Lecture 20.3- Balancing Redox

Balancing redox reactions Read the 5 steps for balancing redox equations using the half-reaction method. You will get the steps on the test, but you must know what they mean in order to use them.

Balance the equation MnO 4 - + Fe 2+  Fe 3+ + Mn 2+ ,[object Object],[object Object],[object Object],Each ½ reaction contains a reactant and a product that “look the same”

STEP 2- balance each ½ reaction using steps 2a-2d ,[object Object],[object Object],[object Object],+ 4 H 2 O 2c- balance hydrogen using H + There are 8 H on the right, add 8H + on the left 2d- balance the charge using electrons The total charge is +7 on the left and +2 on the right, add 5e - to the left giving both sides a charge of +2. 5e - + 8H + +

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],STEP 2- balance each ½ reaction using steps 2a-2d + e - +2 = +3 + (-1)

STEP 3- The 1/2 reactions must have the same number of e - If necessary, multiply one or both 1/2 reactions to make the number of electrons even. ,[object Object],[object Object],[object Object],[object Object],[object Object],5 5 5

STEP 4- add the ½ reactions together and cancel out anything that appears on both sides ,[object Object],[object Object],[object Object],The electrons will always cancel out 8H + + MnO 4 - + 5Fe 2+  Mn 2+ + 4H 2 O + 5Fe 3+

STEP 5 – check that elements and charges balance ,[object Object],[object Object],[object Object]

Two Ways to Balance Redox Equations ,[object Object],[object Object],20.3

Two Ways to Balance Redox Equations ,[object Object],20.3

Two Ways to Balance Redox Equations ,[object Object],20.3 2 ,[object Object]

Lecture 20.3- Balancing Redox

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Lecture 20.3- Balancing Redox