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Percent Composition

Today we’ll be using our Homework from last night (Molar Mass Worksheet) to determine the Percent Composition of different atoms in those molecules. It’s really easy see the example below to help you with today’s assignment. The Answer key can be found on the Docs page. Use this as a tool to check work, not to copy.

Molar Mass: CaCl2 %Composition: CaCl2
1 CaCl2 Molecule:
1 Ca  = 1 x 40.1 = 40.1
2 Cl
2 = 2 x 35.5 = 71.0
                            111.1g/mole
%Ca= (40.1/111.1) x 100 = 36.1%Ca
%Cl= (71.0/111.1) x 100 = 63.9%Cl