In the reaction  $CO+O_2\to C{O}_2;N_2+O_2\to NO.$ 

10ml of mixture containing CO and $N_2$ required 7ml oxygen to form $C{O}_2$ and NO, on combustion. The volume of $N_2$ in the mixture will be _________ ml.

$CO\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to C{O}_2\left(g\right)$                $N_2\left(g\right)+O_2\left(g\right)\to 2N\left(g\right)$

$x$                            $\frac{x}{2}$                                                 y           y 

x+y = 10  – (1)

$\frac{x}{2}+y=7 – \left(2\right).$

From 1 & 2  x = 6,  y = 4