Percent by Mass

1
Percent by Mass

• 8/31

2
Law of Definite Proportions

• The mass of the compound is equal to the sum of
  the masses of the elements that make up the
  compound
• percent by mass -the ratio of the mass of each
  element to the total mass of the compound

3
Example

• A 134.50-g sample of aspirin is made up
• of 6.03 g of hydrogen, 80.70 g of carbon,
• and 47.77 g of oxygen. What is the
• percent by mass of each element in
• aspirin?
• -4.48 hydrogen, 60 carbon, 35.52 oxygen
• Does this add up to 100?

4
Find the percent by mass of

• Carbon in carbon dioxide
• Hydrogen in Water
• Oxygen in an oxygen molecule (O2)
• Each element in H2SO4