16 Questions
What is the purpose of titrating the permanganate solution hot in this experiment?
To make the procedure practical due to oxalate reacting very slowly at room temperature.
Using the half-reaction method, write a balanced redox equation for the reaction of permanganate with oxalate in an acidic solution.
2MnO4- + 5C2O42- + 16H+ -> 2Mn2+ + 10CO2 + 8H2O
How many electrons are lost or gained by each half reaction in the given reaction?
Permanganate: 5 electrons lost; Oxalate: 2 electrons gained
Why is HNO3 or HCl not used in redox titration?
HNO3 or HCl would react with permanganate and interfere with the titration process.
What is the objective of standardizing the oxidizing agent solution in redox titration?
To titrate it with a standard solution of a reducing agent
Why does the solution turn from dark purple to faint pink at the equivalence point in the redox titration with potassium permanganate?
Reduction of purple permanganate ion to the colorless Mn+2 ion
What role does potassium permanganate (KMnO4) play in redox titration?
It serves as its own indicator
Why is the first direct reaction slow in a redox titration involving permanganate and Oxalic acid?
Mn+2 ions produced in the reaction act as a catalyst
What is the advantage of using KMnO4 in redox titrations?
It acts as an auto catalyst in the reaction
How can the normality term be practiced in preparing a solution of an oxidizing agent?
By preparing a solution with a known concentration and volume
What is the purpose of adding 6 N H2SO4 to the oxalate sample in the Erlenmeyer flask?
To acidify the solution and provide H+ ions for the redox reaction.
Why is it important to heat the acidified oxalate solution to about 85°C?
To increase the reaction rate between KMnO4 and oxalate, facilitating the titration process.
What is the significance of recording the initial and final burette readings during titration?
To determine the volume of KMnO4 solution used, which is crucial for calculating the concentration of the solution.
Explain the role of oxalic acid solution in washing the burette and titration flask.
To remove any residual KMnO4 solution and prevent contamination in subsequent titrations.
What does the equation n2 M1V1 = n1M2 V2 represent in the context of this redox titration?
It represents the stoichiometry of the reaction between KMnO4 and oxalate based on their molar ratios.
How does the redox reaction between permanganate and oxalate involve both oxidation and reduction processes?
MnO4- is reduced to Mn2+ (from +7 to +2) while oxalate is oxidized to CO2.
Study Notes
Importance of Titrating Permanganate Solution
- Titrating the permanganate solution hot is necessary to increase the reaction rate between permanganate and oxalate.
Balanced Redox Equation
- The balanced redox equation for the reaction of permanganate with oxalate in an acidic solution can be written using the half-reaction method.
Electron Transfer in Half-Reactions
- In the given reaction, 5 electrons are gained by permanganate (MnO4-) and 2 electrons are lost by oxalate (C2O42-).
Choice of Acid in Redox Titration
- HNO3 or HCl cannot be used in redox titration because they would oxidize oxalate, interfering with the reaction.
Standardizing the Oxidizing Agent
- The objective of standardizing the oxidizing agent solution (KMnO4) in redox titration is to determine its exact concentration.
Color Change at Equivalence Point
- At the equivalence point, the solution turns from dark purple to faint pink due to the complete reaction of permanganate with oxalate.
Role of Potassium Permanganate
- Potassium permanganate (KMnO4) acts as a strong oxidizing agent in redox titration, oxidizing oxalate to carbon dioxide.
Rate of Initial Reaction
- The first direct reaction between permanganate and oxalic acid is slow due to the low reactivity of oxalic acid.
Advantages of KMnO4
- The advantage of using KMnO4 in redox titrations is its strong oxidizing power, allowing it to react completely with oxalate.
Preparing a Solution of an Oxidizing Agent
- The normality term can be practiced in preparing a solution of an oxidizing agent by adjusting the concentration to a known value.
Adding H2SO4 to Oxalate Sample
- 6 N H2SO4 is added to the oxalate sample to create an acidic environment, necessary for the reaction to occur.
Heating the Acidified Oxalate Solution
- Heating the acidified oxalate solution to about 85°C increases the reaction rate and ensures complete reaction with permanganate.
Importance of Burette Readings
- Recording the initial and final burette readings during titration is essential to calculate the volume of permanganate solution consumed.
Washing the Burette and Titration Flask
- Oxalic acid solution is used to wash the burette and titration flask to remove any residual permanganate ions.
Mole Ratio in Titration
- The equation n2 M1V1 = n1M2 V2 represents the mole ratio of the reactants in the titration, where n is the number of moles, M is the molarity, and V is the volume.
Redox Reaction Mechanism
- The redox reaction between permanganate and oxalate involves both oxidation (oxalate loses electrons) and reduction (permanganate gains electrons) processes.
This quiz covers Experiment 7 on Redox Titration in Analytical Chemistry, where students practice the normality term in preparing a solution of an oxidizing agent and standardize the oxidizing agent solution by titrating it with a standard solution of a reducing agent.
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