A mixture of `NO_2 and N_2O_4` has a vapour density of 38.3 at 300 K. What is the number of moles of `NO_2` in 100 g of the mixture?

Options

A. 0.43
B. 4.4
C. 3.4
D. 3.86

Answer

A

Explanation

Suppose weight of `N_2O_4 = xg`
Suppose weight of `NO_2 = 100-xg`
Total no. of moles `= x/92 +(100-x)/46`
But molecular mass of the mixture `= 2 xx 38.3 = 76.6`
`implies " Total no. of moles in the mixture " = 100/76.6 = 1.3`
`implies 1.3=x/92+(100-x)/46 implies x=80 and 100-x=20`
`implies " No. of " (NO_2) = 20/46 = 0.434`