Question

A sample of a compound contains 160 g of oxygen and 20.2 g of hydrogen. Give the compound's empirical formula.

Answer 1

Answer : The empirical formula of a compound is, $H_2O_1$

Solution : Given,

Mass of O = 160 g

Mass of H = 20.2 g

Molar mass of O = 16 g/mole

Molar mass of H = 1 g/mole

Step 1 : convert the given masses into moles.

Moles of O = $\frac{\text{ given mass of O}}{\text{ molar mass of O}}= \frac{160g}{16g/mole}=10moles$

Moles of H = $\frac{\text{ given mass of H}}{\text{ molar mass of H}}= \frac{20.2g}{1g/mole}=20.2moles$

Step 2 : For the mole ratio, divide each value of the moles by the smallest number of moles calculated.

For O = $\frac{10}{10}=1$

For H = $\frac{20.2}{10}=2.02\approx 2$

The ratio of O : H = 1 : 2

The mole ratio of the element is represented by subscripts in empirical formula.

The Empirical formula = $H_2O_1$

Therefore, the empirical formula of a compound is, $H_2O_1$

Answer 2

Amount of oxygen in the compound = 160 g
Amount of oxygen in the compound = 20.2 gm
Mole of oxygen in the compound = 160/16
                                                     = 10 moles
Mole of hydrogen in the compound = 20.2/1.01
                                                         = 20 moles
Then
The ratio of oxygen to ration of hydrogen = 1:2
So
The empirical formula of the compound is H2O. I hope the answer has come to your help.