1. Percentage Composition

2. Percentage composition
Indicates the relative amount of each element present in a compound.

3. Calculating percentage composition
Step 1 : Calculate molar mass
Step 2 : Divide the subtotal for each element’s mass by the molar mass.
Step 3: Multiply by 100 to convert to a percentage.

4. Example 1 1. Calculate the molar mass of water, H2O.
Step 1 – H- 2(1.01)= 2.02
O – 1(16.0)= 16.0
________
18.02

5. Step /18.02 X 100 = 11.21%
16.0 /18.02 X 100 = %
Water is composed of % hydrogen and % oxygen.

6. Example 2
Calculate the percentage composition of sucrose , C12H22O11.

7. Example 3
Find the percentage composition of hydrogen in sulfuric acid.

8. Your Turn: What is the percent composition of glucose (C6H12O6)
Step 1: figure out the molar mass:
Step 2: Divide the answer of each atom by the molar mass and multiply by 100

9. Practice Problems
Calculate the percentage composition by mass of the following compounds
1) HgO  
2) Na2S
3) (NH4)2S  
4) Sr(NO3)2