Percentage Composition

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# Percentage Composition - PowerPoint PPT Presentation

Percentage Composition. Recall that the FORMULA WEIGHT [or molar mass] of a substance is the MASS IN GRAMS of ONE MOLE of particles of that substance. One mole contains 6.022 X 10 23 particles. This number is called AVOGADRO’S NUMBER .

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## PowerPoint Slideshow about 'Percentage Composition' - derora

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### Percentage Composition

Recall that the FORMULA WEIGHT [or molar mass] of a substance is the MASS IN GRAMS of ONE MOLE of particles of that substance.

• One mole contains 6.022 X 1023particles.
• This number is called AVOGADRO’S NUMBER.

Within the mass of a mole of any compound, EACH ELEMENT contributes a CERTAIN PERCENTAGE to the OVERALL MASS.

• We can calculate these percentages. This is known as PERCENTAGE COMPOSITION.
Calculating Percentage Composition
• Calculating Percentage Composition is easy:
• 1. Find the FORMULA WEIGHT of the compound.
• 2. Calculate the MASS PERCENTAGE of EACH ELEMENT in the compound.
SAMPLE PROBLEM
• Calculate the Percentage Composition of Potassium Cyanide, KCN.
• 1. Find the FORMULA WEIGHT for KCN:
• 1 K X 39.098 g = 39.098 g
• 1 C X 12.011 g = 12.011 g
• 1 N X 14.007 g = 14.007 g
• Add Results  65.116 g/mol

Now we will use the data from EACH ELEMENT to find the Percentage Composition:

• 1 K X 39.098 g = 39.098g
• 1 C X 12.011 g = 12.011g
• 1 N X 14.007 g = 14.007 g
• 65.116 g/mol
• We will use the TOTAL MASS of EACH ELEMENT and divide it by the FORMULA WEIGHT, then MULTIPLY the results by 100%!

Mass of K

• %K = 39.098 g X 100% = 60.04% K
• 65.116 g/mol
• Formula Weight of KCN
• %C = 12.011 g X 100% = 18.45 % C
• 65.116 g/mol
• % N = 14.007 g X 100% = 21.51 % N
• 65.116 g/mol

Finally, CHECK YOUR MATH! Add all the PERCENTAGES together….they should be VERY CLOSE TO 100%!

• 60.04 % + 18.45% + 21.51% = 100%
PRACTICE PROBLEM
• Calculate the PERCENTAGE COMPOSITION of
• Calcium Carbonate, CaCO3.
• 1 Ca X 40.08 g = 40.08 g
• 1 C X 12.011 g = 12.011 g
• 3 O X 15.999 g = 47.997 g
• 100.088 g/mol

% Ca 40.08 g X 100% = 40.08% Ca

• 100.088 g/mol
• % C 12.011 g X 100% = 12.01% C
• 100.088 g/mol
• % O 47.997 g X 100% = 47.99% O
• 100.088 g/mol
• 40.08 % + 12.01% + 47.99% = 100.08% = 100%
• Find the Percentage Composition of Aluminum Phosphate, AlPO4.
• ___ Al x ______ g = ________g
• ___ P x ______ g = ________ g
• ___ O x ______ g = ________ g
• _______ g/mol

1 26.982 26.982

1 30.974 30.974

4 15.999 63.996

121.95

26.982 22.13

121.95

30.974 25.40

121.95

63.996 52.48

121.95

22.13 25.40 52.48 100.01

• % Al ________ x 100% = _______ %Al
• % P ________ x 100% = _______ %P
• % O ________ x 100% = ________ % O
• ____% Al + ____% P + ____ %O = _____%