Two moles of oxygen is mixed with eight moles of helium. The effective specific heat of the mixture at constant volume is

Options

A. A)1.3R
B. B)1.4R
C. C)1.7R
D. D)1.9R

Answer

C

Explanation

Let for mixture of gases, specific heat at constant volume be `C_(v)`.
`C_(v)=(n_(1)(C_(V))_(1)+n_(2)(C_(V))_(2))/(n_(1)+n_(2))`
where for oxygen, `C_(V_(1))=(5R)/(2),n_(1)=2mol`
For helium, `C_(V_(2))=(3R)/(2),n_(2)=8mol`
Therefore,
`C_(V)=((2xx5R)/(2)+8xx(3R)/(2))/(2+8)`
`=(17R)/(10)=1.7R`