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Question #44744

Difficulty: 8/10 | 🟢 Free

The Question

An aqueous solution of a weak monoprotic acid \ce{HA} (molar mass =120 g mol−1= 120 \text{ g mol}^{-1}) has a mass concentration of 0.048 g cm−30.048 \text{ g cm}^{-3} and a density of 1.088 g cm−31.088 \text{ g cm}^{-3} at 298 K298 \text{ K}. The electrolytic conductivity (κ\kappa) of the solution is 3.2×10−3 S cm−13.2 \times 10^{-3} \text{ S cm}^{-1}. Given the limiting molar conductivities Λm∘(\ceH+)=350 S cm2 mol−1\Lambda^\circ_m(\ce{H^+}) = 350 \text{ S cm}^2 \text{ mol}^{-1} and Λm∘(\ceA−)=50 S cm2 mol−1\Lambda^\circ_m(\ce{A^-}) = 50 \text{ S cm}^2 \text{ mol}^{-1}, calculate the boiling point of this solution at 1 atm1 \text{ atm}. (Assume KbK_b for water is 0.52 K kg mol−10.52 \text{ K kg mol}^{-1} and the boiling point of pure water is 373.150 K373.150 \text{ K}.)

Options

  • A.

    373.354 K

  • B.

    373.362 K

  • C.

    373.350 K

  • D.

    373.550 K

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Numerical_Precision

Improve calculation stamina and avoid rounding errors in high-stakes competitive examinations.

Concepts Behind This Question

Kohlrausch Law Infinite Dilution|Boiling Point Elevation (Solvent vs Solution)

Why This Question Is Tricky

Common Mistakes

The problem tests the integration of Electrochemistry (Kohlrausch's Law) and Colligative Properties.

The 'Hidden Variable' trap lies in the distinction between Molarity and Molality.

Students often directly use the calculated Molarity (0.4 M0.4 \text{ M}) in the boiling point elevation formula (yielding 373.362 K373.362 \text{ K}), neglecting the density correction required to find the true mass of the solvent.

Additionally, failing to compute the van't Hoff factor (ii) from the molar conductivity ratio leads to further deviations.

The unit conversion from mass concentration (g cm−3\text{g cm}^{-3}) to Molarity and then to Molality acts as a rigorous dimensional analysis filter.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterElectrochemistry - Class 12
ConceptKohlrausch Law Infinite Dilution
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree