1)
дано
M(Fe2O3) = 56*2+16*3 = 160 g/mol
W(Fe) = 56*2 / 160 * 100% = 70%
W(O) = 16*3 / 160 * 100% = 30%
2)
дано
m(ppaZn(NO3)2) = 50 g
W = 8%
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m(Zn(NO3)2)-?
V(H2O)-?
m(Zn(NO3)2) = 50*8% / 100% = 4 g
m(H2O) = 50 - 4 = 46 g
V(H2O) = m(H2O) / p(H2O) = 46 / 1 = 46 mL
ответ 4 г, 46 мл
3)
дано
V(возд) = 300 L
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m(O2)-?
V(O2) = 300*21% / 100% = 63 L
M(O2) = 32 g/mol
m(O2) = M(O2) * V(O2) / Vm = 32*63 / 22,4 = 90 g
ответ 90 г