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How to Calculate the Percentage Composition of a Chemical Compound?
What is the percentage of the various elements in Sodium Carbonate [Na2CO3] ?
Given Atomic Weights: C = 12 ; O = 16 ; Na = 23
The first step is to calculate the Molecular Weight (or the Formula Weight) of the chemical compound by adding the atomic weights of the atoms (elements) that constitute the compound.
Molecular weight of Na2CO3
= (2 x Atomic weight of Na) + Atomic weight of C + (3 x Atomic weight of O)
= (2 x 23) + 12 + (3 x 16)
= 46 + 12 + 48 = 106
Now, 106 grams of Sodium Carbonate [Na2CO3] contain 46 grams of Sodium [Na], 12 grams of Carbon [C], and 48 grams of Oxygen [O].
Percentage of Sodium [Na] in Sodium Carbonate [Na2CO3] = 46/106 x 100 = 43.40%.
Percentage of Carbon [C] in Sodium Carbonate [Na2CO3] = 12/106 x 100 = 11.32%.
Percentage of Oxygen [O] in Sodium Carbonate [Na2CO3] = 48/106 x 100 = 45.28%.
Practice Exercise for Chemistry Module on Percentage Composition of Chemical Compounds