Grade 12 Chemistry: Percentage Composition
A worksheet for Grade 12 Chemistry students covering the calculation of percentage composition from chemical formulas and experimental data.
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Grade 12 Chemistry: Percentage Composition
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Read each question carefully and provide detailed answers. Show all your work for calculations.
1. Which of the following best describes percentage composition?
The mass of each element in a compound.
The relative abundance of isotopes in an element.
The mass percent of each element in a compound.
The number of atoms of each element in a molecule.
2. What information is required to calculate the percentage composition of a compound?
Only the molar mass of the compound.
The atomic mass of each element and the total mass of the sample.
The chemical formula of the compound and the atomic mass of each element.
The density of the compound and its volume.
3. Percentage composition is defined as the of each element in a compound.
4. To find the percentage by mass of an element in a compound, you divide the total mass of the element in the compound by the of the compound and multiply by 100%.
5. Calculate the percentage composition of water (H₂O). (Atomic masses: H = 1.008 g/mol, O = 15.999 g/mol)
6. A 25.0 g sample of a compound contains 7.50 g of carbon, 1.25 g of hydrogen, and the rest is oxygen. Calculate the percentage composition of the compound.
7. The sum of the percentage compositions of all elements in a compound should always equal 100%.
True
False
8. Percentage composition can be used to determine the empirical formula of a compound.
True
False
9. A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. If the molar mass of the compound is 180.16 g/mol, determine its molecular formula. (Atomic masses: C = 12.011 g/mol, H = 1.008 g/mol, O = 15.999 g/mol)