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NEET 2026
Exam
NEET
Year
2026
Subject
Chemistry
Chapter
Chapter

NEET 2026 · Chemistry · Chapter

Calculate the work done when 5 moles of an ideal gas expand...

Calculate the work done when 55 moles of an ideal gas expand isothermally and reversibly from a volume of 2 L2 \text{ L} to 20 L20 \text{ L} at 27∘C27^{\circ}\mathrm{C}.
(Given R=8.314 J K−1 mol−1R = 8.314 \text{ J K}^{-1} \text{ mol}^{-1})

Options

  1. A−28.72 kJ-28.72 \text{ kJ}
  2. B−12.47 kJ-12.47 \text{ kJ}
  3. C−5.74 kJ-5.74 \text{ kJ}
  4. D+28.72 kJ+28.72 \text{ kJ}

Correct answer

A. −28.72 kJ-28.72 \text{ kJ}

Step-by-step solution

For an isothermal reversible expansion of an ideal gas, the work done is given by:

W=−2.303nRTlog⁡(V2V1)W = -2.303 nRT \log \left( \dfrac{V_2}{V_1} \right)

Given:
n=5 moln = 5 \text{ mol}
R=8.314 J K−1 mol−1R = 8.314 \text{ J K}^{-1} \text{ mol}^{-1}
T=27∘C=27+273=300 KT = 27^{\circ}\mathrm{C} = 27 + 273 = 300 \text{ K}
V1=2 LV_1 = 2 \text{ L}
V2=20 LV_2 = 20 \text{ L}

Substituting the values into the formula:

W=−2.303×5×8.314×300×log⁡(202)W = -2.303 \times 5 \times 8.314 \times 300 \times \log \left( \dfrac{20}{2} \right)

W=−2.303×12471×log⁡(10)W = -2.303 \times 12471 \times \log(10)

W=−28720.7 JW = -28720.7 \text{ J}

W≈−28.72 kJW \approx -28.72 \text{ kJ}

Answer: −28.72 kJ-28.72 \text{ kJ}
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