Potassium is a member that the an initial group that the periodic table (the element is 19ᵗʰ in the periodic table). By its physical properties, metallic potassium is a soft metal of a silvery white color. Choose other alkaline metals, potassium is quite reactive – so the cannot it is in encountered in a totally free state in nature. It reacts readily with plenty of substances, especially with water (potassium hydroxide creates – “caustic potash”). In air, the metal reacts an extremely rapidly – because that its high reactivity, the metal is save on computer under a layer of kerosene or Vaseline. We can name many different properties and possible chemical reactions that room characteristic because that potassium and its compounds.
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Simple substances that metallic potassium reacts with
Metallic potassium is a an excellent reducer. It easily reacts with numerous simple substances:it reacts violently v water, forming one alkali – potassium hydroxide:
2K + 2H₂O = 2KOH + H₂.it burns in air, forming the potassium superoxide KO₂ (nevertheless, in the main product potassium peroxide K₂O₂ is present):
K + O₂ = KO₂ (the oxide deserve to be obtained indigenous the superoxide by heating it v metallic potassium: KO₂ + K = K₂O).it likewise reacts v other chalcogens (except oxygen):
2K + S = K₂S (in a similar way it reacts through selenium and also tellurium, come conduct the reaction heating as much as 100-200 ᵒC (also 212-392 ᵒF is required).
it forms potassium hydride – one ionic compound the metal with hydrogen – as soon as heated as much as 200-300 ᵒC (also 392-572 ᵒF) through hydrogen:
2K + H₂ = 2KH.it easily reacts with halogens (heating is not required come carry out the reaction):
2K + I₂ = 2KI.
2K + Cl₂ = 2KCl.
Click below for interesting experiments v chlorine.
3K + p = K₃P.
At room temperature, potassium barely reacts with gaseous nitrogen (when potassium hydride is heated in a current the nitrogen, the formation the K₃N nitrides is possible). Through some metals (for example sodium or lead), potassium forms intermetallic compounds – compounds the metals between each other.
Reaction of potassium with complex substances
Potassium reacts v ammonium both on heating and also on cooling – but different substances form:
K + 6NH₃ =
2K + 2NH₃ = 2KNH₂ + H₂ (with gentle heating – 65-105 ᵒC (149-221 ᵒF) – potassium amide forms).
As alkaline metals are in located in the electrochemical series before hydrogen, castle react through acids through a displacement reaction:
K + 2HCl = 2KCl + H₂.
With sulfur and also nitric acids (diluted) potassium reacts differently, displaying prominent reducing properties:8K + 6H₂SO₄ = 4K₂SO₄ + SO₂ + S + 6H₂O;21K + 26HNO₃ = 21KNO₃ + NO + N₂O + N₂ + 13H₂O.
With concentrated sulfuric mountain the reaction takes location as follows:
8K + 5H₂SO₄ = 4K₂SO₄ + H₂S + 4H₂O.
Metallic potassium can be alloyed through its alkali – then potassium oxide forms:
2K + 2KOH = 2K₂O + H₂ (heating takes location at a temperature of approximately 450 ᵒC or 842 ᵒF).
Reaction that potassium hydroxide
Potassium hydroxide KOH is a strong alkali that displays solid basic properties – accordingly, reactions v potassium hydroxide take ar according come a typically basic form. The serves as the main raw material for obtaining metallic potassium without alloys (electrolysis of an alloy that potassium hydroxide is carried out according come a summary equation):
4KOH = 4K + O₂ + 2H₂O.
Like every other bases, KOH reacts through acids through a neutralization reaction, forming salt and water:
KOH + HCl = KCl + H₂O (with hydrochloric acid).
KOH + hello = KI + H₂O (with hydroiodic acid).
If an acid is dibasic (for example H₂SO4) or more, different salts have the right to be obtained depending on the ratio the the reagents:KOH + H₂SO₄ = KHSO₄ + H₂O (with a ratio that reagents that 1:1 potassium hydrosulfate forms);2KOH + H₂SO₄ = K₂SO₄ + H₂O (with a ratio that alkali and also acid of 2:1 potassium sulfate forms).
Salts also kind in the reaction of potassium hydroxide v acidic oxides:
2KOH + SO₃ = K₂SO₄ + H₂O (potassium sulfate).
