MGCCC, Perk Learning Lab

Created by TLM

 

BALANCING RED-OX EQUATIONS

 

1.      Write the basic equation.

2.      Assign oxidation numbers to everything in the equation.

3.      Identify what was oxidized and what was reduced.

 

OXIDATION

REDUCTION

Charge goes up

Charge goes down

Losses electrons

Gains electrons

Gains oxygen

Losses oxygen

Losses hydrogen

Gains hydrogen

 

4.      Write an equation for the oxidized substance and an equation for the reduced substance.

5.      Indicate in the equation in “4” how many electrons were lost in oxidation and how many electrons were gained in reduction.

6.      Use a least common multiple in order to get the number of electrons gained and lost to be equal.

7.      Enter the coefficients from “6” back into the original equation from “1”.

8.      Balance the REMAINING elements by inspection.

 

 

EXAMPLE:

 

Cu + HNO3                 Cu(NO3)2 + NO2 + H2O

 

Cu 0 + H+1N+5O3-2                  Cu+2(N+5O3-2)2 + N+4O2+2 + H2+1O-2

 

Copper is oxidized; Nitrogen is reduced

 

OX: Cu 0               Cu+2                                   RED:  N+5                   N+4

            0e-            +2e-                                                 +5e-                 +4e-

            total difference is 2 e-                                       total difference is 1e-

        Cu 0 – 2e-                 Cu+2                                     N+5  + 1e-              N+4

                                                            Multiply by 2 to equalize electrons lost and gained

 (OX already has 2e-)                                                   2N+5 +2e-                2N+4

 

COMBINE: Cu 0 + 2N+5             Cu+2 + 2N+4

 

Enter Coefficients:   Cu + 2HNO3                     Cu(NO3)2 + 2NO2 + H2O

 

Balance by Inspection: Cu + 4HNO3                Cu(NO3)2 + 2NO2 + 2H2O