Potassium Sulfate Formula: NCERT Class 7 Chemistry

Potassium Sulfate Formula: Potassium sulfate is an inorganic compound with the chemical formula \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\). It is also known as sulfate of potash or arcanite or potash of sulfur. Arcanite is the rare, naturally occurring mineral of potassium sulfate. Potassium sulfate is a white solid which has found major use in fertilizers. In this article, we are going to discuss potassium sulfate in detail.

Potassium Sulfate: Chemical Formula

The chemical formula of potassium sulfate is \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\). It contains potassium \(\left( {{{\rm{K}}^ + }} \right)\) and sulfate \(\left( {{\rm{S}}{{\rm{O}}_4}^{2 – }} \right)\) ions. It is considered as an ionic compound. Potassium sulfate can be represented as,

The molar mass of potassium sulfate is \(174.259\;{\rm{g}}/{\rm{mol}}\).

Potassium Sulfate: Chemical Formula Derivation

The chemical formula of potassium sulfate can be derived using the criss-cross method. In the criss-cross method, using the valencies of the individual components, we can write chemical formulas easily. The symbol of the positive or metal ion is written on the left, and the symbol of the negative part is written on the right.

The valency number of the positive part is written as a subscript on the symbol of the negative part, and the valency number of the negative part is written as a subscript on the symbol of the positive part. Subscript one is not often written. Signs of the charges are discarded.

Now, using this, the chemical formula of potassium sulfate can be written as, Potassium sulfate contains potassium \(\left( {{{\rm{K}}^ + }} \right)\) and sulfate \(\left( {{\rm{S}}{{\rm{O}}_4}^{2 – }} \right)\) radicals. The valency of potassium ion is one, and that of sulfate radical is two. By criss-crossing the valencies, we can write the chemical formula of potassium sulfate as \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\). That is,

Potassium Sulfate: Preperation

Potassium sulfate can be prepared using the following methods:

1. By the reaction of Potassium Chloride with Sulfuric acid
   On a large scale, potassium sulfate is produced by the reaction between potassium chloride and sulfuric acid. Initially, it produces an intermediate called potassium bisulfate. That is,
   \({\rm{KCl}} + {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4} \to {\rm{HCl}} + {\rm{KHS}}{{\rm{O}}_4}\)
   The above reaction takes place at room temperature and is exothermic in nature.
   In the final step, potassium bisulfate is again reacted with potassium chloride to form potassium sulfate and hydrogen chloride as the products. The chemical equation for the reaction can be given as,
   \({\rm{KCl}} + {\rm{KHS}}{{\rm{O}}_4} \to {\rm{HCl}} + {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\)
   The above reaction is endothermic in nature.
2. By the Reaction of Potassium Hydroxide with Sulfuric Acid
   Potassium sulfate is formed by the reaction of potassium hydroxide and sulfuric acid. The chemical equation for the reaction can be given as,
   \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4} + 2{\rm{KOH}} \to {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} + 2{{\rm{H}}_2}{\rm{O}}\)
3. By the Reaction of Potassium and Sulfuric acid
   Potassium sulfate is produced when potassium reacts with dilute sulfuric acid. The chemical equation for the reaction can be given as,
   \(2{\rm{K}} + {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4} \to {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} + {{\rm{H}}_2}\)
4. By the Reaction of Potassium Bicarbonate and Sulfuric acid
   Potassium sulfate is also produced when potassium bicarbonate reacts with sulfuric acid. The chemical equation for the reaction can be given as,
   \(2{\rm{KHC}}{{\rm{O}}_3} + {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4} \to {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} + 2{{\rm{H}}_2}{\rm{O}} + 2{\rm{C}}{{\rm{O}}_2}\)

Potassium Sulfate: Properties

Let us discuss the physical and chemical properties of potassium sulfate.

Physical Properties of Potassium Sulfate

1. Potassium sulfate appears as a white solid. It is odourless too.
2. It is readily soluble in water and slightly soluble in glycerol.
3. Potassium sulfate is insoluble in acetone, alcohol and \({\rm{C}}{{\rm{S}}_2}\).
4. The melting point of potassium sulfate is approximately equal to \(1342\;{\rm{K}}\), and its boiling point is approximately equal to \(1962\;{\rm{K}}\).
5. The density of potassium sulfate is \(2.66\;{\rm{g}}/{\rm{c}}{{\rm{m}}^3}\).

