# Calculations

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- Created by: Eleanor
- Created on: 27-04-13 14:38

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To calculate the Relative Formula Mass (Mr) you add up the Ar values

e.g. CO2 C=12 0=16 12 + 16x2 = 44

To calculate the Percentage Mass using the Mr:

Ar x Number of atoms divided by total Mr x 100

E.g. What is the percent of Carbon in CO2? Ar values C=14 O=16

14 divided by 44 x100 = 31.81%

To work out the formula of a compound:

E.g. I react 44.8g of Iron with 19.2g of Oxygen, what is the formula?

Fe O

44.8 19.2 (Mass given in question)

56 16 …

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