дано
m(ppa NaOH) = 200 g
W(NaOH) = 8%
η(Fe(OH)3) = 80%
---------------------------
m пр.(Fe(OH)3)-?
m(NaOH) = 200 * 8% / 100% = 16 g
Fe2(SO4)3+6NaOH-->2Fe(OH)3+3Na2SO4
M(NaOH) = 40 g/moL
n(NaOH) = m/M =16 / 40 = 0.4 mol
6n(NaOH) = 2n(Fe(OH)3)
n(Fe(OH)3) = 2*0.4 / 6 = 0.133 mol
M(Fe(OH)3) = 107 g/mol
m теор.(Fe(OH)3) = n*M = 0.133 * 107 = 14.231g
m пр.(Fe(OH)3) = 14.231 * 80% / 100% = 11.4 g
ответ 11.4 г Д)