Difference Between Double Salt and Coordination Compound

Key Difference – Double Salt vs Coordination Compound
 

The key difference between double salt and coordination compound is that a double salt contains two salts with different crystal structures whereas a coordination compound contains a central metal ion surrounded by molecules or ions known as ligands.

A double salt is a mixture of two forms of salt compounds. These two salt compounds have two different crystal structures. A coordination compound or a coordination complex contains a central metal ion bonded to one or more ligands via coordinate covalent bonds, forming a complex structure.

CONTENTS

1. Overview and Key Difference
2. What is Double Salt
3. What is Coordination Compound
4. Similarities Between Double Salt and Coordination Compound
5. Side by Side Comparison – Double Salt vs Coordination Compound in Tabular Form
6. Summary

What is Double Salt?

A double salt is a crystalline salt having the composition of a mixture of two simple salts but with a different crystal structure from either. A double salt contains more than one cation or anion because all the salts are composed of anions and cations. The double salt has the two different salt compounds crystallized in the same ionic lattice. This ionic lattice is a regular structure of ions.

Alum is a common example of a double salt. It contains aluminium cations and sulphate anions. A double salt crystallizes as a single salt compound but ionizes as two different salt compounds when dissolved in water. other examples of double salts include potassium sodium tartrate, aluminium sulfacetate (contains two distinct anions), etc.

When a double salt is dissolved in water, it completely ionizes into aqueous ionic species. For example, KCeF₄ is a double salt, and it gives K⁺ ions, Ce³⁺ ions and F^– ions when it is dissolved in water. the properties of the double salt are different from that of individual salt compounds from which the double salt is made of.

What is Coordination Compound?

Coordination compounds are complex structures composed of a central metal ion surrounded by molecules or ions known as ligands. These ligands are bonded to the central metal ion via coordinate covalent bonds. The central metal ion always has a positive charge. The ligands are rich with lone electron pairs. These electrons are donated to the metal ion in order to reduce the positive charge on the metal ion. This type of bonding is known as a coordinate bond.

Coordinate complexes have diverse structures based on the type of metal ion and the number of ligands present in the coordination complex. The structure of the coordination compound is determined by the coordination number of the complex compound. Coordination number is the number of ligands bound to the metal ion. Most of the times, the coordination number of a coordination compounds lies between 2 – 9. There are several structures (also known as geometries) found in coordination compounds as follows.

1. Linear structure – two ligands
2. Trigonal planar – three ligands are bound to the metal ion
3. Tetrahedral or square planar – four ligands
4. Trigonal bipyramidal – five ligands can be found around the metal ion
5. Octahedral – six ligands present
6. Pentagonal bipyramidal – seven ligands
7. Square antiprismatic – eight ligands present

Almost all the coordination compounds have different colours based on the oxidation state of the central metal ion. Oxidation state is the number of electrons that have been removed from the metal atom. these colours are a result of the electronic transitions between atomic orbitals of the metal atom due to light absorption. For example, almost all the copper compounds have a blue or blue-green colour and ferric (Fe³⁺) compounds have a brown colour whereas ferrous (Fe²⁺) compounds have a green colour.

What are the Similarities Between Double Salt and Coordination Compound?

• Both Double Salt and Coordination Compound are complex compounds
• Both Double Salt and Coordination Compound contain many ions (anions and cations)

What is the Difference Between Double Salt and Coordination Compound?

Summary – Double Salt vs Coordination Compound

Double salts and coordination compounds are complex compounds. Double salt is a mixture of two different salt compounds that are crystallized in the same crystal lattice. Coordination compounds are soluble complexes. The difference between double salt and coordination compound is that a double salt contains two salts with different crystal structures whereas a coordination compound contains a central metal ion surrounded by molecules or ions known as ligands.

Reference:

1.“Coordination Complex.” Wikipedia, Wikimedia Foundation, 27 Mar. 2018. Available here 
2.“Double Salt.” Wikipedia, Wikimedia Foundation, 17 Feb. 2018. Available here  
3.Libretexts. “Coordination Compounds.” Chemistry LibreTexts, Libretexts, 19 Jan. 2018. Available here

Image Courtesy:

1.’Mohrs zout’By Capaccio – Own work, (CC BY-SA 3.0) via Commons Wikimedia  
2.’Trans-dichlorotetraamminecobalt(III)’By Benjah-bmm27 – Own work, (Public Domain) via Commons Wikimedia