Question

2) Norepinephrine is a hormone released during stress. It is composed of carbon, hydrogen, oxygen, and nitrogen. The percent composition is 56.8% C, 6.56% H, 28.4% O, and 8.28% N. Find the empirical formula for norepinephrine.

Answer 1

Assume a basis of

m = 100 g of sample

then

56.8 g C

6.56 g of H

28.4 g of O

8.28 g of N

change all mass to mole

MW C = 12 g/mol

MW H = 1 g/mol

MW N = 14 g/mol

MW O = 16 g/mol

then

n C = m/MW = 56.8/12 = 4.7333

n H = m/MW = 6.56/1 = 6.56

n O = m/MW = 28.4/16 = 1.775

n N = m/MW = 8.28/14 = 0.591428

choose the smalles as basis, that is N

N:C = 4.7333/0.5914 = 8

N:H = 6.56/0.5914 = 11.08

N:O = 1.775/0.5914 = 3.00135

therefore, for a N = 1

we have

C8H11O3N1

or simply

C8H11O3N