Question

A gas is found to have formula $(CO)_n$. If its vapour density is 56, the value of n will be:
(a) 7
(b) 5
(c) 4
(d) 3

Answer 1

Mol.wt=2×× vapour density

⇒2×70=140⇒2×70=140

Now mol.mass of [CO]x[CO]x is (12+16)x=28x(12+16)x=28x

∴28x=140∴28x=140

⇒x=5⇒x=5

Hence (b) is the correct answer.

Answer 2

$\textbf{Answer}$

(c) 5

$\textbf{Explanation}$

Molecular weight Of C = 12u

Molecular Weight Of O = 16u

So..

Molecular Weight Of (CO)n = (12+16)n

= 28n

Now,

Molecular Weight (Mass) = 2 × vapour density

28n = 2 × 70

28n = 140

n = $\dfrac{140}{28}$

$\boxed{n\: =\: 5}$