In changing the state of a gas adiabatically from an equilibrium state A to another equilibrium state B an amount of work equal to 22.3 J is done on the system.If the gas is taken from state A to B via a process in which the net heat absorbed by the system is 9.35 cal then the net work done by the system in latter case is
(Take 1 case =4.2 J)

Options

A. 15 J
B. 16 J
C. 17 J
D. 18 J

Answer

C

Explanation

In the first case
For adiabatic change `DeltaQ=0`
The work is donw on the system is
`DeltaW=-22.3 J`
According to first law of thermodynamics
`DeltaQ=DeltaU+DeltaW`
`0=DeltaU-22.3`
`DeltaU=22.3 J`
In the second case
`DeltaQ =9.35 cal = 9.35xx4.2 J` =39.3 J
As `Delta Q=DeltaU+DeltaW`
`DeltaW=DeltaQ-DeltaU`
`DeltaW =39.3-22.3 =17J`