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Question #44530

Difficulty: 8/10 | 🟢 Free

The Question

A 34.2 g34.2 \text{ g} sample of sucrose (\ceC12H22O11\ce{C12H22O11}) is dissolved in 100.0 g100.0 \text{ g} of water. A trace amount of an acid catalyst is added, and the solution is heated until the inversion of sucrose is complete. The resulting monosaccharides undergo mutarotation and reach their respective anomeric equilibria. For D-glucose, the equilibrium mixture contains 36%36\% α\alpha-anomer and 64%64\% β\beta-anomer. For D-fructose, the equilibrium mixture contains 70%70\% β\beta-pyranose, 20%20\% β\beta-furanose, and 10%10\% α\alpha-furanose. Assuming the trace acid contributes negligibly to the molality, what is the boiling point elevation (ΔTb\Delta T_b) of the final solution? (KbK_b for water = 0.52 K kg mol−10.52 \text{ K kg mol}^{-1}, Molar mass of sucrose = 342 g mol−1342 \text{ g mol}^{-1}, Molar mass of water = 18 g mol−118 \text{ g mol}^{-1})

Options

  • A.

    1.06 K1.06 \text{ K}

  • B.

    1.04 K1.04 \text{ K}

  • C.

    1.56 K1.56 \text{ K}

  • D.

    2.65 K2.65 \text{ K}

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Boiling Point Elevation (Solvent vs Solution)|Van’t Hoff Factor (i) Application|D-Glucose Anomeric Equilibrium

Why This Question Is Tricky

Common Mistakes

The problem tests two major hidden traps.

First, the 'Chemical Exception' of mutarotation: students often incorrectly assume that anomeric equilibrium implies dissociation or creation of new particles, leading to an erroneous Van't Hoff factor (i>1i > 1).

In reality, isomerization does not change the total moles of solute.

Second, the 'Hidden Variable' of solvent consumption: during the hydrolysis (inversion) of sucrose, water acts as a reactant.

Failing to subtract the mass of consumed water (1.8 g1.8 \text{ g}) from the solvent mass leads to the incorrect molality and the trap answer of 1.04 K1.04 \text{ K}.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterSolutions - Class 12
ConceptBoiling Point Elevation (Solvent vs Solution)
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree