Question

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

• A. $4\, RT$
• B. $9\, RT$
• C. $11\, RT$
• D. $15\, RT$

Answer 1

Answer: (C)

$11\, RT$

Answer 2

For two moles of diatomic oxygen with no vibrational mode.
$U_{1} = 2\times \frac{5}{2} RT = 5RT$
For four moles of monoatomic Argon,
$U_{2} = 4\times \frac{3}{2} RT = 6RT$
$\therefore\quad U=U_{1}+ U_{2} = 5RT+6RT=11RT$

Read more from the chapter:Internal Energy: Definition, Formula & Components