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Question:

One mole of a monatomic ideal gas undergoes a cyclic process as shown in the figure (where V is the volume and T is the temperature). Which of the statements below is (are) true?

Process I is an isochoric process

In process IV, gas releases heat

In process II, gas absorbs heat

Processes I and II are not isobaric

Solution:

(A) Process-I is not isochoric, as we can see that V is decreasing. (B) Process-II is isothermal expansion ⇒ ΔU=0 but W>0 as volume is increasing ⇒ ΔQ>0 (C) Process-IV is isothermal compression, ⇒ ΔU=0 but W<0 as volume is decreasing ⇒ ΔQ<0 (D) Process-I and III are NOT isobaric because in isobaric process T∝V, hence isobaric T−V graph will be linear.