One gram of an element was found to contain 0.835 gram of chlorine its vapour density is 85. Find the molecular formula of chloride.

Wt. of element = 1-0.835 = 0.165 gm

eq. wt of element =$\frac{0.165}{0.835}\times 35.5=7.014$

Let x be the valency of element

At. wt of element = 7.014 x

the molecular formula of chloride $MC{l}_x$

M.wt of chloride = 7.014x + x.35.3=V.D. × 2

(42.314)x = 2 × 85

$\therefore$ x = 4

Hence molecular formula = $MC{l}_4$