Chemical Properties of Potassium Sulfate

Reactions of potassium sulfate:

1. Reaction of Potassium Sulfate with Sulfuric acid
   Potassium bisulfate is formed when potassium sulfate reacts with sulfuric acid. That is,
   \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} + {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\, \to \,2{\rm{KHS}}{{\rm{O}}_4}\)
2. Reaction of Potassium Sulfate with Calcium Chloride
   Potassium sulfate reacts with calcium chloride to form calcium sulfate and potassium chloride. The chemical equation for the reaction can be given as,
   \({\rm{CaC}}{{\rm{l}}_2} + {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\, \to \,{\rm{CaS}}{{\rm{O}}_4} + 2{\rm{KCl}}\)
3. Reaction of Potassium Sulfate with Barium Nitrate
   Potassium nitrate and barium sulfate are formed by the reaction between potassium sulfate and barium nitrate. The chemical equation for the reaction can be given as,
   \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} + {\rm{Ba}}{\left( {{\rm{N}}{{\rm{O}}_3}} \right)_2} \to 2{\rm{KN}}{{\rm{O}}_3} + {\rm{BaS}}{{\rm{O}}_4}\)
   This is an example of a double displacement reaction.
4. Reaction of Potassium Sulfate with Barium Chloride
   Barium sulfate and potassium chloride are produced when potassium sulfate reacts with barium chloride. The chemical equation for the reaction can be given as,
   \({\rm{BaC}}{{\rm{l}}_2} + {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} \to {\rm{BaS}}{{\rm{O}}_4} + 2{\rm{KCl}}\)
   The above reaction is a double displacement reaction.
5. Reaction of Potassium Sulfate with Silver Nitrate
   Silver nitrate reacts with potassium sulfate to form potassium nitrate and silver sulfate. The chemical equation for the reaction can be given as,
   \(2{\rm{AgN}}{{\rm{O}}_3} + {{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4} \to {\rm{A}}{{\rm{g}}_2}{\rm{S}}{{\rm{O}}_4} + 2{\rm{KN}}{{\rm{O}}_3}\)
   This is also an example of a double displacement reaction.

Potassium Sulfate: Uses

Potassium sulfate has many uses. They include:

1. Potassium sulfate is majorly used as a fertilizer.
2. Crude potassium sulfate is used in the manufacture of glass.
3. In artillery propellant charges, potassium sulfate is used as a flash reducer.
4. As potassium sulfate is harder, it is used as an alternative blast media similar to soda in soda blasting.
5. In combination with potassium nitrate, potassium sulfate is used in pyrotechnics to generate a purple flame.
6. Potassium sulfate is used to reduce muzzle flash, blast overpressure and flareback.
7. In medicines, potassium sulfate is used as an osmotic laxative.

Summary

Potassium sulfate, which is also known as sulfate of potash or arcanite, is an inorganic compound with the chemical formula \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\). It can be prepared by the reaction of sulfuric acid on potassium metal, potassium hydroxide, potassium chloride or potassium bicarbonate. It appears as a white solid and is odourless too. It is majorly used as a fertilizer. The other physical and chemical properties and major uses of potassium sulfate are detailed in this article.

Frequently Asked Questions on Potassium Sulfate

Frequently asked questions related to potassium sulfate is listed as follows:

Q. What is the formula of potassium sulfate?
Ans: Potassium sulfate is an inorganic compound with the chemical formula \({{\rm{K}}_2}{\rm{S}}{{\rm{O}}_4}\).

Q. What is potassium sulfate used for?
Ans: Potassium sulfate has got many uses. It is majorly used in fertilizers, used in the manufacture of glass, used as a flash reducer, used as an osmotic laxative, etc.

Q. Is potassium sulfate dangerous?
Ans: Potassium sulfate is an irritant. It can cause skin and eye irritations.

Q. What happens when you put potassium sulfate in water?
Ans: Potassium sulfate is highly soluble in water. Therefore, when we put potassium sulfate in water, it completely dissolves in it.

Q. What does potassium sulfate do for plants?
Ans: Potassium sulfate acts as an excellent source of potassium for plants. This potassium is an essential nutrient required for the proper growth of plants.

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