Question:

31 g of ethylene glycol (C$_2$H$_6$O$_2$) is mixed with 500 g of solvent ($K_f = 2$ K kg mol$^{-1}$). What is the freezing point of the solution in K? (Freezing point of solvent = 273 K)

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Non-electrolytes: van’t Hoff factor = 1.
Updated On: May 2, 2026
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The Correct Option is B

Solution and Explanation

Concept: Freezing point depression
\[ \Delta T_f = K_f \times m \] ---

Step 1: Molar mass

\[ C_2H_6O_2 = 2(12) + 6(1) + 2(16) = 62 \] ---

Step 2: Moles

\[ \frac{31}{62} = 0.5 \text{ mol} \] ---

Step 3: Molality

\[ m = \frac{0.5}{0.5} = 1 \] ---

Step 4: Depression

\[ \Delta T_f = 2 \times 1 = 2 \text{ K} \] ---

Step 5: Final freezing point

\[ 273 - 2 = 271 \text{ K} \] --- Final Answer: \[ \boxed{271 \text{ K}} \]
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