Final answer:
The mass percent of phosphorus in calcium phosphate (Ca3(PO4)2) is approximately 20%, calculated by finding the total mass of phosphorus in the formula, dividing by the total formula mass, and multiplying by 100.
Step-by-step explanation:
The chemical formula for calcium phosphate is Ca3(PO4)2. To calculate the mass percent of phosphorus in calcium phosphate, we must first determine the formula mass (also known as molar mass) of the compound. This involves adding together the atomic masses of each element present, multiplied by the number of atoms of that element in the formula.
Calcium's atomic mass is about 40.08 amu, phosphorus is about 30.97 amu, and oxygen is about 15.999 amu. So the formula mass of calcium phosphate would be calculated as follows:
- (3 atoms of Ca) × 40.08 amu = 120.24 amu
- (2 atoms of P) × 30.97 amu = 61.94 amu
- (8 atoms of O) × 15.999 amu = 127.992 amu
Adding these together gives us a total formula mass for calcium phosphate of:
120.24 amu + 61.94 amu + 127.992 amu = 310.172 amu
To find the mass percent of phosphorus, we then divide the total mass of phosphorus by the total formula mass, and multiply by 100:
(61.94 amu / 310.172 amu) × 100 = 19.96%
Therefore, the mass percent of phosphorus in calcium phosphate is approximately 20%, when rounded to the nearest percentage.