21.0g12.5g 21.0g-14.8g=6.2gCO2H2Om(NaHCO3)=1686.2g62=16.8gm(Na2CO3)=21.0g-16.8g=4.2g,20%KClKBr3.87gAgNO36.63gA.0.241 B.0.259 C.0.403 D.0.4871. 0.4g CO CO20.75g A. FeO B. Fe2O3 C. Fe3O4 D. Fe4O5 CaCO3n(O)=n(CaCO3)=0.0075mol m(O)=0.0075mol16g/mol=0.12gm(Fe)=0.4g-0.12g=0.28gn(Fe)=0.005moln(Fe)n(O)=2:3B2. 100mL7mol?LD10.56LFe2+Fe3+ A. 72.4% B. 71.4% C. 79.0% D. 63.6% 3. 8g Fe2O3150mL7g1.68L H2FeFe2O34mol/LNaOH150mL A. 1.5mol/L B. 0.5mol/L C. 2mol/L D. 1.2mol/L 4. 5.6gNO3.2gFe2+Fe3+ A. 41 B. 21 C. 11 D. 32 28.4g1mol/L500mLA.35g B.30 g C.20 g D.15 g4FeS2+11O22Fe2O3+8SO22SO2+O22SO3SO3+H2O=H2SO42.5t85FeS2FeS2S5.098 FeS22SO22SO32H2SO4 FeS2H2SO4FeS2SH2SO4SFeS22H2SO49898x2x2.5tx85%x(1-5.0%)/120x98%=3.36t1230.103 gP2Mo24O773.60 1030.504 g31.0