Barrons SAT Subject Test Chemistry, 13th Edition

52. (E) To find the simple or empirical formula, divide each % by the element’s
    atomic mass.

Carbon

40 ÷ 12 = 3.333

Hydrogen

6.67 ÷ 1 = 6.67

Oxygen

53.33 ÷ 16 = 3.33

Next, divide each quotient by the smallest quotient in an attempt to get

small whole numbers.

3.33 ÷ 3.33 = 1 C

6.67 ÷ 3.33 = 2 H

3.33 ÷ 3.33 = 1 O

The simplest formula is CH 2 O, which has a molecular mass of 30. The

true molecular mass is given as 90.0, which is three times the simplest.

Therefore, the true formula is C 3 H 6 O 3.