Step 1: Idea:
Boiling point elevation is directly proportional to the molal concentration.

Step 2: Calculation:
$3 \times 0.45 = 3 \times 0.4 + 3 \times 0.05 = 1.2 + 0.15 = 1.35$ K.

Step 3: Check:
Since $K_b$ is 3 and molality is under 0.5, the result must be under 1.5 K, so 1.35 K is the only fitting option.

Final Answer:
$\Delta T_b = 1.35$ K, option (D). \[ \boxed{1.35 \text{ K}} \]