Question

A gas mixture consists of 2 moles of oxygen and 4 moles of Argon at temperature T. Neglecting all vibrational moles, the total internal energy of the system is

• A. 4RT
• B. 15RT
• C. 9RT
• D. 11RT

Answer 1

The correct option is D 11RT

Internal energy of 2 moles of oxygen
$U_2$ = $\mu \left(\frac{5}{2}RT\right)$
$=2.\frac{5}{2}RT$ = $5RT$
Internal energy of 4 moles of Argon.
$U_{AR}=\mu \left(\frac{3}{2}RT\right)$
$=4.\frac{3}{2}RT$ = $6RT$
$therefore$ Total internal energy
$U=U_{O_2}+U_{AR}$
$=11RT$