The percentage composition of a compound is determined by calculating the ratio of the mass of each element to the total mass of the compound and then multiplying by 100.
Here's a breakdown of the process:
Understanding Percentage Composition
Percentage composition tells us the proportion of each element present in a compound, expressed as a percentage. This is useful for understanding the makeup of a substance. According to the provided reference, "the percentage composition of a given compound is defined as the ratio of the amount of each element to the total amount of individual elements present in the compound multiplied by 100." Essentially, it's about finding out the mass contribution of each element within the total mass of the compound.
Steps to Determine Percentage Composition
Here’s a step-by-step process, as informed by the reference:
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Determine the Molar Mass of the Compound:
- Find the atomic masses of each element in the compound from the periodic table.
- Multiply the atomic mass of each element by its subscript in the chemical formula.
- Add these values together to find the total molar mass of the compound.
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Calculate the Mass of Each Element:
- Using the same atomic masses and subscripts from step one, calculate the total mass of each individual element in one mole of the compound.
- For example, in H₂O, the mass of hydrogen would be 2 x the atomic mass of hydrogen, and the mass of oxygen would be 1 x the atomic mass of oxygen.
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Calculate the Percentage:
- For each element, divide its mass by the total molar mass of the compound (determined in step 1).
- Multiply the result by 100 to express it as a percentage.
**Percent Composition Formula**
`% of element = (mass of element in 1 mole of compound / molar mass of compound) x 100`Example: Calculating Percentage Composition of Water (H₂O)
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Molar Mass of H₂O:
- Hydrogen (H) atomic mass ≈ 1 g/mol
- Oxygen (O) atomic mass ≈ 16 g/mol
- Molar mass of H₂O = (2 x 1 g/mol) + (1 x 16 g/mol) = 18 g/mol
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Mass of Each Element in One Mole of H₂O:
- Mass of Hydrogen (2H) = 2 g
- Mass of Oxygen (1O) = 16 g
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Calculating Percentages:
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Percentage of Hydrogen = (2 g / 18 g) x 100 ≈ 11.11%
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Percentage of Oxygen = (16 g / 18 g) x 100 ≈ 88.89%
Therefore, water is approximately 11.11% hydrogen and 88.89% oxygen by mass.
Significance of Percentage Composition
Knowing the percentage composition is crucial in several contexts:
- Identifying Unknown Compounds: By comparing the experimentally determined percentage composition with known compound data, you can determine the identity of a compound.
- Quality Control: It helps ensure that a manufactured compound contains the correct proportions of each element.
- Stoichiometry: Percentage composition is used in stoichiometric calculations in chemistry.
