дано
m(ppa H2SO4) =200 g
W(H2SO4) = 9.8 %
m(ppa KOH) = 400 g
w(KOH) = 7%
--------------------------
m(K2SO4)-?
m(H2SO4) = 200 * 9.8% / 100% = 19.6 g
M(H2SO4) = 98 g/mol
n(H2SO4) = m/M = 19.6 / 98 = 0.2 mol
m(KOH) = 400*7% / 100% = 28 g
M(KOH) = 56 g/mol
n(KOH) = m/M = 28 / 56 = 0.5 mol
n(H2SO4) < n(KOH)
H2SO4+2KOH-->K2SO4+2H2O
n(H2SO4) = n(K2SO4) = 0.2 mol
M(K2SO4) = 174 g/mol
m(K2SO4) = n*M = 0.2*174 = 34.8 g
ответ 34.8 г