C = 12.818 mg CO2 (1 mmol CO2/44 mg CO2) (1 mmol C/1 mmol CO2) = 0.29 mmol
H = 3.675 mg of H2O (1 mmol H2O/18 mg H2O) (2 mmol H/1 mmol H2O) = 0.41 mmol
N = (4.725 mg – 0.29 * 12 – 0.41 * 1) * (1 mmol/14 mg) = 0.06 mmol
Divide everything by the smallest number:
C = 0.29/0.06 = 4.8 ~ 5
H = 0.41/0.06 = 6.8 ~ 7
N = 0.06/0.06 = 1
Empirical formula is:
C5H7N