Final answer:
The percent composition of calcium in CaO is calculated by dividing the atomic mass of calcium by the molar mass of CaO and multiplying by 100%, which equals 71.5%.
Step-by-step explanation:
The question asks for the percent composition of calcium (Ca) in calcium oxide (CaO). To calculate this, we start by finding the atomic masses of the constituent elements from the periodic table. Calcium has a molar mass of 40.078 g/mol and oxygen has a molar mass of 15.999 g/mol. The molar mass of CaO is the sum of the molar masses of calcium and oxygen, which is 40.078 g/mol + 15.999 g/mol = 56.077 g/mol for CaO.
Next, to find the percent composition of calcium in CaO, we take the mass of calcium (40.078 g/mol) and divide it by the molar mass of CaO (56.077 g/mol), then multiply by 100%.
Percentage composition of Ca in CaO: (40.078 g/mol / 56.077 g/mol) x 100% = 71.5%.
Therefore, the correct option is:
- Option A: 40.078 g / 56.077 g x 100%