How do you solve for volume to volume conversions and empirical formula?

Question

Determine the molecular formula of the compound with an empirical formula of CH and a molar mass of 78.110 g/mol.

Answer 1

Simply divide the molar mass of the empirical formula into the molar mass of the molecular formula to find the multiple. Here, molar mass of CH = 13. Divide 78.11 by 13 to get 6.

Molecular formula = C₆H₆

Answer 2

Hello, Jaida,

The formula unit is CH, so there is 1 H for every 1 C. Set up a table with the two elements and their atomic masses, which are also their molar masses. Guess at a value for the number of C atoms, at 12 g/mole each) that would take us close to 78.11 g/mole, without going over.

6 would get us to 72. The number of hydrogens is the same as the number of carbons, so add 6 to the molar mass of the compound. The sum of 72 (from the carbons) and 6 (from the hydrogens) is close enough, for me, to the 72.110 g/mole specified. I used rounded numbers for the atomic masses, so use the more precise values in your work.

That means there are 6 each of the carbon and hydrogen. The formula is C₆H₆.

Bob