Introduction:1. concept of redox system: Redox system can be defined as a chemical reaction in which atoms’ oxidation states can be changed. Redox system has a formal name which is called ”oxidation-reduction reaction”. These two processes occur together.
Normally, there isn’t an oxidation reaction without a reduction reaction. This system looks like transplantation of organs. For example, you can’t have a recipient if you don’t have a donor and vice versa. The oxidation process is referred to gaining of bonds to oxygen or it is a process of loss of electrons and increase in oxidation number.
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Some examples of compounds which can be oxidized are some organic fuel substances like, gas, wood or coal. These substances carbon atoms will form bonds with oxygen in burning process, and some of oxygen can be used to burn the fuel bonds to the hydrogen atoms from the fuel. The reduction process can be defined as gaining of hydrogen or in another way, it is the gain of electrons which lead to decrease in oxidation number. C7H12+11O2 — 7CO2+8H2OIn this equation, heptane’s carbon atoms are oxidized, but oxygen atoms are reduced. Rusting process is an example of redox system. This process is explained by iron equation,Fe+H2O+O2 — Fe2O3.If the oxidation reaction occurs, iron will lose electrons in the presence of H2O and acquire a positive charge.Fe — Fe2+ +2e- If the reduction reaction occurs, oxygen will be reduced.
O2+4e- +4H+ — 2H2O. And then, iron ions will react with hydroxide ions and lead to the formation of iron hydroxide that will dry in many steps to give a rust.Fe2+ +2OH- — Fe(OH)2 —- Fe2O3 (rust).Rust reaction can occur in dry conditions but it will be slow, so it is better to be done in the presence of moisture because redox reactions need water.
An indicator which is used in the preparation of KMNo4: Potassium permenganate can be used as a self indicator.There is another self indicator which is called iodine (I2). Titrant which is used in this preparation:There is no titrant, because this assignment is about the preparation of potassium permrngante not about titration. Uses of potassium permenganate:KMNO4 has several uses even if they are medical uses or other uses.
Some medical uses of potassium permenganate are:1. Treatment of skin infections such as canker sores, eczema, acne and dermatitis, we need a small dilute amount of it in the treatment of small wounds.2. Treatment of fungal infections like athlete’s foot. This condition has some symptoms such as burning or itching, it occurs especially between toes. KMNO4 can treat this condition by putting the affected foot in its solution, and dissolved in water for 15min twice a day for two or three weeks.
3. Allergies of hair dye: KMNO4 contain a non-oxidized dye which is mixed with developer to break down the melanin, and then, this dye replace the melanin. Other uses of KMNO4:- Purifying water.- Emergency signal in marking snow.- As a disinfectant agent.
– Preparation of antiseptic solution.Properties of potassium permenganate:KMNO4 has some properties. These properties include, – It can’t be considered as a primary standard.- It is a self indicator.- It is a very strong oxidizing agent.- It is an impure solution.- It is unstable.
– Solution of it can rapidly deteriorate on standing.- KMNO4 can dissolve in an alkaline and acidic medium, in each medium it gives different products. For example, in acidic medium it is converted into manganeseMno4-+8H+ +5e — Mn2+ +4H2O.In slightly alkaline medium, it gives a brown product of Mno2.Mno4- +4H+ +3e — Mno2+2H2O.,and in strong alkaline medium, it gives a green Mno42- product.Mno4+e — Mno42- Experiment Layout,- Apparatus needed for this preparation:1.
Burette.2. Burette stand.
3. Volumetric flask.4. Distelled water.
5. Watch glass.6.
Funnel.Procedure:1. Take 100ml of stock KMNO4 from the burette into 500ml volumetric flask.2. Complete to the mark in the flask with distilled water.
3. Then, shake well.There is another way to prepare KMNO4, this way is done in some steps,1. Dissolve KMNO4 reagent grade in 1L of water, which should be purified.2.
Heat on a steam bath for two hours.3. Cover and then, let it stand for 24hr.4. Filter through sintered glass.5.
Store in a closed container and put it away from the light.Standardization of potassium permenganate:This step can be done by using sodium oxalate:- Mno4- + 8H+ +Fe — Mn2+ + 4H2O.- C2O42- — 2CO2+2e.By adding the two equations to each other, the final equation will be:- 2Mno4- +16H+ +5C2O42- +10e — 10CO2+2Mn2+ +8H2O +10e. Procedure of standardization of KMNO4:1. Fill the burette with 0.4N KMNO4.
2. Take 10ml Sodium Oxalate in a conical flask.3. Add 20ml of H2SO4.4.
Heat to 60c.5. Titrate to the first presistent pink end point.
Results:The Volume needed from conc KMNO4 solution can be calculated from the equation, this equation said that:N V = N’ V’., in which – N means normality of conc solution.- V means volume of conc solution.- N’ means volume, which required for dilluted solution preparation.- V’ means normality of diluted solution. In case of preparing 500ml 0.4N KMNO4,N V = N’ V’2x? = 0.
4×500 = 100ml.Standardization factor can be measured from,Mls of Na oxalate/ mls of KMNO4 (E.P). Precautions:1. Someone should be careful when he uses KMNO4 because it can leave a purple stain on his clothes or it may cause irritation to the skin.2. KMNO4 solution must let to be dried for two hours at least at 105-110c, and then cooled in the device which is called a dessicator.3.
Heating a permenganate solution in the glassware to precondition them, and then using deionized water to risie them well.4. Avoid over-heating of permenganate because this will lead to decomposition of the sample.5. Store KMNO4 solution away from light in a vessel which have a glass stopper, and never be plastic.6. Tie hair or scarf back.7.
Don’t wear open shoes, but covered shoes.8. If a chemical move on someone’s skin, he should use the water on an affected area for 15min. Conclusion: From the above, it seems that potassium permenganate preparation is a type of redox system or ”oxidation-reduction process”. This product has some properties and uses. It is considered as a self indicator so, in its preparation, it doesn’t need an indicator and it can be considered as a very strong oxidizing agent. Potassium permenganate uses include, treatment of fungal or skin infections and other uses. This product can be prepared by two methods which are discussed before.
Finally, when someone needs to prepare potassium permenganate, he must be careful due to its several precautions.