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JEE Advanced 2016Paper 1
Exam
JEE Advanced
Year
2016
Paper
Paper 1
Subject
Chemistry
Chapter
Thermodynamics (C)

JEE Advanced 2016 · Paper 1 · Chemistry · Thermodynamics (C)

One mole of an ideal gas at 300K in thermal contact with its...

One mole of an ideal gas at 300K300K in thermal contact with its surroundings expands isothermally from 1.0Lto2.0L1 . 0L to 2 . 0L against a constant pressure of 3.0atm3 . 0atm. In this process, the change in entropy of the surroundings \left(∆ {S}_{surr}\right) in J{K}^{- 1}is:<br/>(1Latm=101.3J)is:<br />\left(1Latm = 101 . 3J\right)

Options

  1. A5.7635 . 763
  2. B1.0131 . 013
  3. C−1.013- 1 . 013
  4. D−5.763- 5 . 763

Correct answer

C. −1.013- 1 . 013

Step-by-step solution

From 1st{1}^{st} law of thermodynamics,
qsys=∆U−w=0−[−Pext.∆V]{q}_{sys} = ∆ U - w = 0 - \left[- {P}_{ext} . ∆ V\right]
=3.0atm×(2.0L−1.0L)=3.0Latm= 3.0atm \times \left(2.0L - 1.0L\right) = 3.0Latm
∴∆Ssurr=(qrev)surrT=−qsysT∴ ∆ {S}_{surr} = \dfrac{{\left({q}_{rev}\right)}_{surr}}{T} = - \dfrac{{q}_{sys}}{T}
=−3.0×101.3J300K= - \dfrac{3.0 \times 101.3J}{300K}
=−1.013J/K= - 1 .013 J / K
Alternate solution:
∆Ssurr=qsurrT=−qsysT=WsysT∆ {S}_{surr} = \dfrac{{q}_{surr}}{T} = - \dfrac{{q}_{sys}}{T} = \dfrac{{W}_{sys}}{T}
∵∵ For the isothermal process:
∆U=0∆ U = 0 qsys=−Wsys{q}_{sys} = - {W}_{sys}
∆Ssurr.=−Pext(Vf−Vi)T∆ {S}_{surr.} = \dfrac{- {P}_{ext}\left({V}_{f} - {V}_{i}\right)}{T}
=−3(2−1)300×101.3= \dfrac{- 3 ( 2 - 1 )}{300} \times 101.3
=−1.013J/K= - 1.013J / K
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