дано
m(ppa H2SO4) = 500 g
W(H2SO4) = 40%
CaO
----------------------
m(CaSO4)-?
m(H2SO4) = 500*40% / 100% = 200 g
H2SO4+CaO-->CaSO4+H2O
M(H2SO4) = 98 g/mol
n(H2SO4) = m/M = 200 / 98 = 2.04 mol
n(H2SO4)= n(CaSO4) = 2.04 mol
M(CaSO4) = 136 g/mol
m(CaSO4) = n*M = 2.04*136 = 277.44 g
ответ 277.44 г