Unformatted text preview: EXERCISE? Ca1CulatiOn of Percent Composition - Explanation: The percentage composition of a compound is the percentage by weight of each
element present. In the formula-of a compound, the subscript numbers represent the number of
. moles of atoms present in one mole of the compound. The percentage composition of any .
-' quantity bf the compound is the same as the percentage Composition of a single mole of the ' Compound. ' ' - Example: Calculate the percentage composition of potassium chlorate, KClO3. ‘ Solution:
_ Step 1: Calculate the molecular mass of the compound KC103. ‘
K =I .39g/mol" -
61 I = 35.5 g/mol
3 o u = .A37x1,6=848'g1m01-
1 Molecular = 122.5 g/mol
Mass - ‘ . Step2: Calculate percent of each element in the compound. Molar Weight ofK ‘ _ _ .39'g , %K = _ ‘ X100 .. = ,_ ,x100--=‘ 31.84%
- Molar weight of KC103 I 122.5 g
Molar weight of Cl ’ ' ' 35.5 g .
%C1 = X 100 = - X 100 = 28.98%
Molar weight of KClO3 122.5 g '
Molar weight of o ' 48 g . _
%O ' = ’ x100 = —.——_ x100 = 39.18%
Molar weight of KC1'03 , 122.5 g
Make sure the sum of all the percents = 100% 100.00% Hint: Round the percents to l or 2 decimal places for best accuracy. ...
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- Fall '11