A compound is found to contain 15.12 % phosphorus, 6.841 % nitrogen, and 78.03 % bromine by weight.

what is the emperical formula

3 answers

I notice the percents don't add up to 100%.
Take a 100 g sample which gives you
15.12 g P,
6.841 g N
78.03g Br

Convert to mols.
15.12/31 = mols P
6.841/14 = mols N
78.03/80 = mols Br

Now find the ratio of those mols to each other with no number being less than 1.00. The easy way to do that is to divide the smallest number by itself (thereby assuring it is 1.00), then do then divide the other numbers by the same small number. Round to whole number.

PNBr2