A sample of ideal gas `(gamma = 1.4)` is heated at constant pressure. If an amount `140 J` of heat is supplied to the gas, find (a) the changes in internal energy of the gas, (b) the work done by the gas.

Explanation

Suppose the simple contains `n` moles. Also suppose the volume changes from `V_(1)` to `V_(2)` and the temperature changes from `T_(1)` and `T_(2)`.
The heat supplied is
`Delta Q = Delta U + P Delta V = Delta U + n R Delta T = Delta U + (2 Delta U)/(f)`
a. The change in internal energy is
`Delta U = n (f)/(2) R (T_(2) - T_(1)) = (f)/(2) R n (T_(2) - T_(1))`
`= (f)/(2 + f) Delta Q = (140 J)/(1.4) = 100 J`
b. The work done by the gas is
`Delta W = Delta Q - Delta U = 140 J - 140 J - 100 J = 49 J`