To determine the percent composition of calcium in calcium chloride (CaCl2), we follow these steps:
1. Identify the molar masses from the periodic table:
- Calcium (Ca) has a molar mass of 40.08 g/mol.
- Chlorine (Cl) has a molar mass of 35.45 g/mol.
2. Calculate the molar mass of calcium chloride (CaCl2):
- Calcium chloride consists of one calcium atom and two chlorine atoms.
- The molar mass of calcium chloride can be calculated by adding the molar mass of one calcium atom and the molar masses of two chlorine atoms:
- Molar mass of CaCl2 = Molar mass of Ca + 2 Molar mass of Cl
- Molar mass of CaCl2 = 40.08 g/mol + 2 35.45 g/mol
3. Perform the arithmetic:
- Molar mass of CaCl2 = 40.08 g/mol + 2 35.45 g/mol
- Molar mass of CaCl2 = 40.08 g/mol + 70.90 g/mol
- Molar mass of CaCl2 = 110.98 g/mol
4. Calculate the percent composition of calcium:
- The percent composition of calcium is determined by the ratio of the molar mass of calcium to the molar mass of calcium chloride, multiplied by 100 to convert it to a percentage.
- Percent composition of Ca = (Molar mass of Ca / Molar mass of CaCl2) 100
- Percent composition of Ca = (40.08 g/mol / 110.98 g/mol) 100
5. Calculate and round the result:
- Percent composition of Ca ≈ 0.3610 100
- Percent composition of Ca ≈ 36.10%
- Rounding to the nearest whole percent gives us 36%.
Therefore, the percent composition of calcium in calcium chloride (CaCl2) is 36%.