A reaction through carbon dioxide is possible:
2KOH + CO₂ = K₂CO₃ + H₂O.
With amphoteric oxides, potassium hydroxide creates double salts:2KOH + Al₂O₃ = 2KAlO₂ + H₂O (the product that reaction with aluminum oxide is potassium aluminate).
With amphoteric hydroxides, the reaction might take ar in a solution (complex compounds space formed) or in a flux (the product that reaction is a double salt):Be(OH)₂ + 2KOH = K₂BeO₂ + 2H₂O (potassium beryllate forms);Fe(OH)₃ + KOH = K
Double and complex salt are additionally formed in the reaction of potassium hydroxide through amphoteric metals:2KOH + Zn = K₂ZnO₂ + H₂;2KOH + 2Al + 2H₂O = 2KAlO₂ + 3H₂;2KOH + 2Al + 6H₂O = 2K
If as a result that the reaction, one insoluble compound forms, potassium hydroxide can likewise react with salts:
2KOH + CuSO₄ = K₂SO₄ + Cu(OH)₂ (copper (II) hydroxide – a base that is insoluble in water).
Potassium salts behave in a similar means – v other salts the reaction takes location if one insoluble compound forms, as in the reaction of potassium hydroxide through potassium phosphate: 2K₃PO₄ + 3Ca(OH)₂ = Ca₃(PO₄)₂ + 6KOH.
Alkalis likewise react through halogens according come the equation 2KOH + Cl₂ = KClO + KCl + H₂O (KClO – potassium hypochlorite). This reaction takes place at a cold temperature. Top top heating, potassium chlorate forms:
6KOH + 3Cl₂ = KClO₃ + 5KCl + 3H₂O.
With phosphorus the following reaction takes place:
4Р + 3KOH + 3Н₂О = РН₃ + 3KН₂РО₂ (a disproportionation reaction takes ar – phosphorus both oxidizes and reduces).
In some cases, potassium hydroxide serves together a medium for conducting a reaction v potassium permanganate:
2KMnO₄ + K₂SO₃ + 2KOH = K₂SO₄ + 2K₂MnO₄ + H₂O (potassium manganate through the formula K₂MnO₄ deserve to only it is in obtained in the presence that an alkali).
Reactions that metallic potassium and also its hydroxide through organic compounds
Metal is capable that reacting with some organic compounds. For example, the basis of the Wurtz synthesis is the reaction between haloalkenes and also alkaline metals. With this reaction, we have the right to obtain much longer chains that hydrocarbons from shorter ones:
2K + 2CH₃Cl = C₂H₆ (CH₃-CH₃) + 2KCl (this is an example that the symmetrical Wurtz synthesis, together the exact same haloalkene is offered as the reagent – accordingly, the product has a symmetrical structure).
When different haloalkanes space “linked” together the products space different – the Wurtz synthesis have the right to take place both symmetrically and asymmetrically):
6K + 3CH₃Cl + 3C₂H₅Cl = CH₃-CH₃ + CH₃-C₂H₅ (asymmetric product) + C₂H₅-C₂H₅ + 6KCl.
With alcohols, metallic potassium reacts with the formation of alcoholates:
2C₂H₅OH + 2K = 2C₂H₅OK + H₂ (potassium ethylate).
Potassium hydroxide has actually found vast application in reactions that nucleophilic substitution and elimination of halogen derivatives:with an aqueous solution of potassium hydroxide, a nucleophilic substitution take away place, as soon as an atom that halogen in a halogen derivative is substituted to the OH-group:
CH₃-CH₂-Br + KOH(aqueous) = CH₃-CH₂-OH + KBr (ethyl alcohol is obtained native bromic ether);with an alcohol solution the alkali, the reaction takes ar differently: owing come the breaking off of atoms of the halogen and also hydrogen from neighboring (frequently) atoms of carbon, an alkene is created – a hydrocarbon through a double bond:
CH₃-CH₂-Br + KOH(alcohol) = CH₂=CH₂ + KBr + H₂O (ethylene forms). This is an elimination reaction.
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Potassium has found vast application in organic synthesis, because that the manufacture of fertilizers and insulation materials. Potassium compounds (mainly hydroxide and salts) are supplied in electroplating, catalysis, manufacture the food products, detergent bases and dyes.