Thermodynamics

JEE Main level, numerical answer, medium

118 of 190

Question 118 of 190

A diatomic gas (γ=1.4)\left(\gamma =1.4\right) does 400J400J of work when it is expanded isobarically. The heat given to the gas in the process is _____ JJ.

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Answer: 1400

For isobaric process: W=nRΔTW=nR\Delta T⇒400=nRΔT\Rightarrow 400=nR\Delta T
Also:
Q=nCpΔTQ=n{C}_{p}\Delta T
⇒Q=n(7R2)ΔT\Rightarrow Q=n\left(\dfrac{7R}{2}\right)\Delta T (Cp=7R2{C}_{p}=\dfrac{7R}{2}, for diatomic gas)
Q=72×400=1400JQ=\dfrac{7}{2}\times 400=1400J

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