А) 1) SO2+2H2S=(t)3S+2H2O
2) S+H2=(t)H2S
3) H2S+2NaOH=Na2S+2H2O
4) Na2S+3H2SO4=2NaHSO4+SO2+S+2H2O
б) 1) NaOH+H2SO4=NaHSO4+H2O
2) NaHSO4+NaOH=Na2SO4+H2O
3) Na2SO4+BaCl2=BaSO4+2NaCl
Mg(OH)2 = MgO + H2O
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СаСО3--->СаО+СО2. СО2+NaOH-->Na2CO3. Na2CO3+Mg(NO3)2--->MgCO3+2NaNO3
N(NO)=15/30=0.5 моль
V(NO)=0.5*22.4=11.2 л
N(NO)=0.5*6*10^23=3*10^23 шт