Question

If a gas mixture contains 2 moles of $O_2$ and $4$ moles of $Ar$ at temperature $T$, then what will be the total energy of the system (neglecting all vibrational modes)

• A. $11\, RT$
• B. $15 \, RT$
• C. $8 \, RT$
• D. $RT$

Answer 1

Answer: (A)

$11\, RT$

Answer 2

Total energy
$U=2\left(\frac{n_{1}}{2} R T\right)+4\left(\frac{n_{2}}{2} R T\right)$
For $O _{2}, n=5$ and for $Ar , n_{2}=3$
$\therefore U =2\left(\frac{5}{2} R T\right)+4\left(\frac{3}{2} R T\right)$
$=11\, R T$