Question

In thermodynamics process pressure of a fixed mass of gas is changed in such a manner that the gas releases $30J$ of heat and $18J$ of work was done on the gas. If the initial energy of the gas was $60J$ then, the final internal energy will be:

• A. $32J$
• B. $48J$
• C. $72J$
• D. $96J$

Answer 1

Answer: (B)

$48J$

The change in the internal energy of the system, U = Q - W
Q = -30
W = -18
Hence, $U=-12$
Thus, if the initial internal energy is $60J$,
the final energy x is given by,

$x-60=-12$

or, $x=48J$