An elemental analysis of the acid indicates that it is composed of 5.89% H, 70.6% C, and 23.5% O by mass. What is its molecular formula?

Empirical formula of acid is = C₄H₄O

In order to find the molecular formula we must have molar mass of compound. Because,

Molecular formula = n * (empirical formula)

n = molar mass of compound / empirical formula mass

Explanation:

No. of gram atoms of carbon = 70.6 g / 12 g/mol = 5.88 g atom

No. of gram atoms of hydrogen = 5.89 g / 1.008 g/mol = 5.84 g atom

No. of gram atoms of oxygen = 23.5 g / 16 g/mol = 1.47 g atom

Atomic ratio:

C : H : O 5.88 / 1.47 : 5.84 / 1.47 : 1.47 / 1.47

C : H : O 4 : 4 : 1

empirical formula of acid is = C₄H₄O

Molecular formula:

Molecular formula = n * (empirical formula)

n = molar mass of compound / empirical formula mass

empirical formula mass = 4 * 12 + 4 * 1.008 + 1 * 16

empirical formula mass = 48 + 4.032 + 16 = 68.032