A white powder used in paints, enamels, and ceramics has the following percentage composition Ba = 69.6%, C = 6.09% and O = 24.3%. What is the subscript associated with Carbon in the empirical formula for the compound?

Answer 1

Take a 100 g sample. You will have Ba = 69.6 g, C = 6.09 g and O = 24.3 g.
mols Ba = 69.6/137.3 = 0.507
mols C = 6.09/12 = 0.507
mols O = 24.3/16 = 1.52
To find the empirical formula you find the ratio of those three elements in small whole numbers with the smallest being 1.00. The easy way to do that is to divide the smallest number by itself (you know that gets you 1.00), then divide the other numbers by the same small number, like this.
Ba = 0.507/0.507 = 1
C = 0.507/0.507 = 1
O = 1.52/0.507 = 2.99 which rounds to 3.0 so the empirical formula must be BaCO3. So C must be ........