Potassium sulfide
Encyclopedia
Potassium sulfide is the inorganic compound
with the formula K2S. The colourless solid is rarely encountered, because it reacts readily with water, a reaction that affords potassium bisulfide
(KSH) and potassium hydroxide (KOH).
, and the larger S2− centers occupy the eight-coordinate sites. Li2S
, Na2S
, and Rb2S crystallize similarly.
):
In the laboratory, a number of methods exist. K2S arises from the reaction of potassium and sulfur. In the laboratory, this synthesis is usually conducted by combining a solution of potassium in anhydrous ammonia with elemental sulfur.
Another method of making K2S in laboratory involves the reaction of potassium permanganate
and elemental sulfur:
Sulfide is highly basic, consequently K2S completely and irreversibly hydrolyzes
in water according to the following equation:
For many purposes, this reaction is inconsequential since the mixture of SH− and OH− behaves as a source of S2−. Other alkali metal sulfides behave similarly.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula K2S. The colourless solid is rarely encountered, because it reacts readily with water, a reaction that affords potassium bisulfide
Bisulfide
The bisulfide ion, also called hydrogensulfide or hydrosulfide, is the anion with the formula [HS]− . This species is the conjugate base of hydrogen sulfide and in its turn also dissociates in sulfide:A variety of salts are known, including sodium hydrosulfide and potassium hydrosulfide...
(KSH) and potassium hydroxide (KOH).
Structure
It adopts "antifluorite structure," which means that the small K+ ions occupy the tetrahedral (F−) sites in fluoriteFluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
, and the larger S2− centers occupy the eight-coordinate sites. Li2S
Lithium sulfide
Lithium sulfide is the inorganic compound with the formula Li2S. It crystallizes in the antifluorite motif, described as the salt 2S2–. It forms a solid yellow-white deliquescent powder. In air, it easily hydrolyses to release hydrogen sulfide .- Preparation :Lithium sulfide is prepared by...
, Na2S
Sodium sulfide
Sodium sulfide is the name used to refer to the chemical compound Na2S, but more commonly it refers to the hydrate Na2S·9H2O. Both are colorless water-soluble salts that give strongly alkaline solutions...
, and Rb2S crystallize similarly.
Synthesis and reactions
It can be produced by heating K2SO4 with carbon (cokeCoke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
):
- K2SO4 + 4 C → K2S + 4 CO
In the laboratory, a number of methods exist. K2S arises from the reaction of potassium and sulfur. In the laboratory, this synthesis is usually conducted by combining a solution of potassium in anhydrous ammonia with elemental sulfur.
Another method of making K2S in laboratory involves the reaction of 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...
and elemental sulfur:
- 2 KMnO4 + S → K2S + 2 MnO2 + 2 O2
Sulfide is highly basic, consequently K2S completely and irreversibly hydrolyzes
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
in water according to the following equation:
- K2S + H2O → KOH + KSH
For many purposes, this reaction is inconsequential since the mixture of SH− and OH− behaves as a source of S2−. Other alkali metal sulfides behave similarly.