Question

1. Calculate the empirical and molecular formula of a hydrocarbon, which is found to
contain 14.3% hydrogen and 85.7% carbon. If molecular mass of the hydrocarbon is 28​

Answer 1

Explanation:

This is worked out by the ratios of the carbon to the hydrogen.

Assume 100 g of compound.

Therefore in these 100 grams there are 85.7 g of carbon and 14.3 g of hydrogen.

Converting to mole ratios.

Carbon : Hydrogen

85.7/12 : 14.3/1

7.14 : 14.3

1 : 2

This is the empirical formula of the chemical ratio : i.e. CH2 which is the simplest ratio of elements.

If the molar mass of the above sample is known (in this case 28) then it is possible to work out a molecular formula of (CH2) x n = 28. Therefore n would have a value of 2.