(a) An ideal gas contained in a cylinder is given 200 J of heat. The gas does 60 J of work in the expansion resulting from heating. Calculate the increase in internal energy in the process.
(b) Calculate the change in internal energy of a gas kept in a rigid container when 150 J of heat is supplied to it.

Explanation

(a) According to first law of thrmodynamics
`DeltaQ=DeltaU+DeltaW`
`200=DeltaU+60`
`DeltaU=140J`
(b) Since gas is kept in rigid container hence, its volume remains same.
`DeltaV=0`,`DeltaW=0`
from first law.
`DeltaQ=DeltaU+DeltaW`
`150=DeltaU+0`
`DeltaU=150J`