Potassium Nitrate Formula: Potassium Nitrate is an inorganic chemical compound. The formula for potassium nitrate is \({\rm{KN}}{{\rm{O}}_3}.\) It is an alkali metal nitrate. It is an ionic salt containing potassium \(\left( {{{\rm{K}}^ + }} \right)\) and nitrate \(\left( {{\rm{NO}}_3^ – } \right)\) ions. It is commonly known as nitrate of potash, saltpeter (Indian saltpeter) or saltpetre.

Naturally, potassium nitrate occurs as the mineral nitre. Potassium Nitrate is a source of the element nitrogen. Potassium nitrate is odourless and appears as a white solid. Potassium nitrate is also used as a food additive. In this article, we have provided detailed information on the potassium nitrate formula. Continue reading to find out more on the potassium nitrate formula!

Potassium Nitrate Chemical Formula: Overview

The chemical formula of potassium nitrate is \({\rm{KN}}{{\rm{O}}_3}.\) It contains potassium \(\left( {{{\rm{K}}^ + }} \right)\) and nitrate \(\left( {{\rm{NO}}_3^ – } \right)\) ions. There exists an ionic bond between potassium and nitrate ions. Therefore, it is considered as an ionic compound. Potassium nitrate can be represented as,

At room temperature, potassium nitrate has an orthorhombic crystal structure.

The molar mass of potassium nitrate \(\left( {{\rm{KN}}{{\rm{O}}_3}} \right)\) is \(101.1032\,{\rm{g}}/{\rm{mol}}\)

Potassium Nitrate Chemical Formula Derivation

To deduce the chemical formula of potassium nitrate, follow the criss-cross method.

In the criss-cross method, if we know the valency of the elements present in it, we can write its formula. On the left, the symbol of the positive part is written, and the negative part’s symbol is written on the right. The valency number of the positive part is written as the subscript on the symbol of the negative part, and the valency number of the negative part is written as the subscript on the symbol of the positive part. Subscript one is not often written. Signs of the charges are discarded.

Using this, we can write the chemical formula of potassium nitrate as,

Potassium nitrate contains potassium \(\left( {{{\rm{K}}^ + }} \right)\) and nitrate \(\left( {{\rm{NO}}_3^ – } \right)\) radicals. The valency of potassium radical is one, and that of nitrate radical is also one. By criss-crossing these numbers, we can write the chemical formula as \({\rm{KN}}{{\rm{O}}_3}.\) That is,

Preparation of Potassium Nitrate

Potassium nitrate can be prepared using the following methods:

1. By the Reaction between Ammonium Nitrate and Potassium Hydroxide

When ammonium nitrate is treated with potassium hydroxide, potassium nitrate, ammonia and water are formed. The chemical equation for the reaction can be given as,
\({\rm{N}}{{\rm{H}}_4}{\rm{N}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right) + {\rm{KOH}}\left( {{\rm{aq}}} \right) \to {\rm{N}}{{\rm{H}}_3}\left( {\rm{g}} \right) + {\rm{KN}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right) + {{\rm{H}}_2}{\rm{O}}\left( {\rm{l}} \right)\)

2. By the Reaction between Ammonium Nitrate and Potassium Chloride

When ammonium nitrate is treated with potassium chloride, potassium nitrate is obtained. The chemical equation for the reaction can be given as,
\({\rm{N}}{{\rm{H}}_4}{\rm{N}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right) + {\rm{KCl}}\left( {{\rm{aq}}} \right) \to {\rm{N}}{{\rm{H}}_4}{\rm{Cl}}\left( {{\rm{aq}}} \right) + {\rm{KN}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right)\)
The above method will not produce ammonia as the by-product.

3. By the Reaction between Potassium Hydroxide and Nitric Acid

Potassium nitrate is produced when potassium hydroxide is treated with nitric acid. The chemical equation for the reaction can be given as,
\({\rm{KOH}}\left( {{\rm{aq}}} \right) + {\rm{HN}}{{\rm{O}}_3} \to {\rm{KN}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right) + {{\rm{H}}_2}{\rm{O}}\left( {\rm{l}} \right)\)
The above reaction is an example of a neutralization reaction.

4. By the Reaction Between Potassium and Nitric Acid

When potassium is treated with nitric acid, potassium nitrate, ammonium nitrate and water are produced. The chemical equation for the reaction can be given as,
\(8{\rm{K}} + 10{\rm{HN}}{{\rm{O}}_3} \to 8{\rm{KN}}{{\rm{O}}_3} + {\rm{N}}{{\rm{H}}_4}{\rm{N}}{{\rm{O}}_3} + 3{{\rm{H}}_2}{\rm{O}}\)

5. Industrial Preparation of Potassium Nitrate

Potassium nitrate can be prepared on an industrial scale by the reaction between potassium chloride and sodium nitrate. The chemical equation for the reaction can be given as,
\({\rm{NaN}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right) + {\rm{KCl}}\left( {{\rm{aq}}} \right) \to {\rm{NaCl}}\left( {{\rm{aq}}} \right) + {\rm{KN}}{{\rm{O}}_3}\left( {{\rm{aq}}} \right)\)
The above reaction is a double displacement reaction.

