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Questions and Answers
What is the purpose of adding dilute sulfuric acid to the iron(II) solution in the conical flask?
What is the purpose of adding dilute sulfuric acid to the iron(II) solution in the conical flask?
During the titration, what indicates that the end-point has been reached?
During the titration, what indicates that the end-point has been reached?
What should be done to the burette before starting the titration?
What should be done to the burette before starting the titration?
How is the concentration of the iron(II) solution calculated at the end of the titration process?
How is the concentration of the iron(II) solution calculated at the end of the titration process?
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What is the mole ratio between potassium manganate(VII) and iron(II) ions in the reaction?
What is the mole ratio between potassium manganate(VII) and iron(II) ions in the reaction?
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What is the total mass of five iron tablets mentioned in the procedure?
What is the total mass of five iron tablets mentioned in the procedure?
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Before beginning the titration, which step is crucial regarding the solutions in the pipette and burette?
Before beginning the titration, which step is crucial regarding the solutions in the pipette and burette?
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What role does the white tile play during the titration?
What role does the white tile play during the titration?
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What is the mass of iron in each tablet containing FeSO₄?
What is the mass of iron in each tablet containing FeSO₄?
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What is the percentage of FeSO₄ in each tablet?
What is the percentage of FeSO₄ in each tablet?
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What is the first step in preparing the sodium thiosulfate solution for the titration?
What is the first step in preparing the sodium thiosulfate solution for the titration?
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How many grams of FeSO₄ are in a 250 cm³ volumetric flask with a concentration of 2.63 g/L?
How many grams of FeSO₄ are in a 250 cm³ volumetric flask with a concentration of 2.63 g/L?
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What is the molarity of the sodium thiosulfate solution given that 25 cm³ of a 0.045 M iodine solution is titrated to an average of 27.45 cm³?
What is the molarity of the sodium thiosulfate solution given that 25 cm³ of a 0.045 M iodine solution is titrated to an average of 27.45 cm³?
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What color change indicates the end-point of the titration with sodium thiosulfate?
What color change indicates the end-point of the titration with sodium thiosulfate?
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What is the total mass of iron in 5 tablets of FeSO₄?
What is the total mass of iron in 5 tablets of FeSO₄?
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What procedure is indicated for dosing sodium thiosulfate during the titration?
What procedure is indicated for dosing sodium thiosulfate during the titration?
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What is the molarity (M) of sodium thiosulfate after the titration calculation?
What is the molarity (M) of sodium thiosulfate after the titration calculation?
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How much sodium thiosulfate is required to reach the end-point of the titration?
How much sodium thiosulfate is required to reach the end-point of the titration?
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What should be done after adding potassium iodide and dilute sulfuric acid to the conical flask?
What should be done after adding potassium iodide and dilute sulfuric acid to the conical flask?
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What color change indicates the end-point of the titration?
What color change indicates the end-point of the titration?
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What is the purpose of washing the pipette, burette, and conical flask with deionised water before use?
What is the purpose of washing the pipette, burette, and conical flask with deionised water before use?
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What was the reason for using excess potassium iodide during the procedure?
What was the reason for using excess potassium iodide during the procedure?
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The reaction equation shows that how many moles of thiosulfate are consumed for each mole of iodine?
The reaction equation shows that how many moles of thiosulfate are consumed for each mole of iodine?
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In the titration process, why is the conical flask placed on a white tile?
In the titration process, why is the conical flask placed on a white tile?
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What is the first step in preparing the bleach solution for titration?
What is the first step in preparing the bleach solution for titration?
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What indicator is used in the titration to observe the color change?
What indicator is used in the titration to observe the color change?
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What is the final volume of sodium thiosulfate used in the average titration?
What is the final volume of sodium thiosulfate used in the average titration?
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What indicator is used in the titrations and what color change occurs at the endpoint?
What indicator is used in the titrations and what color change occurs at the endpoint?
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What is the concentration of NaClO in the original bleach solution expressed in moles per liter?
What is the concentration of NaClO in the original bleach solution expressed in moles per liter?
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What is the primary role of potassium permanganate in volumetric analysis?
What is the primary role of potassium permanganate in volumetric analysis?
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Why must potassium permanganate be standardised before use?
Why must potassium permanganate be standardised before use?
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What ions are formed when Fe^2+ ions are oxidised by potassium permanganate?
What ions are formed when Fe^2+ ions are oxidised by potassium permanganate?
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How many Fe^2+ ions are needed to react with one MnO^4- ion?
How many Fe^2+ ions are needed to react with one MnO^4- ion?
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What is the necessary action to prepare the iron(II) solution for titration?
What is the necessary action to prepare the iron(II) solution for titration?
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What property of ammonium iron (II) sulfate makes it suitable as a primary standard?
What property of ammonium iron (II) sulfate makes it suitable as a primary standard?
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Which step is essential to take before filling the burette with potassium manganate(VII) solution?
Which step is essential to take before filling the burette with potassium manganate(VII) solution?
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From which part of the meniscus should readings be taken when measuring potassium manganate(VII) solution?
From which part of the meniscus should readings be taken when measuring potassium manganate(VII) solution?
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What is the concentration of sodium hypochlorite in the diluted bleach solution in moles per litre?
What is the concentration of sodium hypochlorite in the diluted bleach solution in moles per litre?
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How many grams of sodium hypochlorite are present in one litre of the diluted bleach solution?
How many grams of sodium hypochlorite are present in one litre of the diluted bleach solution?
