Molecular Formula 1

Molecular Formula: The actual formula for a molecule.

Problem:

A compound has an empirical formula of ClCH₂ and a molecular weight of 98.96 g/mol. What is its molecular formula?

Strategy:

1. Find the mass of the empirical unit.
   
   Mass of empirical unit = mass Cl + mass C + 2(mass H)

   Mass of empirical unit = 35.45 + 12.00 + 2(1.008) = 49.47 g/mol
   
   

2. Figure out how many empirical units are in a molecular unit.
   
   # of empirical units = (mass of molecular unit/ mass of empirical unit)

   (98.96 g/mol) / (49.47 g/mol) = 2.000 empirical units per molecular unit
   
   

3. Write the molecular formula.
   
   It takes two empirical units to make a molecular unit, so, the molucular formula is:

   Cl₂C₂H₄

More difficult example