8 Questions
What is the purpose of titrating the permanganate and oxalate solutions in hot conditions?
To make the reaction practical due to oxalate's slow reactivity at room temperature
What color change indicates the endpoint of the titration?
Colorless to pink
Why does the solution turn from dark purple to a faint pink color at the equivalence point during the redox titration?
Due to the reduction of permanganate ion to Mn+2 ion
Why is potassium permanganate solution standardized against potassium oxalate?
To determine the exact normality of permanganate solution
What role does Oxalic acid play in the redox titration involving potassium permanganate?
Being reduced by permanganate ions
How does potassium permanganate act as an auto catalyst in the reaction with Oxalic acid?
By reducing itself to form manganese intermediate states
Why can potassium permanganate serve as its own indicator in the redox titration process?
The pink color change is distinguishable
Which ion acts as a catalyst in the reaction between Oxalic acid and permanganate during titration?
+2 ion (Mn+2)
Study Notes
Redox Titration Experiment
- Objectives of the experiment:
- Practice the normality term in preparing a solution of an oxidizing agent
- Standardize the oxidizing agent solution by titrating it with a standard solution of a reducing agent
Introduction to Redox Titration
- Redox titration is a type of titration based on the loss or gain of electrons between the analyte and the titrant
- Potassium permanganate (KMnO4) is a strong oxidizing agent
- Permanganate ion (MnO4-) is intense dark purple in color
- Reduction of purple permanganate ion to the colorless Mn+2 ion changes the solution from dark purple to faint pink at the equivalence point
Reaction Mechanism
- The direct reaction is slow, but Mn+2 ions produced in the reaction act as a catalyst, reacting with permanganate to form intermediate oxidation states of manganese
- These states react rapidly with Oxalic acid to give the products, making KMnO4 an auto-catalyst in this reaction
Experimental Procedure
- Weigh and transfer Oxalic acid sample to a 250 mL Erlenmeyer flask
- Rinse and fill the burette with the KMnO4 solution
- Add 50 mL of distilled water and 5 mL of 6 N H2SO4 to the oxalate sample in the Erlenmeyer flask
- Heat the acidified oxalate solution to about 85°C, then titrate with the KMnO4 solution until a faint pink color appears
Calculations and Questions
- Calculate the normality of KMnO4 stock solution
- Calculate the normality of standard KMnO4 solution after titration
- Write a balanced redox equation for the reaction of permanganate with oxalate in an acidic solution
- How many electrons lost or gained by each half reaction?
Reaction Equation
- MnO4- + C2O42- → Mn2+ + CO2 (acidic solution)
Standardization of KMnO4 Solution
- Weigh approximately 0.1 g KMnO4 crystals and transfer to a 500mL Erlenmeyer flask
- Add 350 mL of distilled water to dissolve the KMnO4 crystals
- Heat the solution with occasional swirling, then allow it to cool
Test your knowledge of a chemistry lab procedure involving transferring a sample, rinsing a burette, adding substances to a flask, heating the solution, and titrating with KMnO4 solution. Practice recording measurements accurately in a lab setting.
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