Mixture vs Compound Preparation MCQs Quiz | Class 9
This Class IX Science (Code 086) quiz covers Unit I Practicals regarding the preparation of mixtures and compounds. Topics include mixing iron filings with sulphur powder, observing heterogeneous mixture properties, heating to form a homogeneous compound (FeS), and testing with magnets, carbon disulphide, and acids. Take the quiz to test your knowledge and download the PDF answer key for revision.
Overview: Mixtures vs Compounds
In this practical, students observe the difference between a physical mixture of two elements (Iron and Sulphur) and a chemical compound formed by heating them. Understanding the distinct properties of mixtures and compounds is a fundamental concept in Class 9 Chemistry.
1. Preparation of the Mixture
When iron filings (grey) and sulphur powder (yellow) are mixed together without heating, they form a heterogeneous mixture. The individual properties of iron and sulphur remain unchanged. For example, iron can still be separated by a magnet.
2. Preparation of the Compound
When the mixture of iron and sulphur is heated strongly in a china dish, a chemical reaction occurs. The mixture glows red hot, and a black mass is formed. This black mass is Iron(II) sulphide (FeS), a compound. It is homogeneous and does not show the properties of its constituents.
Comparison Table
| Property | Mixture (Fe + S) | Compound (FeS) |
|---|---|---|
| Appearance | Grey and yellow particles distinct | Black solid mass |
| Magnet Effect | Iron filings stick to magnet | No effect (Iron is chemically bonded) |
| Solvent (CS2) | Sulphur dissolves | No effect (insoluble) |
| Reaction with Acid | Evolves Hydrogen gas (H2) | Evolves Hydrogen Sulphide gas (H2S) |
Key Observations for Practical Exam
- Gas Identification: Hydrogen gas burns with a pop sound. Hydrogen Sulphide (H2S) smells like rotten eggs.
- Safety with CS2: Carbon disulphide is highly inflammable. It must be kept away from burners.
- Exothermic Reaction: The formation of FeS releases heat, causing the mixture to glow even after removing the flame.
Extra Practice Questions
- Q1: Why does the test tube glow during the heating of iron and sulphur? (Answer: The reaction is strongly exothermic).
- Q2: Can we separate iron from FeS using a magnet? (Answer: No, because iron has lost its magnetic property in the compound).
- Q3: What is the color of the residue left after dissolving the mixture in carbon disulphide? (Answer: Grey, which is the iron).
- Q4: Which gas is evolved when dilute HCl is added to the mixture? (Answer: Hydrogen).
- Q5: Is the composition of the mixture fixed? (Answer: No, mixtures have variable composition).
