Since the compound contains 25.2% Hydrogen by mass and the compound is made of only carbon and hydrogen
Mass% of carbon = 100 - (mass% of hydrogen)
Mass% of carbon = 100 - 25.2
Mass% of carbon = 74.8%
Mass of each element in a given sample:
Let us take a 100 g sample of this compound
Since there is 25.2% hydrogen by mass, there is 25.2g hydrogen for every 100g of the compound
Similarly, there is 74.8 g carbon for every 100g of the compound
So, in a 100g sample:
Mass of Hydrogen = 25.2 grams
Mass of Carbon = 74.8 grams
Number of moles of each element in the 100g sample:
Moles of Carbon:
Molar mass of carbon = 12 g/mol
Number of moles = Given mass / molar mass
Number of moles = 74.8 grams / 12 g/mol
Moles of Carbon = 6.24 moles
Moles of Hydrogen:
Molar mass of Hydrogen = 1 g/mol
Number of moles = given mass / molar mass
Moles of Hydrogen = 25.2 / 1
Moles of Hydrogen = 25.2 moles
Empirical Formula:
The empirical formula of a compound is the simplest whole number ratio of the number of moles of the elements in the compound
Empirical formula = Moles of Carbon : Moles of Hydrogen
Empirical formula = 6.24 / 25.2
Since we need a whole number ratio, and these numbers don't simplify to be whole numbers. we will multiply both of them with a common number which will make them both whole
Multiplying both the numbers by 25 makes them whole
Empirical formula = 6.24 * 25 / 25.2 (25)
Empirical formula = 156 / 630
further simplifying the numbers, we can divide them both by 2
Empirical formula = 78 / 315
dividing these numbers by 3
Empirical formula = 16 / 105
Therefore, the ratios of the moles of carbon to the moles of Hydrogen in the empirical formula is: 16 : 105
Empirical formula = C16H105
