1. Thursday, January 24, 2013 Percent Composition

2. Students will be able to: Calculate the percent composition of chemical compounds.

3. The percent composition tells us the % by mass of each type of element in a compound. To find % comp by mass, you take the mass of the element in the compound and divide by the total mass of the compound

4. the percentage by mass of each element in a compound

5. First Determine molar mass of Cu 2 S Cu: 2x 63.5 = 127 S: 1 x 32 = 32mass = 159g/mol Find the % composition of Cu 2 S. %Cu = 2*63.5 g Cu 159 g Cu 2 S  100 = 79.8% Cu  100 = %S = 32 g S 159 g Cu 2 S 20.2% S

6. How many grams of copper are in a 38.0-gram sample of Cu 2 S? (38.0 g Cu 2 S)(0.798) = 30.3 g Cu Cu 2 S is 79.8% Cu

7.  100 = %H 2 O = 36.0 g 147.0 g 24.5% H 2 O Find the mass percentage of water in calcium chloride dihydrate, CaCl 2 2H 2 O?

8. Determine the percent composition of Mn(SO 4 ) 2. How many grams of manganese are in a 500g sample of Mn(SO 4 ) 2 ? What percent of PO 5 is phosphorous?