March 07, 2013
Predicting Redox Reactions Using the Five Step Method
In a mixture of OA and RA, a reaction will always occur between the SOA and the
SRA.
To predict a redox reaction, follow the following steps:
1) List all the reactants present
-an acidic solution has H+ ions
-a basic solution has OH- ions
-solutions have H2O
2) Label all reactants as oxidizing agents or reducing agents
-remember generalizations
-use the redox table in your data book
-some substances act as both OA and RA
example:
-some OA and RA need to act in combination
example:
3)a) Label the SOA and copy the reduction half reaction from the data book
b) Label the SRA and copy the oxidation half reaction from the data book
4) Equalize electrons by multiplying one or both half reactions by a coefficient, and
add them together.
5) Predict whether the reaction will be spontaneous.
March 07, 2013
Example #1
A solution of copper (II) sulfate is spilled on a steel bench.
(Assume the bench is pure iron)
March 07, 2013
Example #2
Acidified potassium permanganate is slowly poured into a solution of
hydrogen peroxide.
March 07, 2013
Example #3
A strip of gold metal was dipped into a solution of iron (II)
chloride
March 07, 2013
Assignment: Use the five step method to predict the redox reaction that will take
place. Be sure to indicate whether the reaction will be spontaneous or not.
1. An aqueous solution of potassium permanganate was reacted with an acidic
solution of sodium bromide.
2. A strip of silver metal is placed in a solution of nickel (II) chloride.
3. Liquid mercury is mixed with a paste of acidic manganese (IV) oxide.
4. Hydrogen peroxide and silver nitrate solutions are mixed.
5. Potassium metal is placed in some water.
March 07, 2013
6. In a car battery, lead and lead (IV) oxide electrodes are exposed to a sulfuric
acid electrolyte.
7. Concentrated nitrous acid is poured on to a strip of zinc.
8. An unknown strong acid is poured onto a gold ring.
9. Aluminum lawn furniture is exposed to the action of wind (O2) and rain (H2O).
10. Tin (II) bromide solution is added to acidic potassium permanganate solution.
March 07, 2013