Дано
m(ppa CHOH) 75 g
W(CHOH) = 40%
m практ(CHOOH) = 40 g
--------------------------
η-?
m(CHOH)= m(ppa CHOH)*W(CHOH) / 100% = 75*40%/100%= 30 g
M(CHOH) = 30 g/mol
n(CHOH)= m/M= 30 / 30 =1 mol
M(CHOOH) = 46 g/mol
n(CHOOH)= m/M= 40/46 = 0. 9 mol
n(CHOH)> n(CHOOH)
CHOH+Cu(OH)2 -->CHOOH+Cu+H2O
n(CHOH)= n(CHOOH) = 1 mol
m(CHOOH)= n*M= 1*46 = 46 g
η= m(практ)/m(теор) * 100% = 40/46*100% = 90%
ответ 90%