What are the Properties of Potassium Nitrate?

The physical and chemical properties of potassium nitrate are given below:

Physical Properties of Potassium Nitrate

Below we will discuss the physical properties of potassium nitrate:

1. Potassium nitrate appears as a white solid. It is odourless too.
2. It is soluble in water, glycerol, and ammonia. It is slightly soluble in ethanol.
3. The melting point of potassium nitrate is \(607\,{\rm{K}},\) and its boiling point is equal to \(673\,{\rm{K}}{\rm{.}}\)
4. The density of potassium nitrate is \(2.109\,{\rm{g}}/{\rm{c}}{{\rm{m}}^3}.\)

Chemical Properties of Potassium Nitrate

Below we will discuss the chemical properties of potassium nitrate:

1. Thermal Decomposition of Potassium Nitrate

At the temperature range between \(823 – 1063\,{\rm{K}},\) when potassium nitrate is heated in presence of oxygen, it decomposes to give nitrite and oxygen. The chemical equation for the reaction can be given as,
\(2\,{\rm{KN}}{{\rm{O}}_3}⇌2\,{\rm{KN}}{{\rm{O}}_2} + {{\rm{O}}_2}\)

2. Reaction of Potassium Nitrate with Sulphuric Acid

Potassium nitrate reacts with concentrated sulphuric acid to form nitric acid vapours and potassium bisulphite. The chemical equation for the reaction can be given as,
\({\rm{KN}}{{\rm{O}}_3} + {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4} \to {\rm{KHS}}{{\rm{O}}_4} + {\rm{HN}}{{\rm{O}}_3}\)

3. Reaction of Potassium Nitrate with Sodium Chloride

Potassium nitrate reacts with sodium chloride to form sodium nitrate and potassium chloride. The chemical equation for the reaction can be given as,
\({\rm{NaCl}} + {\rm{KN}}{{\rm{O}}_3} \to {\rm{KCl}} + {\rm{NaN}}{{\rm{O}}_3}\)

4. Potassium nitrate reacts explosively with reducing agents. However, it is not explosive on its own.

Uses of Potassium Nitrate

Potassium Nitrate has various uses. Some of the uses of potassium nitrate are listed below:

1. Potassium nitrate is used for the production of nitric acid by combining it with sulphuric acid.
2. In black powder, potassium nitrate is used as an oxidiser.
3. Potassium nitrate is used as an ingredient during meat processing.
4. It is used as a food additive.
5. In fertilizers, potassium nitrate is used as a source of potassium and nitrogen.
6. It is used in toothpaste for treating sensitivity.
7. It is used for the treatment of asthma.
8. It is used as an ingredient in kidney tablets used for the treatment of pyelitis and urethritis.
9. It was used as a hypotensive too.
10. Potassium nitrate is used as an electrolyte in salt bridge.
11. It is used as an active ingredient in condensed aerosol fire suppression systems.
12. It is used in the heat treatment of metals as a molten salt bath.
13. It is used to induce the flowering of mango trees.
14. In Rocket candy (a model rocket fuel), potassium nitrate is used as an oxidizer.
15. In the chemically strengthened glass, potassium nitrate is used as a source of potassium ions.

Summary

Potassium Nitrate is an ionic salt with the chemical formula \({\rm{KN}}{{\rm{O}}_3}.\) It contains potassium \(\left( {{{\rm{K}}^ + }} \right)\) and nitrate \(\left( {{\rm{NO}}_3^ – } \right)\) ions. It is an ionic compound and appears as a white solid. It can be prepared by the action of ammonium nitrate on potassium hydroxide or potassium chloride. On a large scale, it can be prepared by the reaction between potassium chloride and sodium nitrate.

Potassium nitrate has uses in many industries. It is used in the production of nitric acid by combining it with sulphuric acid. It is also used as an oxidizer in black powder. Potassium nitrate is also used as an ingredient during meat processing.

FAQs

Q1. What is the formula of potassium nitrate?
Ans: Potassium nitrate is an inorganic chemical compound with the formula \({\rm{KN}}{{\rm{O}}_3}.\)

Q2. What is the common name of potassium nitrate?
Ans: The common name of potassium nitrate is Saltpetre (or Indian Saltpetre) or nitrate of potash.

Q3. What do you use potassium nitrate for?
Ans: Potassium nitrate has many uses. The major uses of potassium nitrate are found in fertilizers, rocket propellants, tree stump removal and fireworks.

Q4. Can potassium nitrate kill you?
Ans: Yes, a fatal dose of \(30\) to \(35\,{\rm{grams}}\) of potassium nitrate ingested in a single dose can kill us.

Q5. Is potassium nitrate legal to buy?
Ans: As potassium nitrate, itself is not an explosive, no license or legal permission is needed to buy potassium nitrate.

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