Question

In a thermodynamic process, pressure of a fixed mass of gas is changed in such a manner that the gas releases 20 joule of heat and 8 joule of work was done on the gas. If the initial internal energy of the gas was 30 joule, then the final internal energy will be :

• A. $2joule$
• B. $18joule$
• C. $42joule$
• D. $58joule$

Answer 1

The correct option is B $18joule$

According to first law of thermodynamics $\Delta Q=\Delta W+\Delta U$
Substituting values will give,
$-20=-8+(U_f-30$)
$U_f=18J$