Valproic acid, used to treat seizures and bipolar disorder, is composed of C, H, and O. A 0.165-g sample is combusted to produce

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Valproic acid, used to treat seizures and bipolar disorder, is composed of C, H, and O. A 0.165-g sample is combusted to produce

0.166 g of water and 0.403 g of carbon dioxide. What is the empirical formula for valproic acid? If the molar mass is 144 g>mol, what is the molecular formula?

Chemistry

1 answer:

VMariaS [1K] · Answer 1 · 2026-02-26T11:30:10+03:00

Answer:

The empirical formula is = $C_4H_8O$

The Valproic acid formula is = $C_8H_{16}O_2$

Explanation:

Mass of the produced water = 0.166 g

Molar mass of water = 18 g/mol

The moles of $H_2O$ are calculated as 0.166 g /18 g/mol = 0.00922 moles.

In 1 mole of water, there are 2 moles of hydrogen atoms.

Thus,

Moles of H = 2 x 0.00922 = 0.01844 moles

Each hydrogen atom's molar mass is 1.008 g/mol.

Hydrogen mass in the molecule = 0.01844 x 1.008 = 0.018588 g

Mass of produced carbon dioxide = 0.403 g

Molar mass of carbon dioxide = 44.01 g/mol

The moles of $CO_2$ are calculated as 0.403 g /44.01 g/mol = 0.009157 moles.

Each carbon atom's presence is 1 mole in 1 mole of carbon dioxide.

So,

Moles of C = 0.009157 moles

The molar mass of carbon is 12.0107 g/mol.

Carbon mass in molecule = 0.009157 x 12.0107 = 0.11 g

Since Valproic acid comprises only hydrogen, oxygen, and carbon, the oxygen mass in the sample = Total mass - Carbon mass - Hydrogen mass.

The sample's overall mass = 0.165 g.

Oxygen mass in the sample = 0.165 - 0.11 - 0.018588 = 0.036412 g

The molar mass of oxygen is 15.999 g/mol.

Moles of O = 0.036412 / 15.999 = 0.002276 moles

Taking the simplest ratio for H, O, and C yields:

0.01844: 0.002276: 0.009157

= 8: 1: 4

The empirical formula becomes $C_4H_8O$

While molecular formulas detail the precise count of atoms for each element, empirical formulas represent the simplest form or reduced ratio of these elements in the compound.

Consequently,

The molecular mass equals n × Empirical mass.

Here, n is a positive integer from 1, 2, 3...

Empirical mass = 4×12 + 8×1 + 16 = 72 g/mol.

Molar mass = 144 g/mol.

Thus,

The molecular mass = n × Empirical mass.

144 = n × 72

⇒ n = 2

The Valproic acid formula is = $C_8H_{16}O_2$