The empirical formula of a compound is determined to be CH, and its molecular mass is found to be 78.06 g/mol. Determine the molecular formula of the compound,

Question

How do you solve this? Also, what's an empirical formula?

Answer 1

The empirical formula tells you the simplest ratio between the elements in a molecule. CH means there are an equal number of carbon and hydrogen atoms in each molecule. There could be 2 carbon and 2 hydrogen, or 13 carbon and 13 hydrogen, etc. In other words, the molecular formula is C_xH_x, where x is a whole number.

 

One mole of C_xH_x has x moles of C and x moles of H. This means 1.01x + 12.01x = 78.06 (using the molar masses of H and C)

 

13.02x=78.06

 

x=78.06/13.02 = 6

 

So the molecular formula is C₆H₆