Question

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

• A. $2/5$
• B. $3/5$
• C. $3/7$
• D. $3/4$

Answer 1

The correct option is B $3/5$

$\delta Q=du+Pdv$

$pv=nRT$

$Pdv=nRdT$

$\delta Q=n{C}_{V}dT+nRdT$

$\delta Q=n(C_v+R)dT$

$\delta Q=n{C}_{p}dT$

$\frac{du}{\delta Q}=\frac{n{C}_{V}dT}{n{C}_{p}dT}$

$\frac{c_p}{c_v}=\gamma =\frac{5}{3}$

$\frac{du}{\delta Q}=\frac{3}{5}$