Heat is supplied to a diatomic gas at constant pressure.
The ratio of `DeltaQ : DeltaU : DeltaW` is

Options

A. `2 : 3 : 5`
B. `5 : 3 : 2`
C. `2 : 5 : 7`
D. `7 : 5 : 2`

Answer

D

Explanation

For a diatomic gas, `C_(P)=7/2RandC_(V)=5/2R`
Consider n moles of a diatomic gas.
Then `DeltaQ=nC_(P)dT=n(7/2R)dT" "....(1)`
`DeltaU=nC_(V)dT=n(5/2R)dT" "....(2)`
`becauseDeltaQ=DeltaU+DeltaW`
`thereforeDeltaW=DeltaQ-DeltaU`
`thereforeDeltaW=nRdT(7/2-5/2)=n(2/2R)dT" "...(3)`
`therefore` From (1), (2) and (3),
`thereforeDeltaQ:DeltaU:DeltaW=7:5:2`