1)

дано

m(SO2) = 12.8 g

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m(O2)-?

S+O2-->SO2

M(SO2) = 64 g/mol

n(SO2) = m/M = 12.8 / 64 = 0.2 mol

n(S) = n(O2) = 0.2 mol

M(O2) = 32 g/mol

m(O2) = n*M = 0.2 * 32 = 6.4 g

ответ 6.4 г

2)

дано

m(P) = 6.2 g

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V(возд)-?

4P+5O2-->2P2O5

M(P) = 31 g/mol

n(P) = m/M = 6.2 / 31 = 0.2 mol

4n(P) = 5n(O2)

n(O2) = 5*0.2 / 4 = 0.25 mol

V(O2) = n*Vm = 0.25 * 22.4 = 5.6 L

V(возд) = V(O2) * 100% / 21% = 5.6 *100% / 21% = 26.67 L

ответ 26.67 л