The compound adrenaline contains 56.79% c, 6.56% h, 28.37% o, and 8.28% n by mass. what is the empirical formula for adrenaline?

To determine the empirical formula of the compound given, we need to determine the ratio of each element in the compound. To do that we assume to have 100 grams sample of the compound with the given composition. Then, we calculate for the number of moles of each element. We do as follows:
         mass        moles
C       56.79        4.73
H       6.56          6.50
O       28.37        1.77
N      8.28           0.59

Dividing the number of moles of each element with the smallest value, we will have the empirical formula:

         moles                 ratio
C       4.73     / 0.59       8
H       6.50     / 0.59      11
O       1.77     / 0.59       3
N        0.59    / 0.59       1

The empirical formula would be C8H11O3N.