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 $100J$

At constant pressure, the ratio of heat supplied to the work done is given by,
$\frac{Q}{W}=C_p$
Now, degrees of freedom are 6, i.e $C_v=\frac{fR}{2}=3R$
Thus, $C_p=C_v+R$
$C_p=4R$
Hence, $Q=25$ $\times$4$=100J$