Calculating Empirical Formulas from Percentage Compositions & Molecular Formulas

What's step 1 on working out empirical formulas from the percentages of different elements?

Assume you're got 100g of the compound, so you can turn the percentages into masses, then work out how many motes of each element are in 100g of the compound,

What's step 2 on working out empirical formulas from the percentages of different elements?

Divide each number of moles by the smallest number of moles you found in step 1, which gives you the ratio of the elements in the compound.

What's step 3 on working out empirical formulas from the percentages of different elements?

Apply the numbers from the ratio to the formula.

What might you only be given sometimes?

The percentage of some of the elements in the compound.

What will you have to do if you're only given some of the element?

You'll have to work aut the percentages of the others.

What do you need to work out the molecular formula?

Empirical formula and molar mass.

What happens when dividing the molar mass by the mass of the empirical formula?

It tells you what factor you need to scale the empirical formula up by to get the molecular formula.