Manganic acid is an inorganic unstable compound with the formula HMnO4. It cannot be confused with any other substance, as it has a bright, intense purple-red color.
This is a strong electrolyte in which molecules (electrically neutral particles) are almost completely dissociated into ions. Despite the fact that it exists only in solutions, because it has not been obtained as a separate substance. However, you can tell about all its features in more detail.
Chemical properties
In liquids, manganese acid gradually decomposes. This process is accompanied by the release of oxygen (chalcogen, a reactive non-metal).
As a result, a precipitate of manganese dioxide is formed. This is how this process looks like with the participation of manganese acid in the formula: 4HMnO4 → 4MnO2↓+3O2↑+ 2N2O.
The resulting compound is MnO2. Dark brown powder that is insoluble in water. It is the most stable compound of manganese, which belongs to the group of ferrous metals.
Also, the compound in question exhibits features that are common to strong acids. In particular, it enters into neutralization reactions - it interacts with alkalis, forming s alts and water. As a rule, such processes are exometric, that is, they are accompanied by the release of heat. Here is one example: HMnO4 + NaOH → NaMnO4 +H2O.
It is also worth mentioning that permanganic acid, like its permanganates (s alts), is a powerful oxidizing agent, an electron acceptor. Here is an example demonstrating this: 2HMnO4 + 14HCl → 2MnCl2 + 5Cl2↑+ 8H 2O.
Physical properties
As mentioned earlier, permanganic acid, the graphical formula of which is shown above, has not been derived in its pure form. The maximum concentration in aqueous solutions with a characteristic bright lilac color does not exceed 20%.
This substance is sensitive to temperature. If it is less than 20 ° C, then the solution forms a crystalline hydrate - a solid that occurs as a result of the bonding of cations (positively charged ions) and water molecules. Its formula is: HMnO4 ⋅ 2H2O. Ionic structure: (H5O2)+ (MnO4)–.
Also, speaking ofphysical properties of permanganic acid, it is worth noting its molar mass. It is 119.94 g/mol.
Producing acid
Most often, this substance is obtained by carrying out a reaction between two compounds - dilute sulfuric acid and a solution of barium permanganate, an element with high chemical activity. As a result, an insoluble precipitate of its sulfate precipitates. But it is removed by filtering. It looks like this: Va (MnO4) + H2SO4 → 2HMnO 4 + BaSO4↓.
There is another way to get this acid. It is based on the interaction of water and manganese oxide occurring in the cold. This, by the way, is an oily liquid that comes in two shades (brown-green or scarlet). Whatever the color, there will always be a metallic sheen. He is stable at room temperature. And when combined with combustible substances, it ignites them, often with an explosion. So, the reaction formula looks like this: Mn2O7 + H2O → 2HMnO 4.
Dioxide characteristic
This substance, which has already been mentioned above, is found in large quantities in the earth's crust. In the form of a mineral called pyrolusite. Usually black or steel grey. Its crystals are small, columnar or needle-shaped. The mineral has the following properties:
- Piezoelectric. Manifested in the occurrence of dielectric polarization - the displacement of bound charges in it or the rotation of electric dipoles.
- Semiconductor. Manifested as an increase in electrical conductivity with increasing temperature.
It is also worth noting that the dioxide is soluble in hydrochloric acid, which is accompanied by the release of chlorine.
Use of pyrolusite
Electrolytic manganese dioxide has found wide application in the production of batteries and galvanic cells - chemical sources of electric current, which are usually based on the interaction of two metals or their oxides in an electrolyte. Also used for:
- Formation of catalysts - chemicals that speed up the reaction, but are not part of it. A vivid example is hopkalit. They fill additional cartridges for gas masks to protect against carbon monoxide.
- The formation of substances such as manganese s alt and potassium permanganate - dark purple, almost black crystals, which, when dissolved in water, lead to the formation of a bright crimson liquid. Formula - KMnO4.
- Discoloration of green glasses.
- Production of oils and varnishes in the paint and varnish industry.
- For dressing chrome leather in the leather industry.
Interestingly, scientists have determined that pieces of pyrolusite from the Peche de Laze cave in southern France are composed of pure manganese dioxide. It is believed that the Neanderthals, who lived 350-600 thousand years ago, used it as a catalyst and oxidizer for combustion and oxidation reactions.
Permanganate (potassium permanganate)
Many people are familiar with this substance. However, oits application - a little later. It is more important to note that it is with the help of permanganate that many OVR of manganese acid (oxidation-reduction reactions) proceed.
This is due to its exceptional chemical properties. Depending on the hydrogen index (pH) of the solution formed by permanganate, various substances can be oxidized, with reduction to compounds of many oxidation states.
There are many examples. In an acidic environment, reduction to manganese (II) compounds will occur, in a neutral environment it will be equal to (IV), and in a strongly alkaline environment - (VI). Here's what it looks like:
- Acidic: 2KMnO4 +5K2SO3 + 3H 2SO4 → 6K2SO4 + 2MnSO 4 +3N2O.
- B neutral: 2KMnO4 + 3K2SO3 + H 2O → 3K2SO4 + 2MnO2 + 2KOH.
- B alkaline: 2KMnO4 + K2SO3 + 2KOH → K 2SO4 + 2K2MnO4 + H 2Oh. This reaction in this form occurs with a lack of a reducing agent and in the presence of highly concentrated alkali. Such conditions slow down hydrolysis.
It is worth noting that the substance explodes on contact with concentrated sulfuric acid. But if permanganate is carefully combined with this cold substance, unstable manganese oxide is formed.
Using potassium permanganate
The permanganate of the substance in question haspowerful antiseptic action. Particularly widely used in medicine are dilute solutions with a concentration of 0.1%, which I use to treat burns, gargle and wash wounds. It is also an effective emetic for poisoning with alkonides such as aconitine and morphine. Only in such cases, use a less concentrated solution, diluted to 0.02-0.1%.
Pharmacological action is atypical. When the solution comes into contact with organic substances, atomic oxygen is released. The oxide, which is part of it, forms compounds such as albuminates with proteins. In small concentrations, they have an astringent effect, and in large concentrations, they are irritating, tanning and cauterizing. Therefore, the final effect depends on how the permanganate of permanganic acid is diluted - strongly or weakly.
Other applications
Potassium permanganate is actually a substance that is actively used in various fields. In addition to medicine, it is involved:
- When washing laboratory glassware. Excellent for removing fats and organic matter.
- In pyrotechnics as an oxidizing agent.
- When determining permanganate oxidizability in the process of assessing water quality according to GOST 2761-84 (Kubel method).
- When toning photos.
- For wood pickling. The liquid is used as a stain (a substance that gives color).
- For risky tattoo removal. The liquid burns the skin, and the tissues with the paint die off. It hurts and the scars still remain.
- B asoxidizing agent in the process of formation of para- and metaphthalic acids.
Finally, I would like to make a reservation that potassium permanganate is included in the fourth list of precursors of the Russian Standing Committee on Drug Control.
