Empirical Formula Practice

Question

Lactic acid, employed in pharmaceutical technology to produce water-soluble lactates, has the following elemental composition: C, 40.00 ; H, 6.71 ; O, 53.29 .

Calculate the empirical formula of lactic acid.    

Express your answer as a chemical formula.

Answer 1

You left out units for the numbers you presented. We will assume these are percentage by mass.

Assume you have 100 g

C = 40% = 40.00 g C x 1 mol C / 12 = 3.33 moles C

H = 6.71% = 6.71 g H x 1 mo Hl / 1 g = 6.71 moles H

O = 53.29% = 53.29 g O x 1 mol O / 16 g = 3.33 moles O

The ratio of moles of C : H : O = 3.33 : 6.6 : 3.33 which is the same as 1 : 2 : 1

Empirical formula = CH₂O