Question

The average degrees of freedom per molecule for a gas are $6$. The gas performs $25J$ of work when it expands at constant pressure. The heat absorbed by gas is

• A. $75J$
• B. $100J$
• C. $150J$
• D. $125J$

Answer 1

The correct option is B $100J$

We know that, change in internal energy $\Delta U=n{C}_v\Delta T=\frac{f}{2}\times nR\Delta T$
Where, f=no.of degrees of freedom$=6$
Also, work done at constant pressure, $\Delta W=nR\Delta T=25J$

Heat absorbed=$\Delta Q=\Delta U+\Delta W$

$=4nR\Delta T=4\times 25J$

$=100J$