Question

An organic compound contains carbon hydrogen and oxygen. If it contains 45.27% carbon and 4.43 % hydrogen by mass determine the empirical formula

Answer 1

This organic compound has in its structure the next element: C, H, and O

45.27% C

4.43 % H

The rest 100%-45.27%-4.43 = 50.3 % O

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The empirical formula of a chemical compound is the simplest whole-number ratio of atoms present in a compound.

Procedure:

Step 1)

We convert % into grams (g). Let's assume we have a 100g sample. Therefore,

45.27 % C = 45.27 g

4.43 % H = 4.43 g

50.3 % O = 50.3 g

Step 2)

We calculate the number of moles of each element. To do this, we need every atomic mass

For C)

`45.27\text{ g x }\frac{1\text{ mol}}{12.01\text{ g}}=3.767\text{ moles}`

For H)

`4.43\text{ g x }\frac{1\text{ mol}}{1.00\text{ g}}=\text{ 4.43 moles}`

For O)

`50.3\text{ g x }\frac{1\text{ mol}}{16.0\text{ g}}=3.14\text{ moles}`

Step 3)

We divide all moles by the smallest one of them (3.14 moles of O)

For C) 3.767 moles/3.14 moles = 1.19 = 1 (we need integer numbers)

For H) 4.43 moles/3.14 moles = 1.41 = 1

For O) 3.14 moles/3.14moles = 1

The empirical formula is CHO