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Heat and Thermodynamics question

2022 · 24 Jun · Shift 2 · Q70
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Heat and Thermodynamics question

2022 · 24 Jun · Shift 2 · Q70

JEE MainPhysicsHeat and ThermodynamicsNumerical+4 / −1
A monoatomic gas performs a work of Q4{Q \over {4}}4Q​ where Q is the heat supplied to it. The molar heat capacity of the gas will be ‾\underline{\hspace{2cm}}​ R during this transformation. Where R is the gas constant.
Numerical answer
View written solutionFree

Correct answer: 2

  1. Let the molar heat capacity during the process be CCC.

  2. For 111 mole of an ideal monoatomic gas, Q=C ΔTQ = C\,\Delta TQ=CΔT

  3. The work done is given as W=Q4W = \frac{Q}{4}W=4Q​

  4. From the first law of thermodynamics, Q=ΔU+WQ = \Delta U + WQ=ΔU+W

  5. For a monoatomic ideal gas, ΔU=nCVΔT=3R2ΔT\Delta U = nC_V\Delta T = \frac{3R}{2}\Delta TΔU=nCV​ΔT=23R​ΔT for n=1n=1n=1 mole.

  6. Substitute into the first law: Q=3R2ΔT+Q4Q = \frac{3R}{2}\Delta T + \frac{Q}{4}Q=23R​ΔT+4Q​

  7. Rearranging, Q−Q4=3R2ΔTQ - \frac{Q}{4} = \frac{3R}{2}\Delta TQ−4Q​=23R​ΔT 3Q4=3R2ΔT\frac{3Q}{4} = \frac{3R}{2}\Delta T43Q​=23R​ΔT

  8. Hence, Q=2RΔTQ = 2R\Delta TQ=2RΔT

  9. Comparing with Q=CΔTQ = C\Delta TQ=CΔT we get C=2RC = 2RC=2R

  10. Therefore, the required value is 2\boxed{2}2​ times RRR.

Comparison with stored answer:

  • Derived answer: 222
  • Stored correct answer: 222
  • They match.
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