Question

When an ideal diatomic gas is heated at constant pressure the fraction of the heat energy supplied which increases the internal energy of the gas is

• A. $\frac{2}{5}$
• B. $\frac{3}{5}$
• C. $\frac{3}{7}$
• D. $\frac{5}{7}$

Answer 1

Answer: (D)

$\frac{5}{7}$

Answer 2

The desired fraction is
$f=\frac{\Delta U}{\Delta Q}=\frac{nC_v \Delta T}{nC_p\Delta T}=\frac{C_v}{C_p}=\frac{1}{\gamma} \, \, or \, \, f=\frac{5}{7}$ $\, \, \, \, \, \, \, \bigg(as \gamma=\frac{5}{7}\bigg)$
$\therefore \, \, \, \,$ Correct option is (d).