Fe(oh)3 ® fe2o3 ® fecl3 ® fe(oh)3 ® fe2o3 ca -cao - ca(oh)2 - caco3 - cao zn ® zno ® zncl2 ® zn(oh)2 ® zno

2Fe(OH)3 = Fe2O3 + 3H2O
 FeCl3 + 3 NaOH = Fe(OH)3  +3 NaCl
       2Fe(OH)3  =Fe2 O3  + 3H2O
Ca + O2 = CaO
CaO + H2O =- Ca(OH)2
Ca(OH)2  + CO2  = CaCO3  + H2O
CaCO3  = CaO + H2O
2Zn +O2= 2ZnO
ZnO + 2HCl = ZnCl2 +H2O
ZnCl2  + 2NaOH = Zn(OH)2 + 2NaCl
Zn(OH)2 = ZnO +H2O