You will miss the endpoint

You will not be able to correctly establish the actual volume required for the colour change from purple to colourles - ie. the end points. This is critical as it is used in your calculations. I know it is tedious, but you can lways try to use an auto titrator instead of doing the titration manually, which will give you an accurate result without any hassles.

Dear Saif

Reaction rates for the oxidation of constituents found in natural waters are relatively fast and depend on temperature, pH, and dosage. must use an auto titrator to make a control for your titration

If the endpoint of my reaction would be around 20ml of the titrant (KMnO4).so I flushed 17 ml of the titrant for the third trial all at once in the analyte. why would this affect my results although I haven't reach my endpoint yet?

By colour indication method you have to take care so that end point will not be missed. Moreover in this case KMnO4 itself acts as indicator. Hence in case the reaction neutralisation point is crossed you will not be in a position to catch exact volume of reactant. It is better to follow potentiometric titration in order to avoid difficulty in judgement of end point by colour change.

It is better add slowly for avoid the formation of MnO2 that reactive less fast at Mn2+

The titration should be made in a solution very hot, in this way the reaction is faster.

My teacher said that you must give the time for form some Mn2+, that after have catalytic effect, So he said first add slowly the KMnO4 and after you can increment the speed of the titration, always in hot solution.

Thank you all for your answers. It is deeply appreciated Thank you all again

What can be the strongest reducing agent for KMnO4.

A reducing agent of which 1-3 gram (any sulphate salt)is enough to turn 1 litre of KMnO4 (2 g/L concentration) into colourless solution.

Mete bisulfite even require more amount to reduce 10-12 g.

Redox reactions, or oxidation-reduction reactions, are reactions in which electrons are transferred between substances. These reactions are fundamental in the field of electrochemistry and are widely used in various analytical methods, including titration.

Potassium permanganate (KMnO4) is a common reagent used in redox titrations due to its strong oxidizing properties and the distinct color change it undergoes during a reaction. It can determine the amount of reducing agents in a solution. When KMnO4 is added to a solution containing a reducing agent, it will accept electrons from the reducing agent and be reduced itself. The endpoint of the titration is usually indicated by a persistent pink color due to the presence of a slight excess of MnO4^- ions, which indicates that all the reducing agent has been oxidized.

In a more rigorous sense, the stoichiometry of the reaction must be known, and the titration should be carried out under acidic conditions because KMnO4 is most stable in acid. The titration's accuracy depends on the precise measurement of the volume of KMnO4 solution needed to reach the endpoint and the concentration of KMnO4. It's also important to note that the reaction can be influenced by temperature and the presence of other ions that might interfere with the reaction.

Proper technique is crucial, including slow addition of the titrant with constant stirring to ensure complete reaction and accurate endpoint determination. Calibration of the KMnO4 solution against a standard, like sodium oxalate, is often necessary to ensure the accuracy of the titration results.

l This protocol list might provide further insights to address this issue.

Acidified KMnO4 is a strong oxidizing agent and when it is titrated with a reducing agent, such titration is called REDOX titration. The end point of the redox titration can be detected by using an indicator or by adopting potentiometric titration. If you add more volume of titrant at a time you may not be able to notice the exact end point. If excess titrant is added at a time the neutralisation point will be crossed. Hence you have to add small aliquot of titrants with continuous mixing of both reactants in the titration vessel during titration in order to get the exact end point. If you want very precise measurement it is better to adopt potentiometric titration. Now a days the entire kinetic of reaction during titration can be monitored online by using automated titrators from the online titration plot and more precisely by using derivative plot. In my laboratory we have developed a new type of potentiometric titrator viz. pulsating potentiometric titration device and we have deployed such device to conduct trace level analysis even at sub ppm level for example assay of dissolved oxygen in water at sub ppm level in much easier way.

Redox titration using KMnO4, or potassium permanganate, is a common analytical method for determining the concentration of oxidizable substances. Here's how it is generally performed:

1. Preparation: Prepare a standard solution of KMnO4, typically of a known molarity. The solution should be standardized against a primary standard.

2. Sample Preparation: If the substance to be titrated is solid, dissolve it in a suitable solvent to make a known concentration of the solution. If it's already in a solution, you may use it directly.

3. Acidic Medium: Ensure that the titration is performed in an acidic medium because KMnO4 is most stable in acid. Usually, sulfuric acid is added to the solution to provide the acidic environment.

4. Titration Setup: Set up the burette with KMnO4 and place the solution to be titrated in a conical flask. Add a stirring bar if using a magnetic stirrer.

5. Endpoint Detection: In a redox titration with KMnO4, the endpoint is indicated by a persistent pink color. KMnO4 acts as its own indicator, turning from colorless in a reduced state to pink/magenta in the oxidized state.

6. Titration Process: Add KMnO4 dropwise to the solution, stirring constantly until the endpoint is reached, indicated by a light persistent pink color that lasts for about 30 seconds.

7. Calculations: The molarity of the KMnO4 solution and the volume used in titration allow for the calculation of the number of moles of KMnO4 used, which can then be related to the number of moles of the substance being titrated using the stoichiometry of the reaction.

8. Repeat for Accuracy: To ensure accuracy, the titration should be repeated until consistent results are obtained.

This procedure is useful for analyzing substances such as ferrous salts, oxalates, and certain organic compounds. It is valued for its precision and the visual simplicity of endpoint detection.

Perhaps this protocol list can give us more information to help solve the problem.