Question

A compound is found to be 51.39% carbon, 8.64% hydrogen, and 39.97% nitrogen. It has a molecular molar mass of 140.22 g/mol. (This question requires one to find the empirical formula to end up with the final answer in molecular formula)
A. C10H14N2
B. C7H9N
C. C6H12N4
(The numbers are supposed to be subscripts)
I tried this problem by converting the percentages to grams, then dividing each element by its atomic mass, and lastly dividing each one by the lowest quotient. However, for the empirical formula I got C2H3N, which is wrong when you want to calculate the molecular formula using the empirical formula. Please help!

Answer 1

your technique should work
... not sure about the last "lowest quotient" step

C ... 140.22 * .5139 / 12.011 = 5.999
H ... 140.22 * .0864 / 1.0079 = 12.02
N ... 140.22 * .3997 / 14.007 = 4.001

looks like C.

Answer 2

thank you!