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 elements 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, H 2 O. Step 1 – H- 2(1.01)= 2.02 O – 1(16.0)= 16.0 ________ 18.02

5. Step 2 2.02/18.02 X 100 = 11.21% 16.0 /18.02 X 100 = 88.79 % Water is composed of 11.21 % hydrogen and 88.79 % oxygen.

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

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