Question

An adult's bone weight about 11kg, 50% of mass is ca3(po4)-calcium phosphate. what is mass of phosphorus in the bone of the average adult??

Answer 1

Given:

                          Mass of Ca₃(PO₄)₂ = 50% of 11 kg = (50*11)/100 = 5.5 kg = 5.5*1000 =5500 g

                          Molecular Mass of Ca₃(PO₄)₂ = (3*40)+(2*31)+(8*16)= 310 g/mole

                         From this, Number of moles of Ca₃(PO₄)₂ = weight/ molecular mass = 5500/310 = 17.74 moles

          % of P in Ca₃(PO₄)₂ = (Atomic mass of P * No.of atoms in the formula)*100/Molecular weight of Ca₃(PO₄)₂

                                                      =2*31*100/310 = 20%

                           So, mass of P in 5.5 kg of Ca₃(PO₄)₂ = 5.5*20/100 = 1.1 kg =1100 g

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