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What is the percent weight/volume concentration (w/v) of sodium hypochlorite in the diluted bleach?
What is the percent weight/volume concentration (w/v) of sodium hypochlorite in the diluted bleach?
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If the original bleach solution was diluted 10 times, what is the concentration of sodium hypochlorite in the original bleaching solution in moles per litre?
If the original bleach solution was diluted 10 times, what is the concentration of sodium hypochlorite in the original bleaching solution in moles per litre?
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What is the molecular mass of sodium hypochlorite (NaClO)?
What is the molecular mass of sodium hypochlorite (NaClO)?
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During the titration, which compound was used as the titrant with a concentration of 0.12 M?
During the titration, which compound was used as the titrant with a concentration of 0.12 M?
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What is the amount of grams of sodium hypochlorite present per 100 cm^3 in the original bleach?
What is the amount of grams of sodium hypochlorite present per 100 cm^3 in the original bleach?
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Which ion reacts with sodium hypochlorite in the titration process?
Which ion reacts with sodium hypochlorite in the titration process?
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Study Notes
Volumetric Analysis: Oxidation-Reduction
- Volumetric analysis is used to determine the concentrations of oxidizing and reducing agents. Potassium permanganate (KMnO4) is a crucial oxidizing agent.
- Potassium permanganate is a purple solid, not a primary standard (cannot be obtained in high purity).
- It needs standardization by titration against a primary standard solution.
- In acidic solution, KMnO4 gains five electrons and acts as an oxidizing agent: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O (purple → colorless).
- To react, dilute acid must be added to provide H+ ions.
- KMnO4 is its own indicator.
The Reaction of MnO4- and Fe2+
- The concentration of KMnO4 solution can be determined by titrating it against a solution containing Fe2+ ions.
- KMnO4 acts as an oxidizing agent, converting Fe2+ to Fe3+.
- The reaction equation is: MnO4- + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O.
- Five Fe2+ ions react with one MnO4- ion.
- Ammonium iron(II) sulfate (source of Fe2+) is a primary standard, pure, and not affected by air.
Mandatory Experiment: Standardization of KMnO4
- Steps to prepare a standard solution of ammonium iron(II) sulfate and standardize a KMnO4 solution by titration:
- Wash glassware with deionized water. Rinse the burette and pipette with their respective solutions.
- Use a pipette to measure the iron(II) solution and transfer it to a conical flask. Add dilute sulfuric acid to acidify the solution.
- Fill the burette with KMnO4 solution, ensuring the part below the tap is filled to adjust to zero.
- Titrate the KMnO4 solution against the iron(II) solution, swirling the flask continuously and washing down the sides with deionized water.
- Watch for the first persistent pale pink color (endpoint), note the burette reading.
- Repeat the titration procedure until two titres agree within 0.1 cm3.
Solving Volumetric Problems in Redox Reactions
- Equations for calculating concentration:
- Mox Vox nox = Mred Vred nred
- Mo = (nr * Mre *Vre) / (no * Vo)
Mandatory Experiment: Determining Iron Content in Tablets
- Steps to determine the amount of iron in an iron tablet:
- Weigh five iron tablets.
- Crush the tablets and dissolve the ground material in dilute sulfuric acid.
- Transfer to a 250 cm3 volumetric flask, make up to the mark with deionized water and invert.
- Wash glassware with deionized water and rinse the burette and pipette with the appropriate solutions.
- Use a pipette to measure the iron(II) solution and transfer it to a conical flask. Acidify.
- Fill the burette with KMnO4 solution.
- Add the KMnO4 solution to the iron(II) solution in the conical (endpoint is pink colour).
- Record the final burette reading. Repeat twice.
- Calculate the concentration of the iron(II) solution.
- Calculate the mass of iron in each tablet.
Mandatory Experiment: Sodium Thiosulfate Standardization
- Steps to prepare a solution of sodium thiosulfate and standardize it by titration against a solution of iodine:
- Wash glassware. Rinse burette and pipette with the appropriate solutions.
- Fill a pipette with potassium iodate (KI) solution and transfer it to a conical flask. Add sulfuric acid and potassium iodide solution.
- Fill a burette with sodium thiosulfate (Na2S2O3) solution.
- Add Na2S2O3 solution to KI solution, swirling constantly and washing down the sides, until the colour changes (from blue/black to colourless).
- Record the burette reading. Repeat until two titres are within 0.1cm³.
- Calculate the concentration of Na2S2O3 solution.
Mandatory Experiment: Determining Percentage of Sodium Hypochlorite in Household Bleach
- Steps to determine the percentage (w/v) of sodium hypochlorite in household bleach:
- Dilute the bleach to a suitable concentration for titration.
- Wash glassware. Rinse burette and pipette with the appropriate solutions.
- Using a pipette, measure a portion of diluted bleach solution and place in a conical flask. Add potassium iodide and sulphuric acid.
- Fill a burette with Na2S2O3 solution
- Add Na2S2O3 solution to the bleach solution, swirling constantly, and wash down sides. Add starch indicator before end point.
- Record the burette reading. Repeat until two titres agree to within 0.1cm³.
- Calculate the concentration of sodium hypochlorite in household bleach.
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Description
This quiz focuses on volumetric analysis in oxidation-reduction reactions, specifically involving potassium permanganate (KMnO4) and its reactions with Fe2+. It explores the standardization of KMnO4 and its role as an oxidizing agent in acidic solutions. Test your understanding of these concepts and reactions!
