GCE O Level Chemistry : Moles and Empirical Formulae

Moles And Formulae: Empirical Formulae

The Formulae of a Chemical Compound Tells you how many atoms of one element are joined with the atoms of other elements. Take the e.g of water in which 2 Hydrogen atoms are joined to 1 Oxygen atom therefore the formulae of water is H2O.

We can use moles to calculate the empirical formulae of a molecule.

Example

2g of Hydrogen was found to join with 16g of Oxygen to form water. What is the Empirical Formulae of Water.

We will first Calculate the moles of Hydrogen present in 2g and Number of moles of Oxygen present in 16g.

If you do not know How to calculate Moles See The post Stoichiometry and the mole Concept by

Clicking Here 

number of moles of Hydrogen atom in 2g=2

number of moles of Oxygen atom in 16g=1

Now we have the simple Ratio that is 2 moles of Hydrogen Join with 1 mole of oxygen.

Thus the Empirical Formulae Will be H2O

Now Try Solving The Question below

Q) 112g of Calcium Oxide joined with 88g of Carbon dioxide to form Calcium Carbonate. What is The empirical formulae of Calcium Carbonate.

Hint: You have to Find Number of moles here by using Molecular mass not atomic mass as to molecules have joined together not atoms.

The simplest ratio will be 1 to 1. See if you got it right.

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