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To compare the strength of a specific potassium permanganate solution to a standard ferrous ammonium sulphate (Mohr’s salt) solution in order to assess its potency.
In the presence of sulfuric acid, potassium permanganate is a powerful oxidant, according to theory. Mohr salt is a double salt that forms a single crystalline structure and has the formula (NH4)2. FeSO4. 6H2O. It is also known as Mohr’s salt. Mohr’s salt is referred to by its chemical name as ferrous ammonium sulphate.
It should be noted that in this titration, Mohr salt serves as a reducing agent and potassium permanganate serves as an oxidising agent. The reaction between Mohr’s salt and potassium permanganate is therefore classified as a redox reaction. The process takes place because the ferrous ion from Mohr’s salt is oxidised, and the pink manganese contained in potassium permanganate, which is in the +7 oxidation state, is reduced to the colourless manganese ion (Mn2+).
This titration is based on oxidation-reduction titrations, which are performed in a laboratory. When sulfuric acid is used to titrate ferrous ammonium sulphate solution against potassium permanganate solution in the presence of an acidic media, the results are positive. It is vital to use an acidic media in order to prevent the precipitation of manganese oxide. It is known as permanganate titration in this case because KMnO4 functions as a self indicator in the reaction.
Experiment
Specify the materials you’ll need.
- Mohr’s salt is a type of salt (ferrous ammonium sulfate)
- Permanganate solution (potassium permanganate)
- Sulfuric acid should be diluted.
- Chemical Equilibrium
- Burette
- Stand for the burette
- Pipette
- Flask with a conical shape
- Funnel
- a flask for measuring
- Bottle for weighing
- The colour white is used in the tile.
- Burnet
- Wire gauze is a type of gauze that is made of wire.
Setup of the apparatus:
In the burette, a KMnO4 solution was used.
In a conical flask, combine 10 mL of ferrous ammonium sulphate (Mohr’s salt) with 1 mL of sulfuric acid indicator (Sulfuric acid indicator – Self indicator) (KMnO4)
Point of no return – Colourless to a permanent pale pink colour
Titration of Mohr salts using KMnO4
Procedure: (a) Prepare a 0.05M standard solution of ferrous ammonium sulphate by following the following steps:
To determine the amount of Mohr’s salt necessary for 250ml of a solution with a normality of 0.05N, use the following formula:
Molar mass of mohr’s salt is 392 g/mol (grams per mole).
Strength = Normality x Equivalent weight = (1/20) x 392 = 19.6 g/L Strength = Normality x Equivalent weight
When preparing 250mL of N/20 Mohr’s salt solution, the amount of Mohr salt required is (19.6/1000) x 250 = 4.9 grams (molecular weight).
Using a chemical balance, weigh an empty watch glass to see how much it weighs.
Measure and record the weight of 4.9g of Mohr’s salt on a chemical balance.
Use a funnel to put the Mohr’s salt into the measuring flask, then discard the funnel.
Remove the funnel from the flask and wash it with distilled water while keeping the funnel in place.
Using pure water, bring the solution up to the specified point and check to see that the Mohr’s salt has been completely dissolved.
A 0.05N standard solution of Mohr’s salt is used in this solution.
In order to compare potassium permanganate solution to conventional ferrous ammonium sulphate (Mohr’s salt) solution, the following procedure was used:
Wash and rinse the burette and pipette with distilled water before rinsing them with the solution that will be placed within them.
Using the potassium permanganate solution, rinse the burette and then fill the burette with the potassium permanganate solution.
The burette should be secured in the burette stand, and the white tile should be placed beneath the burette in order to appropriately locate the terminus.
Remove the pipette and conical flask from the solution and rinse them with normal ferrous sulphate solution.
Pipette 10ml of 0.05N standard Mohr’s salt solution into the conical flask using a sterile tip.
Sulfuric acid should be added to the test tube to avoid the oxidation of manganese and the formation of manganese dioxide.
Make a mental note of the initial reading in the burette before beginning the titration process.
The titration procedure is now initiated; titrate the solution against potassium permanganate solution while gently swirling the solution in the flask.
Initially, ferrous ammonium sulphate is used to remove the purple colour of KMnO4 from the solution. The emergence of a permanent pink colour indicates the completion of the process.
Continue the titration process until concordant values are achieved.
The upper meniscus should be noted down on the burette readings.
Take note of the reading and enter it into the observation table provided below in order to calculate how much KMnO4 is present in the solution.
Conclusion:
Therefore we can finally conclude that the molarity of the provided KMnO4 solution is moles per litre of solution. The concentration of potassium permanganate solution in the sample is g/L. Because potassium permanganate is a black compound, it is important to carefully read the top meniscus. Before using the pipette and burette, thoroughly rinse them. Acidification of potassium permanganate should be accomplished with weak sulfuric acid. Before beginning the experiment, thoroughly clean all of the apparatus with distilled water and then thoroughly rinse with the solution that will be used in them. Once it reaches the endpoint, it should take correct readings rather than settling for average results. It is not recommended to use a rubber cork burette since it can be affected by KMnO4. While taking the burette readings, make use of the antiparallel card or the auto parallax card. There should be no more than two decimal places used when calculating the strength of an unknown solution.
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