Comparison Table: Double Salt vs Coordination Compound with Examples
The difference between double salts and coordination compounds is a classic concept in JEE Main Chemistry, often asked for 2–3 mark questions or as MCQs. Both types of compounds involve more than one cation or anion, but their chemical behaviour, ionization in solution, and structural properties are distinct. Recognising these differences helps in qualitative analysis, confidently answering short answer questions, and avoiding classic traps in competitive exams.
Definitions: Double Salt vs Coordination Compound
Double salts are crystalline substances formed by combining two simple salts in a fixed stoichiometric ratio. When dissolved in water, they dissociate completely into their constituent ions, showing the properties of all their ions. A common example is Mohr’s salt: FeSO4(NH4)2SO4·6H2O.
Coordination compounds (also called complex salts) contain a central metal atom or ion surrounded by a set of ligands, bonded via coordinate covalent bonds. In aqueous solution, these complexes retain their identity and do not release all constituent ions. For instance, in K4[Fe(CN)6], [Fe(CN)6]4- ion remains intact.
Key Differences: Table Comparison
| Property | Double Salt | Coordination Compound |
|---|---|---|
| Dissociation in Solution | Dissociates completely into all constituent ions | Complex ion remains intact; does not fully dissociate |
| Identity in Solution | Loses crystalline nature, behaves as mixture of ions | Structural unit remains as a single entity |
| Detection of Ions | All ions (from both salts) detected by usual tests | Some ions (inside complex) not identified by direct tests |
| Bonding Type | No coordinate bonds; simple ionic character | Contains coordinate covalent bonds (metal-ligand) |
| Physical Examples | Mohr’s salt, Potash alum, Carnallite | [Fe(CN)6]4–, [Cu(NH3)4]2+ |
| Nomenclature | Named after both salts | Named after central ion and ligands |
| Use in Analysis | Not used as selective analytical reagents | Used widely in qualitative analysis |
This comparison makes it easy to distinguish between double salt and coordination compound in any exam setting. Use this table for quick revision before JEE Main Chemistry tests.
Examples: Double Salt vs Coordination Compound
- Double Salts:
- Mohr’s salt: FeSO4(NH4)2SO4·6H2O
- Potash alum: KAl(SO4)2·12H2O
- Carnallite: KCl·MgCl2·6H2O
- Coordination Compounds:
- K4[Fe(CN)6] (potassium ferrocyanide)
- [Cu(NH3)4]SO4 (tetraammine copper(II) sulphate)
- [Ag(NH3)2]Cl
For a deeper understanding and more examples, access the Double Salt and Coordination Compound Difference article on Vedantu.
Typical Behaviour in Solution
Double salts (like Mohr’s salt) dissociate fully:
- FeSO4(NH4)2SO4·6H2O → Fe2+ + 2NH4+ + 2SO42–
- All ions react with their normal reagents.
Coordination compounds retain their complex ion in water:
- K4[Fe(CN)6] → 4K+ + [Fe(CN)6]4–
- Fe2+ ion is not available for precipitation directly.
This difference in dissociation is crucial in JEE Advanced qualitative inorganic analysis, especially for test reactions.
Quick Revision Points
- Double salt vs coordination compound: main basis is dissociation and ion identification.
- Double salts behave like a mixture of two salts in water.
- Coordination compounds (complexes) have a fixed structure and unique properties.
- Only double salts show all constituent ions in simple reactions; complexes do not.
- Complexes are key to analytical chemistry, e.g., in detection of metal ions.
JEE Main Pitfalls and Exam Tips
- Do not confuse double salts with compounds having more than one cation (they must lose identity in water).
- Remember that complex salt is a synonym for coordination compound in JEE terminology.
- Common salts like NaCl are not double salts; both ions are simple and available in solution.
- Isomerism, selective precipitation and analytical roles are only seen with complexes.
- Revise classic examples: Mohr’s salt (double salt), potassium ferrocyanide (complex).
Practice Questions for JEE Main
- State two differences between double salts and coordination compounds with examples.
- Write the dissociation equation for KAl(SO4)2·12H2O and K4[Fe(CN)6] in water.
- Which of the following is a double salt: (A) FeSO4(NH4)2SO4·6H2O, (B) [Fe(CN)6]4–, (C) NaCl?
- Explain why all ions are detected in double salts but not in complexes during qualitative analysis.
- Match the following: (i) Potash alum (ii) [Ag(NH3)2]Cl — (a) Double salt (b) Coordination compound.
JEE-Style Summary Notes
- Double salts lose identity in solution, releasing all ions; complexes retain the structural unit.
- Most analytical reagents in salt analysis are coordination compounds, not double salts.
- Use the phrase: "Double salt = mixture of ions, complex = entity in solution."
- Practice distinguishing examples repeatedly—this is a recurring objective question domain.
Where to Go Next?
- Read the Coordination Compounds notes for full NCERT coverage and examples.
- Check your strengths via Coordination Compounds Mock Test practice questions.
- Review Compound and Mixture Differences for foundational clarity.
- An in-depth treatment of double salt and complex salt is also available for fast revision.
- Build on your basics with Basic Concepts in Chemistry Notes and apply your learning across topics.
- Access the Salts – Properties page for more details about simple and mixed salts.
- Explore Ligands and Their Types for deeper insight into complex formation.
- Strengthen analytical chemistry concepts via Principles of Practical Chemistry page on Vedantu.
Mastering the distinction between double salts and coordination compounds forms a foundation for many areas of JEE Main Chemistry, from qualitative analysis to concept-based MCQs. Use Vedantu resources for last-minute revision and to cement the difference between double salt and complex compound for your exam.
FAQs on Difference Between Double Salt and Coordination Compound
1. What is the main difference between double salts and coordination compounds?
Double salts dissociate completely into their constituent ions in solution, while coordination compounds retain their complex ion structure and do not break down into simple ions.
Key differences:
- Double salts lose their identity in solution; coordination compounds do not.
- Double salts show all constituent ions in ion tests; coordination compounds do not.
- Examples: Mohr’s salt (double salt), [Fe(CN)6]3- (coordination compound).
2. Give two examples each of double salts and coordination compounds.
Here are two common examples of each type:
- Double salts:
- Mohr’s salt: FeSO4·(NH4)2SO4·6H2O
- Potassium sodium tartrate (Rochelle salt): KNaC4H4O6·4H2O - Coordination compounds:
- Potassium ferrocyanide: K4[Fe(CN)6]
- Tetraammine copper(II) sulfate: [Cu(NH3)4]SO4
3. How do double salts and coordination compounds behave in aqueous solution?
Double salts ionize completely in aqueous solution, releasing all their constituent ions, whereas coordination compounds do not dissociate into simple ions but retain their complex ion structure.
Key points:
- Double salts give tests for all their ions in solution.
- Coordination compounds do not give tests for the ions inside the coordination sphere.
4. What is a double salt? Explain with formula.
Double salts are crystalline substances formed by the combination of two different salts in a fixed proportion, which lose their identity in solution and completely ionize.
Example:
- Mohr’s salt: FeSO4·(NH4)2SO4·6H2O – It dissociates into Fe2+, NH4+, and SO42- ions in water.
5. Why are some salts called complex salts?
Complex salts (another term for coordination compounds) contain a central metal ion bonded to ligands via coordinate bonds, forming a definite structure that does not dissociate into individual ions in solution.
Key features:
- Retain their identity in water.
- Show characteristic chemical properties.
- Example: K4[Fe(CN)6] (potassium ferrocyanide).
6. What is the difference between double salt and complex salt?
The key difference is that double salts dissociate completely into simple ions in water, while complex salts (coordination compounds) retain their complex ion identity and do not release all constituent ions freely.
Summarized:
- Double salts: Lose identity in solution; give tests for all ions.
- Complex salts: Complex ion remains intact; do not show all simple ions in solution.
7. Do double salts and coordination compounds have any similarities?
Yes, both double salts and coordination compounds are formed by the combination of two or more simple salts in a definite stoichiometric ratio.
Similarities include:
- Both are crystalline solids.
- Both have fixed composition.
- Both may show unique colors.
8. What are some uses of coordination compounds that double salts do not have?
Coordination compounds have several specialized uses not shared by double salts, including:
- Analytical chemistry (as analytical reagents for detection and estimation of metal ions).
- Medical applications (e.g., cisplatin as an anti-cancer drug).
- Photography (e.g., silver complexes).
- Catalysis and colorimetric analysis.
9. Can a compound act as both a double salt and a coordination compound?
No, a compound cannot act as both a double salt and a coordination compound simultaneously.
Reason:
- Double salts dissociate completely to give all constituent ions in solution.
- Coordination compounds retain a distinct complex ion structure.
10. Is common salt (NaCl) a double salt?
Common salt (NaCl) is not a double salt; it is a simple salt composed of sodium and chloride ions.
Double salts require two different simple salts combined in a fixed ratio, which NaCl does not satisfy.
