Question

Determine the correct empirical formula of a compound containing 26.68% carbon, 2.24% hydrogen and 71.08% oxygen?

Answer 1

• For calculating the empirical formula we always assume a total of 100g so that we have

            26.68 grams of carbon

            2.24 grams of hydrogen and

            71.08 grams of oxygen

• The next step is to convert the grams to moles using the molar masses of the compounds
  Carbon = 12 g/mol
  Hydrogen = 1.001g/mol
  Oxygen = 16 g/mol
• Moles of carbon = 26.68 g /12 g mol-1which gives 2.22 moles
  Moles of Hydrogen = 2.24 g /1.001 g mol-1which gives 2.24 moles
  Moles of Oxygen = 71.08 g /16g mol-1which gives 4.44 moles
• Then, divide all the values by the fewest number of moles we find out how much of each is in the empirical formula, so divide everything by 2.22.
  2.22/2.22 = 1 C
  2.24/2.22 = ~1 H
  4.44/2.22 = 2 O
• So the empirical formula is CHO2