Question

If one mole of a monoatomic gas $(r=\frac{5}{3})$ is mixed with one mole of a diatomic gas $(r=\frac{7}{5})$, the value of ‘r’ of the mixture is

• A. 1.4
• B. 1.5
• C. 1.53
• D. 3.07

Answer 1

The correct option is B 1.5

For a mono atomic gas, $C_v=\frac{3R}{2}$ and for a diatomic gas, $C_v=\frac{5R}{2}$. Since one mole of each gas is mixed together, the C_V of the mixture will
$C_v=\frac{1}{2}[\frac{3R}{2}+\frac{5R}{2}]=2R$
As $C_P=R+C_V=R+2R=3R$
$\therefore r=\frac{C_P}{C_V}=\frac{3R}{2R}=1.5$