# Empirical Formulae

How to work out the Empirical Formulae

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• Created by: Jodie
• Created on: 09-11-11 19:17

## Empirical Formulae

Empirical Formulae - the simplest whole number ratio of atoms of each element present in a compound

To work out the Empirical formulae split the answer up into 4 parts:

Mass/percentage composition(%)

Mr

Moles

Ratio

First work out the moles, by doing Mass(or %)/Mr.

Then work out the ratio, by dividing all of the ratios by the smallest ratios. You then need to make all the ratios integers if they are not already, by timesing or dividing.

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## Example

Nitram is an ammonium fertiliser: it is 35% nitrogen, 5% hydrogen and 60% oxygen. Calculate its empirical formular.

Nitrogen                Hydrogen                     Oxygen

Mass      35                          5                                  60

Mr          14                          1                                  16

Moles    2.5                          5                                  3.75

Ratio     1                             2                                  1.5

Whole    2                            4                                   3

number ratio (Final ratio needs to be in interger form)

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