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Question:

Two moles of an ideal monoatomic gas occupies a volume V at 27°C. The gas expands adiabatically to a volume 2V. Calculate (a) the final temperature of the gas and (b) change on its internal energy.

(a)189K (b)𕒶.7kJ

(a)195K (b)2.7kJ

(a)189K (b)2.7kJ

(a)195k (b)𕒶.7kJ

Solution:

In an adiabatic process, PVγ=constant or TVγ-1=constant
T2/T1 = (V1/V2)γ-1
For monoatomic gas γ=5/3
T2 = (300K)(V/2V)(5/3)-1 = 189K
Change in internal energy ΔU = nCvΔT = 2(3/2)(253)(-111) = -6.7kJ