1. Find the molar mass of Ca(OH)₂:
* Calcium (Ca): 40.08 g/mol
* Oxygen (O): 16.00 g/mol (x 2 = 32.00 g/mol)
* Hydrogen (H): 1.01 g/mol (x 2 = 2.02 g/mol)
Total molar mass = 40.08 + 32.00 + 2.02 = 74.10 g/mol
2. Calculate the mass of oxygen in one mole of Ca(OH)₂:
* Mass of oxygen = 32.00 g/mol
3. Divide the mass of oxygen by the total molar mass and multiply by 100%:
* (32.00 g/mol / 74.10 g/mol) x 100% = 43.18%
Therefore, the percent by mass of oxygen in Ca(OH)₂ is 43.18%.
