Difference Between Ammonia and Ammonium Hydroxide

The key difference between ammonia and ammonium hydroxide is that ammonia occurs as a gas while ammonium hydroxide occurs as a liquid at room temperature.

Ammonia and ammonium hydroxide have many uses for us. We all know that ammonia is a pungent smelling gas with a chemical formula NH3. When it comes in contact with water, what we get is ammonium hydroxide. Therefore, we sometimes name ammonium hydroxide as the “ammonia solution”.

CONTENTS

1. Overview and Key Difference
2. What is Ammonia
3. What is Ammonium Hydroxide
4. Side by Side Comparison – Ammonia vs Ammonium Hydroxide in Tabular Form
5. Summary

What is Ammonia?

Ammonia is a gaseous substance having the chemical formula NH3. It is an inorganic compound and also is the simplest pnictogen hydride. It is a colourless gas but has a pungent, irritating odour. Moreover, the IUPAC name of Ammonia is azane.

Some important chemical facts about this substance are as follows:

• The chemical formula is NH3
• Molar mass is 17.03 g/mol.
• Appears as a colourless gas
• Melting point is −77.73 °C
• Boiling point is −33.34 °C

When considering the occurrence of this compound, it naturally occurs but in trace amounts. That is as a product of nitrogenous animal and vegetable matter. Sometimes, we can find ammonia in rainwater as well. Inside our body, kidneys secrete ammonia to neutralize excess acid.

In the chemical structure of the ammonia molecule, it has a nitrogen atom bound to three hydrogen atoms. Since there are five electrons in the outermost electron shell of nitrogen, there is a lone electron pair on the nitrogen atom of the ammonia molecule. Hence, the geometry of the ammonia molecule is trigonal pyramidal. Furthermore, we can liquefy this compound easily. This is because it is capable of forming hydrogen bonds between ammonia molecules since there are N-H bonds and lone electron pairs as well.

What is Ammonium Hydroxide?

Ammonium hydroxide is a liquid substance having the chemical formula NH₄OH. It is also an inorganic compound. We can call it as ammonia solution because this compound forms when ammonia gas reacts with water. Therefore, we can denote it as NH₃(aq). Though the name ammonium hydroxide implies the existence of an alkaline compound, it is actually impossible to isolate the chemical compound ammonium hydroxide.

 Some important chemical facts about this compound are as follows:

• Chemical formula is NH4OH
• Molar mass is 35.04 g/mol.
• Appears as a colourless liquid.
• It has a highly pungent odour.
• Melting point is −57.5 °C
• Boiling point is 37.7 °C

When considering the applications of this liquid, it is useful as a household cleaner, as an alkyl amine precursor, for water treatment purposes, and many other applications are there.

The reaction for the formation of this compound is as follows:

NH₃ + H₂O —> NH₄₊ + OH^–

What is the Difference Between Ammonia and Ammonium Hydroxide?

Ammonia is a gaseous substance having the chemical formula NH3 whereas ammonium hydroxide is a liquid substance having the chemical formula NH₄OH. Hence, the key difference between ammonia and ammonium hydroxide exists in their physical states. That is, the difference between ammonia and ammonium hydroxide is that ammonia occurs as a gas while ammonium hydroxide occurs as a liquid at room temperature. Since ammonium hydroxide forms when ammonia gas dissolved in water, we call this compound as ammonia solution or liquid ammonia as well. Furthermore, another difference between ammonia and ammonium hydroxide is that ammonia is anhydrous, while ammonium hydroxide is hydrous.

Summary – Ammonia vs Ammonium Hydroxide

Ammonium hydroxide forms from the dissolution of ammonia gas in water. Therefore, ammonium hydroxide actually is an aqueous solution of ammonia. However, the key difference between ammonia and ammonium hydroxide is that ammonia occurs as a gas while ammonium hydroxide occurs as a liquid at room temperature.

Reference:

1. “Ammonia.” Wikipedia, Wikimedia Foundation, 16 Oct. 2018. Available here 
2. “Ammonia Solution.” Wikipedia, Wikimedia Foundation, 17 Oct. 2018. Available here

Image Courtesy:

1.Ammonia-dimensions-from-Greenwood&Earnshaw-2D”By Ben Mills – Own work, (Public Domain) via Commons Wikimedia 
2.”Ammonium-3D-balls”(Public Domain) via Commons Wikimedia