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JEE Advanced · Chemistry · 16. Solutions

When \(20 \mathrm{~g}\) of naphthoic acid \(\left(\mathrm{C}_{11} \mathrm{H}_8 \mathrm{O}_2\right)\) is dissolved in \(50 \mathrm{~g}\) of benzene \(\left(K_f=1.72 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)\), a freezing point depression of \(2 \mathrm{~K}\) is observed. The van't Hoff factor \((i)\) is

  1. A \(0.5\)
  2. B 1
  3. C 2
  4. D 3
Verified Solution

Answer & Solution

Correct Answer

(A) \(0.5\)

Step-by-step Solution

Detailed explanation

Actual molecular weight of napthoic acid \(\left(\mathrm{C}_{11} \mathrm{H}_8 \mathrm{O}_2\right)=172\)
\(\text {Molecular mass (calculated ) } =\frac{1000 . K_f \cdot w}{W . \Delta T_f} \)
\( =\frac{1000 \times 1.72 \times 20}{50 \times 2} \)
\( =344\)
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