Question

A sample of a certain organic acid has a mass of 5.000 g. Elemental analysis of this compound found it to contain 1.334 g C, 3.554 g O, and the rest of the mass is hydrogen. If the molar mass of the organic acid is 90.03 g/mol, determine its molecular formula.

Answer 1

C₂H₂O₄

Step-by-step explanation:

Given parameters:

Mass of organic acid = 5g

Mass of C = 1.334g

Mass of O = 3.554g

Mass of H = 5 - (1.334 + 3.554) = 0.112g

Molar mass = 90.03g/mol

Unknown:

Molecular formula of the compound = ?

Solution:

To solve this problem, we find the empirical formula of the compound first. It is the simplest formula of the compound.

Elements C H O

Mass 1.334 0.112 3.554

Molar mass 12 1 16

Number of moles 1.334/12 0.112/1 3.554/16

0.112 0.112 0.222

Divide by the

Smallest 0.112/0.112 0.112/0.112 0.222/0.112

1 1 2

Empirical formula = CHO₂

The molar mass of this empirical formula = 12 + 1 + 2(16) = 45g/mol

Now;

Multiplication index =
`(90.03)/(45)` = 2

Molecular formula = (CHO₂)₂ = C₂H₂O₄