Question

One mole of monatomic gas is mixed with three moles of a diatomic gas. The molar specific heat of the mixture at constant volume is

• A. 2R
• B. 9R
• C. 2.25R
• D. 3R

Answer 1

Answer: (C)

2.25R

$N{C}_{mix}=n_1{C}_{v1}+n_2{C}_{v2}$

$C_{mix}=\frac{n_1{C}_{v1}+n_2{C}_{v2}}{n_1+n_2}=\frac{1\left(\frac{3R}{2}\right)+3\left(\frac{5R}{2}\right)}{(1+3)}=\frac{\frac{15R}{2}}{4}=\frac{9R}{4}=2.25R$

Hence, option C is correct.