1. 6.6 THE COMPOSITION OF UNKNOWN COMPOUNDS

3. PERCENTAGE COMPOSITION - defined as the percentage, by mass, of each element in a compound In a 2.0g sample of a hydrocarbon, the mass of the carbon was determined to be 0.801g. What percentage of the hydrocarbon is carbon?

4. PERCENTAGE COMPOSITION If you calculated the percent composition of a 4.0g sample, what would be your answer? This is known as THE LAW OF DEFINITE PROPORTIONS!

5. To calculate percent composition, use the following formula: % element = m element m sample x 100%

6. EXAMPLE 1: A 500.00mg tablet of Aspirin, C 9 H 8 O 4 contains 300mg carbon and 8.08mg hydrogen. The remaining mass is oxygen. Determine its percent composition.

7. LET'S TAKE THIS A STEP FURTHER... Let's try to calculate percentage composition from a chemical formula.

8. EXAMPLE 2: Determine the percentage composition of calcium hydroxide, Ca(OH) 2

9. Learning check 1. What is the percentage composition of (NH 4 ) 3 PO 4 N: 28% H: 8%O: 43%P: 21%

10. HOMEWORK: Mole Airlines -due Wednesday Finish the Problem Set