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Question #44138

Difficulty: 8/10 | 🟢 Free

The Question

The standard reduction potentials E∘(\ceM2+/M)E^\circ(\ce{M^{2+}/M}) for \ce{Mn} and \ce{Zn} at 298 K298\text{ K} are −1.18 V-1.18\text{ V} and −0.76 V-0.76\text{ V}, respectively. The thermodynamic parameters for these metals are given below: Enthalpy of atomization (ΔaH∘\Delta_{a}H^\circ): \ce{Mn} = 281 kJ mol−1281\text{ kJ mol}^{-1}, \ce{Zn} = 130 kJ mol−1130\text{ kJ mol}^{-1}. Sum of first and second ionization enthalpies (IE1+IE2IE_1 + IE_2): \ce{Mn} = 2226 kJ mol−12226\text{ kJ mol}^{-1}, \ce{Zn} = 2639 kJ mol−12639\text{ kJ mol}^{-1}. Assuming that the standard entropy change (ΔS∘\Delta S^\circ) for the reduction half-reaction \ceM2+(aq)+2e−−>M(s)\ce{M^{2+}(aq) + 2e^- -> M(s)} is identical for both metals, calculate the difference in their standard hydration enthalpies, ΔhydH∘(\ceZn2+)−ΔhydH∘(\ceMn2+)\Delta_{hyd}H^\circ(\ce{Zn^{2+}}) - \Delta_{hyd}H^\circ(\ce{Mn^{2+}}). (Use F=96500 C mol−1F = 96500\text{ C mol}^{-1})

Options

  • A.

    −181 kJ mol−1-181\text{ kJ mol}^{-1}

  • B.

    −343 kJ mol−1-343\text{ kJ mol}^{-1}

  • C.

    +181 kJ mol−1+181\text{ kJ mol}^{-1}

  • D.

    −262 kJ mol−1-262\text{ kJ mol}^{-1}

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Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Exception_Exposure

Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.

Concepts Behind This Question

Electron Transfer Accounting|Electrode Potential Dependencies|E° (M²⁺/M) Anomalies

Why This Question Is Tricky

Common Mistakes

Students often incorrectly attribute the highly negative E∘(\ceMn2+/Mn)E^\circ(\ce{Mn^{2+}/Mn}) solely to the low ionization energy associated with its stable d5d^5 configuration.

This problem forces a rigorous 'Electron Transfer Accounting' via a full Born-Haber cycle.

The hidden complexity is that while the low (IE1+IE2)(IE_1 + IE_2) strongly favors \ce{Mn} oxidation, its higher atomization energy (compared to \ce{Zn}) and less negative hydration energy actually oppose it.

The trap lies in failing to correctly assign signs in the thermodynamic cycle for reduction or assuming a linear correlation between ionization energy and electrode potential without accounting for all three thermodynamic variables.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterRedox Reactions - Class 11 Part 2
ConceptElectron Transfer Accounting
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree