A sample of ideal gas `(gamma = 1.4)` is heated at constant pressure. If `140 J` of heat is supplied to gas, find `DeltaU` and W`.

Explanation

Gas is diatomic as `gamma = 1.4`, thus , `C_(V) = (5)/(2)R` and `C_(P) = (7)/(2) R`.
Given, `DeltaH = 140 J` at constant pressure
`:. DeltaH = qp = n xx C_(P) xx DeltaT`
Aslo, `DeltaT = (140)/(nC_(P)) = (140 xx2)/(7n xxR) = (40)/(n)`
Now, `W =- nRT DeltaT =- n xx2 xx (40)/(n) =- 80J`
Also, `qp - DeltaH = DeltaU + (-W)`
`DeltaU = DeltaH + W = 140 - 80`
`DeltaU = 60J`