Start Learning Free

Before You Begin

Question #44461

Difficulty: 8/10 | 🟢 Free

The Question

A 140 mmol140 \text{ mmol} sample of propane (\ceCH3−CH2−CH3\ce{CH3-CH2-CH3}) undergoes photochemical monochlorination at 298 K298 \text{ K}. The relative reactivity of 1∘1^{\circ} and 2∘2^{\circ} C-H bonds towards chlorine radicals is 1:41 : 4. The major monochlorinated product (A) is isolated based strictly on its theoretical kinetic yield. Compound (A) is then treated with \ceMg\ce{Mg} in dry ether, followed by bubbling \ceCO2(g)\ce{CO2(g)} and subsequent acidic workup (\ceH3O+\ce{H3O+}) to yield compound (B). The entire quantity of (B) produced is dissolved in 1.0 kg1.0 \text{ kg} of a non-polar solvent (dielectric constant ϵ≈2.2\epsilon \approx 2.2) having a cryoscopic constant Kf=5.0 K kg mol−1K_f = 5.0 \text{ K kg mol}^{-1}. Assuming (B) undergoes complete dimerization in this solvent due to intermolecular hydrogen bonding, what is the freezing point depression (ΔTf\Delta T_f) of the resulting solution?

Options

  • A.

    0.20 K

  • B.

    0.35 K

  • C.

    0.40 K

  • D.

    0.70 K

Check Your Answer

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

Free Radical Substitution Selectivity|Spontaneity Criteria|Van’t Hoff Factor (i) Application

Why This Question Is Tricky

Common Mistakes

This problem tests a student's ability to bridge organic kinetic control with physical chemistry non-ideality.

The first trap lies in the regioselectivity of free radical halogenation; students often assume either a 100% yield of the most stable radical product or a purely statistical distribution, ignoring the specific relative reactivity of C-H bonds.

The second trap is the Van't Hoff factor (i); students who blindly apply the colligative property formula will fail to account for the dimerization of carboxylic acids in low dielectric constant solvents, missing the i = 0.5 correction.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterHydrocarbons - Class 11 Part 2
ConceptFree Radical Substitution Selectivity
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree