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Chemistry

Difference Between Double Salt And Complex Salt

Difference Between Double Salt and Complex Salt

Q: 1. What is the main difference between double salt and complex salt with an example?

Double salts dissociate completely into their constituent ions in water, while complex salts yield both simple ions and a complex ion. For example:Double salt: Mohr’s salt (FeSO₄·(NH₄)₂SO₄·6H₂O) dissociates fully into Fe2+, NH₄+, and SO₄2– ions.Complex salt: Potassium ferrocyanide (K₄[Fe(CN)₆]) releases K+ and [Fe(CN)₆]4– ions upon dissolution.This difference is crucial in class 12 chemistry for understanding coordination compounds and salt behavior in solutions.

Q: 2. How do double salts and complex salts behave in water?

Double salts dissociate completely to give all constituent ions in water, whereas complex salts release a complex ion that does not further dissociate.Double salt (like Mohr’s salt) → yields all simple ions.Complex salt (like K₄[Fe(CN)₆]) → forms complex ions plus simple counter-ions, the complex ion remains intact.This key behavior distinguishes them in chemistry practicals and exam MCQs.

Q: 3. What are some common examples of double and complex salts?

Some important examples include:Double salts:Mohr’s salt (FeSO₄·(NH₄)₂SO₄·6H₂O)Carnallite (KCl·MgCl₂·6H₂O)Potash alum (K₂SO₄·Al₂(SO₄)₃·24H₂O)Complex salts:Potassium ferrocyanide (K₄[Fe(CN)₆])Sodium nitroprusside (Na₂[Fe(CN)₅NO]·2H₂O)Potassium dichromate (K₂Cr₂O₇) (in a broader sense as a polyatomic ion complex)Knowing these examples helps in board exams and NEET/JEE preparation.

Q: 4. Is potassium ferrocyanide a double salt or complex salt?

Potassium ferrocyanide (K₄[Fe(CN)₆]) is a classic example of a complex salt because it contains a complex ion ([Fe(CN)₆]4–) that does not dissociate into simple ions in solution. This feature distinguishes it from double salts in chemistry exams and concept questions.

Q: 6. What is complex salt used for?

Complex salts have a wide range of uses in industry and laboratories:Water treatment and cyanide extraction (potassium ferrocyanide)Medical testing and blood analysis (sodium nitroprusside)Catalysis and colorimetric reagents in labsElectroplating and photographyTheir unique structure and stability make them important in both applied and theoretical chemistry contexts.

Q: 7. What is another name for a complex salt?

Complex salts are also known as coordination compounds or coordination complexes. These names emphasize their central metal ion bonded to ligands in a definite structure, a key topic in class 12 chemistry.

Q: 8. Which of the following is not a double salt but is a complex salt?

Out of common options, potassium ferrocyanide (K₄[Fe(CN)₆]) is not a double salt but a complex salt, because it contains a complex ion and does not dissociate fully into all simple ions in solution.

Q: 9. Can a salt be both a double salt and a complex salt?

A salt cannot be both a double salt and a complex salt simultaneously. Double salts are simple mixtures of two salts that lose their identity in solution.Complex salts contain a complex ion and maintain a specific structure in solution.This distinction is important for exams and chemistry classifications.

Q: 10. Why do double salts ionize completely but complex salts do not?

Double salts ionize completely because their components are held by weak electrostatic forces, which break easily in water.Complex salts have strong coordinate covalent bonds between the central metal ion and ligands, making their complex ions stable and unbreakable under normal conditions.Complete dissociation: Double saltsPartial dissociation with stable complexes: Complex saltsThis property affects their ionization behavior in analytical chemistry.

Comparison Table: Double Salt vs Complex Salt in Chemistry

To differentiate between double salt and complex salt: Double salts are crystalline substances formed by the combination of two different salts through the process of crystallisation. These salts are easily dissociated into their constituent ions when dissolved in water. They possess distinct properties and can exhibit different colours, textures, and solubilities compared to their individual salt components. On the other hand, complex salts are formed when a coordination complex, which consists of a central metal ion surrounded by ligands, combines with one or more simple ions. Complex salts have intricate structures and often exhibit unique chemical and physical properties, such as high stability and catalytic activity. The study of double salt and complex salt plays a crucial role in understanding the behaviour of ions and the formation of various chemical compounds. Read further for more detail.

What is Double Salt?

A double salt in chemistry refers to a crystalline compound formed by the combination of two distinct salts through the process of crystallisation. Unlike a simple mixture of two salts, double salts have a specific stoichiometric ratio between their constituent ions. When dissolved in water, double salts dissociate into their constituent ions, exhibiting different properties compared to the individual salts. These properties include altered solubilities, distinct colours, and unique crystalline structures. Double salts are commonly formed when two salts with similar crystal structures and compatible ion sizes crystallize together, resulting in a compound with enhanced stability and distinctive characteristics. The features of double salt are:

Stoichiometric Ratio: Double salts have a specific stoichiometric ratio between the constituent ions. This ratio remains constant regardless of the conditions, indicating a fixed composition.
Unique Properties: Double salts exhibit properties that are different from the individual salts that form them. These properties may include altered solubilities, distinct colors, and unique crystalline structures.
Crystal Structure: Double salts often have a distinct crystal structure compared to individual salts. This structure arises from the arrangement of the ions within the crystal lattice, resulting in a unique three-dimensional pattern.
Enhanced Stability: Double salts are generally more stable than simple mixtures of salts. The formation of strong ionic bonds between the constituent ions contributes to their increased stability.
Specific Formations: Double salts are typically formed when two salts with similar crystal structures and compatible ion sizes crystallize together. The conditions under which they form, such as temperature and concentration, can influence their composition and properties.
Dissociation: When dissolved in water, double salts readily dissociate into their constituent ions. This dissociation allows for the ions to be separated and interact with other substances in solution.

What is Complex Salt?

A complex salt, also known as a coordination compound, refers to a chemical compound formed by the combination of a central metal ion with one or more ligands. Ligands are molecules or ions that bond to the metal ion through coordinate covalent bonds. The complex salt possesses a unique structure where the ligands surround the metal ion, forming a coordination sphere. These compounds exhibit distinct chemical and physical properties compared to simple salts. Complex salts play a vital role in various chemical reactions, including catalysis, electron transfer processes, and the coordination of metal ions in biological systems. The features of complex salt are:

Coordination Sphere: Complex salts have a central metal ion that is surrounded by ligands forming a coordination sphere. The ligands bond to the metal ion through coordinate covalent bonds, creating a stable complex.
Ligand Exchange: Complex salts often exhibit ligand exchange reactions, where the ligands surrounding the metal ion can be replaced by other ligands.
Color Variation: Complex salts often display vibrant colors due to the presence of transition metal ions in their structures. The absorption and reflection of light by these metal ions result in the observed colors.
Stability: Complex salts generally exhibit higher stability compared to simple salts. The coordination bonds between the metal ion and the ligands are typically stronger than the ionic bonds in simple salts.
Chemical Reactivity: Complex salts can undergo various chemical reactions due to the presence of the central metal ion. These reactions can involve ligand substitution, redox processes, and coordination isomerism, among others.
Catalytic Activity: Many complex salts exhibit catalytic activity, where they can facilitate chemical reactions by providing a favorable environment for the reaction to occur. The metal ion in the complex salt can act as a catalyst, influencing the reaction kinetics.

Differentiate Between Double Salt and Complex Salt

S.No	Category	Double Salt	Complex Salt
1.	Composition	Combination of two different salts	Combination of a central metal ion and ligands
2.	Stoichiometry	Fixed stoichiometric ratio between constituent ions	Variable stoichiometry due to ligand exchange
3.	Dissociation	Dissociates into constituent ions when dissolved	Retains its coordination structure in solution
4.	Properties	Altered solubilities, distinct colours, unique structure	Enhanced stability, specific chemical and physical properties
5.	Crystal Structure	Distinct crystal structure compared to individual salts	Coordination sphere around the central metal ion
6.	Formation	Crystallisation of two salts with compatible structures	Interaction of a metal ion with ligands

These are some of the key difference between double salt and complex salt in the terms of composition, stoichiometry, dissociation, crystal structure, etc.

Summary

A double salt is a compound formed by the combination of two different salts through the process of crystallisation. It contains two or more distinct cations or anions that are held together in the crystal lattice structure. A complex salt, on the other hand, is a compound formed by the coordination of a central metal ion with one or more ligands. The ligands are typically molecules or ions that have lone pairs of electrons, allowing them to form coordinate bonds with the metal ion. Double salts exhibit altered properties, while complex salts possess enhanced stability and unique chemical characteristics.

