Acompound is 80.0% carbon and 20.0% hydrogen by mass. assume you have a 100.-g sample of this compound.

The empirical formula is:

Explanation:

In a sample of 100 g:

To determine the molecular formula you need to calculate the moles of each element. To do that the atomic weights are needed:

So, the moles of each one:

Now, you need to take this values to non-fractional numbers (keeping the ratio):

Therefore the empirical formula is:

The molecular formula probably is a multiple of the empirical due to the carbon's valence.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).