Test – Empirical and Molecular Formulas – 1

  1. A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. Calculate its empirical formula.

  2. A compound contains 60.0% carbon, 13.3% hydrogen, and 26.7% oxygen by mass. Calculate its empirical formula.

  3. A compound contains 3.0g of carbon, 0.5g of hydrogen, and 2.0g of oxygen. Calculate its empirical formula.

  4. A compound contains 2.4g of carbon, 0.6g of hydrogen, and 3.2g of oxygen. Calculate its empirical formula.

  5. Propane has the molecular formula C3H8. Complete the table below to calculate the relative molecular mass.

    Element Number of atoms Relative atomic mass Total mass contribution
    Carbon 3 12 ?
    Hydrogen 8 1 ?
    Relative molecular mass (Mr) ?

  6. Ethanol has the molecular formula C2H6O. Complete the table below to calculate the relative molecular mass.

    Element Number of atoms Relative atomic mass Total mass contribution
    Carbon 2 12 ?
    Hydrogen 6 1 ?
    Oxygen 1 16 ?
    Relative molecular mass (Mr) ?

  7. A compound has an empirical formula of CH3 and a relative molecular mass of 30. Determine its molecular formula.

  8. A compound has an empirical formula of C2H5O and a relative molecular mass of 90. Determine its molecular formula.

  9. A compound contains 85.7% carbon and 14.3% hydrogen by mass. Its relative molecular mass is 56. Determine its molecular formula.

  10. A compound contains 80.0% carbon and 20.0% hydrogen by mass. Its relative molecular mass is 30. Determine its molecular formula.

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