Question

$5$moles of oxygen are heated at constant volume from ${10}^{0}C$ to ${20}^{0}C$. The change in internal energy of the gas is:

$C_p=7.03calmo{l}^{-1}{K}^{-1}$ and $R=8.31Jmo{l}^{-1}{K}^{-1}$

• A. $125cal$
• B. $252cal$
• C. $50cal$
• D. $500cal$

Answer 1

The correct option is B $252cal$

$\Delta U=n{C}_V\Delta T$
Also, $C_P-C_V=R$
$⟹7.03-C_V=\frac{8.31}{4.18}=1.98$
Now, $C_V=5.05;n=5;\Delta T=10$
$\therefore \Delta U=5\times 5.05\times 10=252.5\approx 252cal$