Question

Resorcinol is an antiseptic and disinfectant that is an active ingredient in many over the counter medical creams, including Clearasil and Vagisil. A 0.3894 g sample of resorcinol was subjected to combustion analysis, producing 0.9338 g of CO2 (M = 44.01 g/mol) and 0.1911 g of H2O (M = 18.02 g/mol). What is the empirical formula of resorcinol, assuming it only contains carbon, hydrogen, and oxygen?

Answer 1

moles of CO2 = 0.9338/ 44.01 = 0.02133

moles of C= 0.02133

mass of Carbon = 12 x 0.02133= 0.256 g

moles of H2O = 0.1911 / 18.02 = 0.01060

moles of H = 2 x 0.01060 = 0.02121

mass of hydroegen = 0.02121 g

Oxygen mass = 0.3894 - (0.256+ 0.02121 ) = 0.1122 g

moles of O = 0.1121 /16 = 7.01 x 10^-3

C                O               H

0.02133     7.01 x 10^-3       0.02121

3                 1                    3

C3H3O -----------------------> empirical formula

empirical formula = C3H3O