дано
m(V2O5) = 455 g
m(Ca) = 600 g
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m(V)-?
M(V2O5) = 182 g/mol
n(V2O5) = m/M = 455 / 182 = 2.5 mol
M(Ca) = 40 g/mol
n(Ca) = m/M = 600 / 40 = 15 mol
n(V2O5) < n(Ca)
V2O5+5Ca-->5CaO+2V
n(V2O5) = 2n(V)
n(V) = 2*2.5 = 5 mol
M(V) = 51 g/mol
m(V) = n*M = 5*51 = 255 g
ответ 255 г