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How to Calculate the Mass Percent Composition of Each Constituent Element of Sulfuric Acid

Sulfuric acid is an inorganic acid with the chemical formula H2SO4. This compound is a strong acid and is widely used in laboratory and industry. Calculating percent composition of a compound is a common class assignment in chemistry. To accomplish this task, first you need to compute the molecular weight of the acid taking into account that it consists of three elements: hydrogen (H), sulfur (S) and oxygen (O).

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Instructions

- 1
  Obtain atomic masses of all elements that compose the H2SO4 molecule using the periodic table of elements. The atomic weights of hydrogen (H), sulfur (S) and oxygen (O) are 1, 32 and 16, respectively.
- 2
  Multiply the atomic weight of hydrogen by the number of the atoms (two) in the molecule to calculate the mass contributions of hydrogen: 1 x 2 = 2.
- 3
  Multiply the atomic weight of sulfur by the number of the atoms (one) in the molecule to calculate the mass contributions of hydrogen: 32 x 1 = 32.
- 4
  Multiply the atomic weight of oxygen by the number of the atoms (four) in the molecule to calculate the mass contributions of hydrogen: 16 x 4 = 64.
- 5
  Add up all masses of all elements to calculate the molecular weight of sulfuric acid: 2 + 32 + 64 = 98.
- 6
  Divide the mass contribution of hydrogen by the molecular weight of sulfuric acid, and then multiply by 100 to calculate the percent of hydrogen: (2 / 98) x 100 = 2.0 percent
- 7
  Divide the mass contribution of sulfur by the molecular weight of sulfuric acid, and then multiply the result by 100 to calculate the percent of sulfur: (32 / 98) x 100 = 32.7 percent.
- 8
  Divide the mass contribution of oxygen by the molecular weight of sulfuric acid, and then multiply the result by 100 to calculate the percent of oxygen: (64 / 98) x 100 = 65.3 percent.

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