Question

Two moles of helium are mixed with $n$ moles of hydrogen. If $\frac{C_P}{C_V}=\frac{3}{2}$ for the mixture, then the value of $n$ is

• A. $3/2$
• B. $2$
• C. $1$
• D. $3$

Answer 1

The correct option is B $2$

For a given mixture of gases,

$(n_1+n_2)$ /($Y-1$) = $n_1$/($Y_1-1$) $+$ $n_2/$($Y_2-1$)

put $n_1=2$, $Y=3/2$, $Y_1=5/3$, $Y_2=7/5$

solving the required equation as

$(2+n)$/$(3/2-1)$ = $2/(5/3-1)$ + $n/(7/5-1)$

$n=2$