`27)` `2Al(OH)_3 + 3H_2SO_4 -> Al_2(SO_4)_3 + 6H_2O`

`28)` `Cu(OH)_2 + H_2SO_4 -> CuSO_4 + 2H_2O`

`29)` `Fe(OH)_3 + 3HCl -> FeCl_3 + 3H_2O`

`30)` `C_3H_4 + 4O_2 -> 3CO_2 + 2H_2O`

`31)` `SO_2 + 2H_2S -> 3S downarrow + 2H_2O`

`32)` `FeS + 2HCl -> FeCl_2 + H_2S uparrow`

`33)` `Fe_2O_3 + 3H_2 -> 2Fe + 3H_2O`

`34)` `Fe_3O_4 + 4H_2 -> 3Fe + 4H_2O`

`35)` `2Fe_2O_3 + 3C -> 4Fe + 3CO_2`

27) $2Al(OH)_{3}+3H_{2}SO_{4}$ $\longrightarrow$ $Al_{2}(SO_{4})_{3}+6H_{2}O$ 

28) $Cu(OH)_{2}+H_{2}SO_{4}$ $\longrightarrow$ $CuSO_{4}+2H_{2}O$  

29) $Fe(OH)_{3}+3HCl$ $\longrightarrow$ $FeCl_{3}+3H_{2}O$ 

30) $C_{3}H_{4}+4O_{2}$ $\xrightarrow{t^{o}}$ $3CO_{2}+2H_{2}O$ 

31) $SO_{2}+2H_{2}S$ $\longrightarrow$ $3S_{↓}+2H_{2}O$ 

32) $FeS+2HCl$ $\longrightarrow$ $FeCl_{2}+H_{2}S_{\uparrow}$ 

33) $Fe_{2}O_{3}+3H_{2}$ $\xrightarrow{t^{o}}$ $2Fe+3H_{2}O$ 

34) $Fe_{3}O_{4}+4H_{2}$ $\longrightarrow$ $3Fe+4H_{2}O$ 

35) $2Fe_{2}O_{3}+3C$ $\xrightarrow{t^{o}}$ $4Fe+3CO_{2}$