Answer
46.87% Fe
Work Step by Step
Mass % of an element= (Mass of that element in the compound÷Molar mass of the compound)×100
Here, Molar mass of Iron(II)Phosphate = (3× Atomic mass of Fe)+ (2×Atomic mass of P)+ (8× Atomic mass of O) = 357.48 g/mol
Mass of Fe= 3× Atomic mass of Fe= 167.535 g/mol.
Then, Mass percent of Fe = $\frac{167.535}{357.48}$×100= 46.87%