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At `27^@C` two moles of an ideal monatomic gas occupy a volume V. The gas expands adiabatically to a volume `2V`. Calculate (a) final temperature of the gas (b) change in its internal energy and (c) the work done by the gas during the process. [ `R=8.31J//mol-K`] |
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Answer» Correct Answer - A::B::C (a) In case of adiabatic change `TV^(gamma-1)=` constant So that `T_1V_1^(gamma-1)=T_2V_2^(gamma-1)` with `gamma=(5/3)` i.e. `300xxV^(2//3)=T(2V)^(2//3)` or `T=(300)/((2)^(2//3))=189K` (b) As `DeltaU=nC_VDeltaT=n(3/2R)DeltaT So, `DeltaU=2xx(3/2)xx8.31(189-300)` `=-2767.23J` Negative sign means internal energy will decrease. (c) According to first law of thermodynamics `Q=DeltaU+DeltaW` And as for adiabatic change `DeltaQ=0` `DeltaW=-DeltaU=2767.23J` |
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