A 175.0 g sample of a compound contains 56.15 g #C#, 9.43 g #H3, 74.81 g #O#, 13.11 g #N#, and 21.49 g #Na.# What is its empirical formula?
We calculate (i) the percentage composition, and then (ii) the emprical formula, to give an empirical formula of
We need the percentage composition of each element:
Given this percentage makeup, we can work out an empirical formula by (i) assuming that there are
Now we divide each molar quantity thru by the SMALLEST MOLAR QUANTITY, that of nitrogen, to give an empirical formula of
Now of course, I have done this the long way round, and made a real meal out of the the problem. I could have missed the step where the percentages are calculated, and been a bit more direct. I did it the long way, because often you are quoted percentage composition by mass in empirical formula problems.