Question

A diatomic gas is heated at constant pressure. What fraction of the heat energy is used to increase the internal energy?

• A. $\frac{3}{5}$
• B. $\frac{3}{7}$
• C. $\frac{5}{7}$
• D. $\frac{5}{9}$

Answer 1

Answer: (C)

$\frac{5}{7}$

Answer 2

Fraction of supplied energy which increases the internal energy is given by $f =\frac{\Delta U}{\left(\Delta Q_{p}\right)}=\frac{(\Delta Q)_{V}}{\left(\Delta Q_{p}\right)_{p}}$ $=\frac{\mu C_{V} \Delta T}{\mu C_{p} \Delta T}=\frac{1}{\gamma}$ For diatomic gas $\gamma=\frac{7}{5}$ $\Rightarrow f=\frac{5}{7}$