Empirical formula

Clari

A gas X has a density of 1.187[tex]gdm^-3[/tex] at 1.01 atm. & 35[tex]^oC[/tex]. 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 [tex]C_{7}H_{20}[/tex] while I don't think there is a gas with this formula, the closest one is [tex]C_{7}H_{16}[/tex]. 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 [tex]CH_{3}[/tex].

Sirus

Ok.

Note: to make your Latex fit into the text, use "itex" and "/itex" in the brackets instead of "tex" and "/tex".

chem_tr

It is very simple; just simplify the ratio, [itex] \frac {7}{20} [/itex] to obtain [itex] \frac {1}{0,35}[/itex]. 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.