Question

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

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

Answer 1

The correct option is B 100 J

We know the relation
$△U=\frac{f}{2}\times nR△T=3nR△TAlso,△W=-P△V=-nR△T=-25J.......1\text{From Ist law of thermodynamic},△Q=△U+△W=3nR△T+nR△T=4nR△T=4\times 25=100J......\text{from equation 1}$
Hence, heat absorbed by the gas is 100 J.