Question

The empirical formula of a compound is CH. The experimental molar mass is 78.12 g/mol. How do you determine the molecular formula of the compound?

Answer 1

The `"molecular formula"` is always a whole number multiple of the `"empirical formula"`.

Explanation:

And thus: `"molecular formula"=nxx"(empirical formula)"`.

We take the given empirical formula, work out its mass, and then solve for `n`.

So `78.23*g*mol^-1=nxx(12.011+1.00794)*g*mol^-1`

Where of course, `12.011` and `1.00794` are the atomic masses of carbon and hydrogen in `g*mol^-1`,

`n=(78.23*g*mol^-1)/((12.011+1.00794)*g*mol^-1)=6`

And thus the molecular formula `-=` `(CH)_6` or `C_6H_6`. What is the likely name of this molecule?