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1) HCl + NaNO3 = HNO3 + NaCl
H(+)+ Cl(-)+Na(+) +NO3(-) = H(+)+NO3(-) + Na(+) + Cl(-)
2) CuSO4 + Na2S = CuS + Na2SO4
Cu(+2) + SO4(-2) + 2Na(+) +S(-2) = CuS + 2Na(+) + SO4 (-2)
Cu(+2) + S(-2) = CuS
3) Pb(NO3)2 + 2NaCl = PbCl2 + 2NaNO3
Pb(+2) + 2NO3(-) + 2Na(+) + 2Cl(-) =PbCl2 + 2Na(+) + 2NO3(-)
Pb(+2) + 2Cl(-) = PbCl2
4)CaBr2 + H2CO3 = CaCO3 + 2HBr
Ca(+2) +2Br(-) + CO2 + H2O = CaCO3 + 2H(+) + 2Br(-)
Ca(+2) + CO2 + H2O = CaCO3 +2H(+)
5) 3Ca(OH)2 +2 H3PO4 = Ca3(PO4)2 +6 H2O
3Ca(OH)2 + 6H(+) + 2PO4(-3) = Ca3(PO4)2 + 6H2O
M(Al) = 27 г/моль
m(Al) = (21,4 л * 27 г/моль * 2 моль) : (22,4 л/моль * 3 моль) = 17,2 г - масса чистого алюминия, вступившего в реакцию
w%(примеси) = (18 г - 17,2 г) : 18 г * 100 % = 4,44 %