Question

When an ideal diatomic gas is heated at constant pressure, the fraction of heat energy supplied which is used in doing work to maintain pressure constant is

• A. $5/7$
• B. $7/2$
• C. $2/7$
• D. $2/5$

Answer 1

Answer: (A)

$5/7$

A)

$$\begin{array}{c}\text{The desired fraction is:}\\ f=\frac{\Delta U}{\Delta Q}=\frac{n{C}_V\Delta T}{n{C}_P\Delta T}=\frac{C_V}{c_P}=\frac{1}{\gamma }\\ \text{or}f=\frac{5}{7}(as\gamma =\frac{7}{5})\\ \text{internal energy of the system is}5/7\end{array}$$