Mixture vs Compound: Solvent Test MCQs Quiz | Class 9
Class IX Science (Code 086) Unit I: Practicals. This quiz covers the topic of distinguishing between a mixture and a compound using specific chemical tests, focusing on Carbon disulphide as a solvent and behavior comparisons. Test your understanding of these chemical properties, view your score, and download the solution PDF for revision.
Topic Overview: Mixture vs Compound
In Class 9 Science Practicals (Unit I), students learn to distinguish between a mixture of iron filings and sulphur powder and the compound iron(II) sulphide (FeS). The distinction is made based on appearance, magnetic properties, and chemical behavior with solvents like carbon disulphide (CS2) and dilute acids.
Key Concepts
- Appearance: A mixture of iron and sulphur is heterogeneous (grey and yellow particles visible). The compound FeS is a black, homogeneous solid.
- Action of Carbon Disulphide (CS2): CS2 is an organic solvent that dissolves sulphur but not iron.
- In a mixture, sulphur dissolves in CS2 leaving iron filings behind. Upon evaporation, yellow sulphur crystals are recovered.
- In a compound (FeS), neither iron nor sulphur dissolves. The compound remains unaffected.
- Action of Magnet: A magnet can separate iron from the mixture but has no effect on the compound FeS.
- Reaction with Dilute HCl:
- Mixture: Iron reacts to evolve Hydrogen gas (colorless, odorless, burns with a pop sound).
- Compound: FeS reacts to evolve Hydrogen Sulphide (H2S) gas (rotten egg smell).
Comparison Table
| Property | Mixture (Fe + S) | Compound (FeS) |
|---|---|---|
| Composition | Variable ratio | Fixed ratio by mass (7:4) |
| Effect of Magnet | Separates Iron | No effect |
| Solubility in CS2 | Sulphur dissolves | Insoluble |
| Properties | Retains properties of constituents | New properties entirely |
Quick Revision Points
- Mixtures are physically combined; compounds are chemically bonded.
- Formation of FeS requires heating; mixing Fe and S does not.
- Energy is usually absorbed or evolved during compound formation.
- Compounds have sharp melting and boiling points; mixtures do not.
Extra Practice Questions
- 1. Why does a magnet not attract iron from FeS? (Ans: Iron has lost its magnetic property due to chemical bonding).
- 2. What happens if you add CS2 to a test tube containing FeS? (Ans: Nothing happens).
- 3. Which gas is produced when dilute H2SO4 reacts with FeS? (Ans: Hydrogen Sulphide).
- 4. Is the mixture of iron and sulphur homogeneous or heterogeneous? (Ans: Heterogeneous).
- 5. What is the color of the residue left after adding CS2 to the mixture? (Ans: Grey, due to iron filings).
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