Empirical and Molecular Formulas Practice
1. What is the percentage composition of Na₂SO₄?
Molar Mass of Na₂SO₄
= ( 2 x 22.990 ) + ( 1 x 32.066 ) + ( 4 x 15.999 )
= 142.042 g/mol
Percentage Composition:
% Na = ( 2 x 22.990 ) / 142.042 = 32.37%
% S = ( 1 x 32.066 ) / 142.042 = 22.58%
% O = ( 4 x 15.999 ) / 142.042 = 45.05%
∴ Sodium sulfate (Na₂SO₄) is 32.37% sodium (Na), 22.58% sulphur (S) and
45.05% oxygen (O).
2. What is the percentage composition of propane, C₃H₈?
Molar Mass of C₃H₈
= ( 3 x 12.011 ) + ( 8 x 1.008 )
= 44.097 g/mol
Percentage Composition:
% C = ( 3 x 12.011 ) / 44.097 = 81.71%
% H = ( 8 x 1.008 ) / 44.097 = 18.29%
∴ Propane (C₃H₈) is 81.71% carbon (C) and 18.29% hydrogen (H).
1. What is the percentage composition of Na₂SO₄?
Molar Mass of Na₂SO₄
= ( 2 x 22.990 ) + ( 1 x 32.066 ) + ( 4 x 15.999 )
= 142.042 g/mol
Percentage Composition:
% Na = ( 2 x 22.990 ) / 142.042 = 32.37%
% S = ( 1 x 32.066 ) / 142.042 = 22.58%
% O = ( 4 x 15.999 ) / 142.042 = 45.05%
∴ Sodium sulfate (Na₂SO₄) is 32.37% sodium (Na), 22.58% sulphur (S) and
45.05% oxygen (O).
2. What is the percentage composition of propane, C₃H₈?
Molar Mass of C₃H₈
= ( 3 x 12.011 ) + ( 8 x 1.008 )
= 44.097 g/mol
Percentage Composition:
% C = ( 3 x 12.011 ) / 44.097 = 81.71%
% H = ( 8 x 1.008 ) / 44.097 = 18.29%
∴ Propane (C₃H₈) is 81.71% carbon (C) and 18.29% hydrogen (H).
