дано
m(ppa BaSO4) = 30 g
W(BaSO4) = 5%
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m(Ba(OH)2)-?
m(BaSO4) = 30*5% / 100% = 1.5 g
BaSO4+2KOH-->Ba(OH)2↓+K2SO4
M(BaSO4)= 233 g/mol
n(BaSO4)= m/M= 1.5 / 233 = 0.006 mol
n(BaSO4)= n(Ba(OH)2) = 0.006 mol
M(Ba(OH)2)= 171 g/mol
m(Ba(OH)2)= n*M = 0.006 * 171 =1.026 g
ответ 1.026 г