The mass of an adult bone is calculated from its average mass of about 11 kg and 50% of this mass is calculated to be calcium phosphate (Ca3(PO4)2)?

Here's how to calculate the mass of phosphorus in the bones:

Step 1: Calculate the total mass of calcium phosphate in the bones. The total bone mass is 11 kg, and 50% of this mass is calcium phosphate. $\text{Mass of Ca}_3(\text{PO}_4)_2 = 0.50 \times 11 \text{ kg} = 5.5 \text{ kg}$

Step 2: Determine the molar mass of calcium phosphate, Ca₃(PO₄)₂. Using approximate atomic masses: Ca = 40.08 g/mol, P = 30.97 g/mol, O = 16.00 g/mol. $\text{Molar mass of Ca}_3(\text{PO}_4)_2 = (3 \times 40.08) + (2 \times 30.97) + (8 \times 16.00)$ $\text{Molar mass of Ca}_3(\text{PO}_4)_2 = 120.24 + 61.94 + 128.00$ $\text{Molar mass of Ca}_3(\text{PO}_4)_2 = 310.18 \text{ g/mol}$

Step 3: Determine the total molar mass of phosphorus in one mole of Ca₃(PO₄)₂. There are 2 phosphorus atoms in each formula unit of Ca₃(PO₄)₂. $\text{Molar mass of P in Ca}_3(\text{PO}_4)_2 = 2 \times 30.97 \text{ g/mol} = 61.94 \text{ g/mol}$

Step 4: Calculate the mass of phosphorus in the bones. The mass of phosphorus is the fraction of phosphorus in calcium phosphate multiplied by the total mass of calcium phosphate. $\text{Mass of P} = \left( \frac{\text{Molar mass of P in Ca}_3(\text{PO}_4)_2}{\text{Molar mass of Ca}_3(\text{PO}_4)_2} \right) \times \text{Mass of Ca}_3(\text{PO}_4)_2$ $\text{Mass of P} = \left( \frac{61.94 \text{ g/mol}}{310.18 \text{ g/mol}} \right) \times 5.5 \text{ kg}$ $\text{Mass of P} \approx 0.19968 \times 5.5 \text{ kg}$ $\text{Mass of P} \approx 1.09824 \text{ kg}$ Rounding to two significant figures, consistent with the given values (11 kg, 50%): $\text{Mass of P} \approx 1.1 \text{ kg}$

The mass of phosphorus in the bones of an average adult is approximately $\boxed{\text{1.1 kg}}$.