Half Reactions / net ionic equation

hey

Write half-reactions for the following chemical equation, and determine the overall or net ionic equation.

 

a) Zn(s) + Cl2(g) -> ZnCl2(s)

 

 

 

b) Fe2O3(s) + 2Al(s) -> 2Fe(s) + Al2O3(s)

 

 

PLEASE HELP

Zn + 2e- --- > Zn

Cl+ 2e- ----> 2Cl-

Zn(s) + Cl2(g) -> ZnCl2(s)

b) Fe2O3(s) + 2Al(s) -> 2Fe(s) + Al2O3(s)

in Fe2O3 - Fe is +3 and O is -2

in Al = 0

in Fe = 0

in Al2O3 = Al is +3 and O is-2

so, Al is changing its oxidation state from 0 to +3

and Fe is changing its oxidation state from 0 to -2   

                 Fe 3+ + 3 e-  →Fe  reduction half

               Al3+   + 3 e- -----> Al  oxidation half

Fe2O3(s) + 2Al(s) -> 2Fe(s) + Al2O3(s)  overall and net reaction since all the components are in solid state it wont dissociate into ions..

a) Zn(s) + Cl2(g) -> ZnCl2(s)

Half reactions are reduction and oxidation here 

Zn(s) -> Zn2+(s)  +2e-         (Oxidation)

2e- + Cl2(g) ->2Cl-(s)   ( Reduction)

Overall 

 Zn(s) + Cl2(g) -> ZnCl2(s)

 

 

b) Fe2O3(s) + 2Al(s) -> 2Fe(s) + Al2O3(s)

 

 

  6H+ +  6e-  +  Fe2O3(s) -> 2Fe(s)  +   3H2O

 

       3H2O+    2Al(s) ->  Al2O3(s) +6e- +  6H+ 

 

Overall 

Fe2O3(s) + 2Al(s) -> 2Fe(s) + Al2O3(s)