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Question #44160

Difficulty: 8/10 | 🟢 Free

The Question

Consider the complete dissociation of 1 mole1\text{ mole} of \ce{O2(g)} into \ce{O(g)}. According to Molecular Orbital Theory (MOT), let xx be the number of unpaired electrons in an \ce{O2} molecule. Let yy be the number of unpaired electrons in an \ce{O} atom in its ground state.

A sample of 1 mole1\text{ mole} of \ce{O2(g)} initially at 300 K300\text{ K} and volume V0V_0 undergoes the following sequence of steps: Step 1: Reversible isothermal expansion to a volume V1V_1 such that the magnitude of work done is ∣W1∣=(y−x2)×3.486 kJ|W_1| = (y - \frac{x}{2}) \times 3.486\text{ kJ}. Step 2: Complete dissociation into \ce{O(g)} at constant volume V1V_1 and constant temperature 300 K300\text{ K}. Step 3: Reversible isothermal compression of the product gas back to the original volume V0V_0.

Given the standard enthalpy of dissociation of \ce{O2(g)} at 300 K300\text{ K} is ΔH∘=498.49 kJ/mol\Delta H^\circ = 498.49\text{ kJ/mol}. Assume ideal gas behavior for all species. (Use R=8.3 J K−1 mol−1R = 8.3\text{ J K}^{-1}\text{ mol}^{-1}, ln⁡2=0.7\ln 2 = 0.7)

Which of the following options correctly represents the net work done (WnetW_{net}) and the net heat absorbed (qnetq_{net}) by the system in the entire process? (Use standard IUPAC sign convention)

Options

  • A.

    Wnet=3.486 kJ,  qnet=492.514 kJW_{net} = 3.486\text{ kJ}, \; q_{net} = 492.514\text{ kJ}

  • B.

    Wnet=6.972 kJ,  qnet=489.028 kJW_{net} = 6.972\text{ kJ}, \; q_{net} = 489.028\text{ kJ}

  • C.

    Wnet=3.486 kJ,  qnet=495.004 kJW_{net} = 3.486\text{ kJ}, \; q_{net} = 495.004\text{ kJ}

  • D.

    Wnet=0 kJ,  qnet=496.000 kJW_{net} = 0\text{ kJ}, \; q_{net} = 496.000\text{ kJ}

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

MOT and Magnetic Nature|Reversible Expansion Work|Enthalpy Definition

Why This Question Is Tricky

Common Mistakes

This problem tests the integration of Molecular Orbital Theory (MOT) with chemical thermodynamics.

The first trap is identifying the correct number of unpaired electrons in \ce{O2} using MOT (x=2x=2) rather than a simple Lewis structure (x=0x=0).

The second trap is the conflation of ΔH\Delta H and ΔU\Delta U during the constant-volume dissociation step; students must subtract ΔngRT\Delta n_g RT to find the correct internal energy change.

The final, most lethal trap is forgetting that the number of moles of gas has doubled (n=2n=2) for the compression step, which directly affects the PΔVP\Delta V work calculation.

Quick Facts About This Question

Question Information

SubjectChemistry
ChapterChemical Bonding and Molecular Structure - Class 11 Part 1
ConceptMOT and Magnetic Nature
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree