When an ideal monoatomic gas is heated at constant pressure, the fraction of the heat energy supplied which…
When an ideal monoatomic gas is heated at constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is
$2 / 5$
$3 / 5$
$3 / 7$
$5 / 7$
Solution
By first law of thermodynamics
$Q=U+W$
$\begin{aligned} & \quad=\frac{f}{2} n R T+P \int d V=\frac{f}{2} n R T+P V \\ & \text { or } \quad Q=\frac{f}{2} n R T+n R T \quad(\because P V=n R T)\end{aligned}$
$=\frac{3}{2} n R T+n R T=\frac{5}{2} n R T$
Fraction of heat energy supplied $=\frac{U}{Q}$
$=\frac{(3 / 2) n R T}{(5 / 2) n R T}=\frac{3}{5}$
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