Reaction of Potassium permanganate.
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Speakers: 21709, 10, 21
Teacher:
Background: oxidation-reduction
reaction of Potassium permanganate
1.
When the reaction happens under
different pH value, different ionic
products such as Mn2+, MnO2, MnO42are produced.
1.
Each ion can be produced under acidity,
neutrality, and alkaline
Objectives
Observe the products of the oxidationreduction reaction of Potassium
permanganate which occurs under
different pH environment and establish a
model.
2.Measure the proportion of distinct ions
when reaction happens under different
conditions from acid to alkali condition.
3. Use various organic matters to react with
Potassium permanganate and detect the
product.
1.
Experiment 1: Observation
1.Prepare 0.01M of Potassium
permanganate（dissolved in water）
 2.Prepare 3% hydrogen peroxide
 3.Take 3ml of Potassium permanganate
and add it to 10-ml solutions of different
pH values.
4. Slowly drop hydrogen peroxide into it
and observe the color change.
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Experiment 2: Qualitative analysis
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1.Prepare 0.01M Potassium permanganate aqueous solution.
2. Prepare 3% hydrogen peroxide.
3. Prepare 0.01M 0.1M 1M Sodium hydroxide aqueous solution.
4. Prepare 0.5M 0.05M 0.005M sulfuric acid aqueous solution.
5. Use pH meter to show the pH value of the two solutions.
6. Add 2mL Potassium permanganate aqueous solution into 30mL
Sodium hydroxide aqueous solution.
7. If there are precipitations, put the solution into centrifuge and
take the upper layer solution to run the spectrophotometer.
8. See the highest absorption peak and check if there are
manganese dioxide and MnO42- coexist.
9. Back to step 4 and add 2mL Potassium permanganate aqueous
solution into 30mL sulfuric acid aqueous solution.
10. Put the solution into the spectrophotometer
11. See the highest absorption peak and measure the ratio of
Mn2+.
Experiment 3: Organic matters' reaction
1. Prepare 0.01M Potassium
permanganate
 2. Add 3mL into the organic matter under
acid condition
 3. If the oxidation-reduction reaction
occurs, move the reaction to neutrality
and alkaline condition.
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Results
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In first experiment, we saw the solution turn to be colorless
under pH 5. But under pH 7,we got the brown precipitate
called manganese dioxide. And we got more and more
manganese dioxide when it was under pH 8,9 and 10
In second experiment, we find that if we add Potassium
permanganate aqueous solution into sulfuric acid aqueous
solution (pH 0~2)and drop 3％ hydrogen peroxide into it
slowly, the color of the solution will turn to orange first and
then turn to be colorless ;on the other hand, if we add
Potassium permanganate aqueous solution into Sodium
hydroxide aqueous solution (pH12~14)and drop hydrogen
peroxide into it,the solution’s color will turn to dark green.
Discussions
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1. when we put the same concentration and
amount of Potassium permanganate aqueous
solution and hydrogen peroxide into each buffer,
we find that the solution produces more and
more precipitate(MnO2),so we predict that Mn2+
and MnO2 might coexist.
2. Since we find that the solution which turns to
dark green in the second experiment produces
some precipitation at the bottom , we want to
make our experiment more accurate to make
sure whether MnO42- and MnO4 can coexist. If
that is correct, we can control the pH value, and
then use spectrophotometer to find the ratio
between MnO42- and MnO2 in different pH value.
Future prospect
1. By the spectrophotometer, we expect to
know all the ratio of ion under the
different pH value.
 2. Find out how the pH value affects
MnO4-'s oxidation force.
 3. Figure out the pH border of
Mn2+,MnO2,and MnO42-.
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