permanganate versus oxalate presentation
TRANSCRIPT
PERMANGANATE VERSUSOXALATE
Reporters: Ken Alexander P. BautroLarry Andrew L. GaleonNece Jean P. TagamMary Jann Kestle Z. Tamayo
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OBJECTIVES:
To prepare 0.72N Sulfuric acid (H2SO4);
To standardize a Permanganate solution against Primary Standard Sodium Oxalate (Na2C2O4);
To calculate % Na2C2O4 in unknown sample.
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MATERIALS/CHEMICALS:Materials: Bunsen burner, clay
pot, wire gauze, asbestos mat, brown bottle, balance, graduated cylinder, beaker, thermometer, stirring rod, buret, buret clamp, iron stand.
Chemicals: H2C2O4, MnO4-
solution, H2SO4, Na2C2O4
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SCHEMATIC DIAGRAM:
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CALCULATIONS:For preparation of .72N H2SO4
.72N H2SO x =0.36M H2SO4
9N H2SO4 x = 4.5 M H2SO4
M1V1=M2V2
(4.5 M H2SO4) (V1) = (0.36M H2SO4) (0.250L H2SO4)
V1 = .02L or 20mL H2SO4
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CALCULATIONS:
For preparation 250mL Permanganate solution
= 0.8 g KMnO4
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Concentration of KMnO4 can be computed by:
CKMnO4 = (g Na2C2O4)(MNa2C2O4)(Molar ratio)
L KMnO4
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BACKGROUND: The permanganate ion, MnO4
-, is a powerful oxidizing agent. It reacts to form Mn2+ ion
MnO4- + 8H+ +5e- ----> Mn2+ + 4 H2O
So the Manganese goes from an oxidation state of +7 to +2
Each MnO4- ion will therefore consume 5 electrons It will oxidize another species, stealing the 5 electrons in the process
Since H+ is also consumed, the reaction will need to be done in an acidic solution.
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BACKGROUND: The Oxalate ion is stable, but can be oxidized
C2O42- --------> 2 CO2 + 2e-
• The C in oxalate is in an oxidation state of +5• The C in CO2 has an oxidation state of +4
• So each carbon will release 1 electron • Each oxalate will release 2 electrons • Equation for the oxidation of oxalate by permanganate in acidic solution:2 MnO4
-(aq ) + 5 H2C2O4(aq ) + 6 H3O+(aq ) --> 2Mn2+(aq ) + 10 CO2(aq ) + 14 H2O
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AUTOCATALYSIS: REACTION OF PERMANGANATE WITH OXALIC ACID
A dilute purple solution of potassium permanganate is added to each of two beakers of acidified oxalate solution. A few crystals of manganese(II) sulfate added to the solution on the right catalyze the reduction of permanganate to colorless manganese(II) ion. Note the initial red color due to formation of a manganese(III) intermediate in the beaker on the right.
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POTASSIUM PERMANGANATE IS ADDED.
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MANGANESE(II) SULFATE IS ADDED TO THE SOLUTION ON THE RIGHT.
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IT CATALYZES THE REDUCTION OF PERMANGANATE TO COLORLESS MANGANESE(II) ION.
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THE OTHER SOLUTION'S REACTION RATE EVENTUALLY INCREASES AS IT FORMS MANGANESE(II) ION, WHICH SUBSEQUENTLY AUTOCATALYZES ITS OWN FORMATION.
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FINDING THE ENDPOINT:
In addition to being a strong oxidizing agent, Permanganate has another important property. It is a compound with an intense purple color. Even one drop of our titrant, KMnO4, is enough to produce a strong pink color. In this case we simply titrate until the solution remains pink.
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ENDPOINT:Pre
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RUNNING A BLANK:
Perform a blank titration every time (it provides a more neutral starting point for the real titration) and the chance of batch failure will be greatly reduced
>>THE END<<
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