J.R. S. answered 02/16/21
Ph.D. University Professor with 10+ years Tutoring Experience
Fe = 55.85 g/mol
O = 15.999 g/mol
H = 1.008 g/mol
Iron(II) hydoxide = Fe(OH)2
molar mass Fe(OH)2 = 55.85 + (2*15.999) + (2*1.008) = 55.88 + 31.998 + 2.016 = 89.86 g/mol
Percent Fe = 55.85 / 89.86 (x100%) = 62.2% (3 sig. figs.)