FAQs on Difference Between Double Salt and Complex Salt

1. What is the main difference between double salt and complex salt with an example?

Double salts dissociate completely into their constituent ions in water, while complex salts yield both simple ions and a complex ion. For example:

Double salt: Mohr’s salt (FeSO₄·(NH₄)₂SO₄·6H₂O) dissociates fully into Fe²⁺, NH₄⁺, and SO₄^2– ions.
Complex salt: Potassium ferrocyanide (K₄[Fe(CN)₆]) releases K⁺ and [Fe(CN)₆]^4– ions upon dissolution.

This difference is crucial in class 12 chemistry for understanding coordination compounds and salt behavior in solutions.

2. How do double salts and complex salts behave in water?

Double salts dissociate completely to give all constituent ions in water, whereas complex salts release a complex ion that does not further dissociate.

Double salt (like Mohr’s salt) → yields all simple ions.
Complex salt (like K₄[Fe(CN)₆]) → forms complex ions plus simple counter-ions, the complex ion remains intact.

This key behavior distinguishes them in chemistry practicals and exam MCQs.

3. What are some common examples of double and complex salts?

Some important examples include:
Double salts:

Mohr’s salt (FeSO₄·(NH₄)₂SO₄·6H₂O)
Carnallite (KCl·MgCl₂·6H₂O)
Potash alum (K₂SO₄·Al₂(SO₄)₃·24H₂O)

Complex salts:

Potassium ferrocyanide (K₄[Fe(CN)₆])
Sodium nitroprusside (Na₂[Fe(CN)₅NO]·2H₂O)
Potassium dichromate (K₂Cr₂O₇) (in a broader sense as a polyatomic ion complex)

Knowing these examples helps in board exams and NEET/JEE preparation.

4. Is potassium ferrocyanide a double salt or complex salt?

Potassium ferrocyanide (K₄[Fe(CN)₆]) is a classic example of a complex salt because it contains a complex ion ([Fe(CN)₆]^4–) that does not dissociate into simple ions in solution. This feature distinguishes it from double salts in chemistry exams and concept questions.

5. How can you distinguish double salt from complex salt experimentally?

Double salts and complex salts can be distinguished using simple ion tests in aqueous solutions:

Double salts release all simple ions; specific ion tests (like for Fe²⁺ or SO₄^2–) will be positive.
Complex salts retain complex ions; free metal ions do not appear on ion tests, as the metal remains bound within the complex.

This practical distinction is often asked in board exams and competitive chemistry questions.

6. What is complex salt used for?

Complex salts have a wide range of uses in industry and laboratories:

Water treatment and cyanide extraction (potassium ferrocyanide)
Medical testing and blood analysis (sodium nitroprusside)
Catalysis and colorimetric reagents in labs
Electroplating and photography

Their unique structure and stability make them important in both applied and theoretical chemistry contexts.

7. What is another name for a complex salt?

Complex salts are also known as coordination compounds or coordination complexes. These names emphasize their central metal ion bonded to ligands in a definite structure, a key topic in class 12 chemistry.

8. Which of the following is not a double salt but is a complex salt?

Out of common options, potassium ferrocyanide (K₄[Fe(CN)₆]) is not a double salt but a complex salt, because it contains a complex ion and does not dissociate fully into all simple ions in solution.

9. Can a salt be both a double salt and a complex salt?

A salt cannot be both a double salt and a complex salt simultaneously.

Double salts are simple mixtures of two salts that lose their identity in solution.
Complex salts contain a complex ion and maintain a specific structure in solution.

This distinction is important for exams and chemistry classifications.

10. Why do double salts ionize completely but complex salts do not?

Double salts ionize completely because their components are held by weak electrostatic forces, which break easily in water.
Complex salts have strong coordinate covalent bonds between the central metal ion and ligands, making their complex ions stable and unbreakable under normal conditions.

Complete dissociation: Double salts
Partial dissociation with stable complexes: Complex salts

This property affects their ionization behavior in analytical chemistry.

11. What are the uses of double salts in daily life and industry?

Many double salts have practical uses, such as:

Potash alum: water purification, dyeing fabrics, and in baking powder
Mohr’s salt: laboratory standard for titration and as a source of Fe²⁺ ions in experiments
Carnallite: source of magnesium in fertilizers

Their simple dissociation makes them useful in various chemical processes.

12. How are double and complex salts tested in the laboratory?

In the laboratory, double salts are identified by their complete ionization, allowing all constituent ions to be detected by standard chemical tests, while complex salts do not give positive tests for all expected simple ions due to the presence of complex ions. This is a key practical distinction for chemistry practical exams.