Question

An unknown compound has the empirical formula CH if the molar mass is determined to be 26 g/mol what is the molecular formula?

Answer 1

`C_2H_2` or acetylene

Explanation:

Well, a `CH` compound would have a molar mass of `12.0107 \ "g/mol"+1.008 \ "g/mol"=13.0187 \ "g/mol"`.

If its real mass is `26 \ "g/mol"`, then we have to divide it by the empirical mass to get the "scale number", which is:

`(26color(red)cancelcolor(black)("g/mol"))/(13.0187color(red)cancelcolor(black)("g/mol"))~~2`

And so, we multiply the formula by `2`, and we get:

`CH*2=C_2H_2`

Turns out that this compound is called acetylene, the simplest alkyne.