Permanganometry is one of the techniques used in qualitative analysis in Chemistry. It is a redox titration

Redox titration

Redox titration is a type of titration based on a redox reaction between the analyte and titrant.Redox titration may involve the use of a redox indicator and/or a potentiometer.-Example:...

 and involves the use of permanganate

Permanganate

A permanganate is the general name for a chemical compound containing the manganate ion, . Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizing agent. The ion has tetrahedral geometry...

s and is used to estimate the amount of analyte

Analyte

An analyte, or component , is a substance or chemical constituent that is of interest in an analytical procedure. Grammatically, it is important to note that experiments always seek to measure properties of analytes—and that analytes themselves can never be measured. For instance, one cannot...

 present in unknown chemical samples.
It involves two steps, namely the titration

Titration

Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the...

 of the analyte with potassium permanganate

Potassium permanganate

Potassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...

 solution and then the standardization of potassium permanganate solution with standard sodium oxalate solution. The titration involves volumetric manipulations to prepare the analyte solutions.

Depending on how the titration

Titration

Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the...

 is performed, the permanganate

Permanganate

A permanganate is the general name for a chemical compound containing the manganate ion, . Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizing agent. The ion has tetrahedral geometry...

 ion can be reduced to Mn^x, where x is +2, +3, +4 and +6. Using permanganometry we can estimate the quantitative presence of Fe⁺², Mn⁺², Fe⁺² and Mn⁺² when they are both present in a mixture, C₂O₄^2-, NO₂^-, H₂O₂ etc.

In the most cases permanganometry is performed in a very acidic solution in which the following reaction occurs:

MnO₄^- + 8H⁺ + 5e^- = Mn⁺² + 4H₂O

The standard potential of this electrochemical reaction is:

E^o=+1.52 V

which shows that KMnO₄ (in an acidic medium) is a very strong oxidizing agent. With this method we can
oxidize:

• Fe
  Iron
  Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
  
  ⁺² (E^o_{Fe⁺³/Fe⁺²}=+0.77 V)
• Sn
  Tin
  Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
  
  ⁺² (E^o_{Sn⁺⁴/Sn⁺²}=+0.2 V)

and even

• Cl
  Chlorine
  Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
  
  ^- ( E^o_Cl2/Cl^-=+1.36 V) etc.

In weak acidic medium MnO₄^- can not accept 5 electron

Electron

The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s to form Mn⁺², this time it accepts only 3 electrons and forms MnO₂(s) by the following electrochemical reaction:

MnO₄^- + 4H⁺ + 3e^- = MnO₂ + 2H₂O

The standard potential is E^o=+1.69 V.

For the reaction: MnO₄^- + 8 H⁺ + 5 e^- = Mn²⁺ + 4 H₂O
the standard reduction potential is E^o=+1.51 V.

And if the solution has a concentration

Concentration

In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...

 c_(NaOH)>1 mol dm⁻³ the following reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

occurs:

MnO₄^- + e^- = MnO₄^2- E^o=+0.56 V.