## Empirical formula

A gas X has a density of 1.187$$gdm^-3$$ at 1.01 atm. & 35$$^oC$$. Gas X contains 79.8% by mass of C & 20.2% by mass of H. Find the empirical formula of X.

Here are my steps:

mole ratio of C to H = 79.8/12.01 : 20.2/1.008
= 7: 20
In that case, its empirical formula is $$C_{7}H_{20}$$ while I don't think there is a gas with this formula, the closest one is $$C_{7}H_{16}$$. Can anyone help me with it?

I know what's wrong now....I have mistaken it as the molecular formula...hheee...being silly...so the answer should be $$CH_{3}$$.
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 Recognitions: Gold Member Science Advisor It is very simple; just simplify the ratio, $\frac {7}{20}$ to obtain $\frac {1}{0,35}$. As you know that a carbon-containing gas must contain up to five carbon atoms, a gas with seven carbons would not be logical. So just simplify the ratio for your needs.

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