Classify Physical/Chemical Change: Na2SO4 + BaCl2 MCQs Quiz | Class 9
Class: IX, Subject: Science (Code 086), Unit: Practicals (Unit I). This quiz covers the reaction between Sodium Sulphate and Barium Chloride, focusing on double displacement reactions, precipitate formation, and classifying physical vs chemical changes. Submit your answers to check your score and download the PDF solution key.
Overview of the Reaction
The reaction between Sodium Sulphate (Na2SO4) and Barium Chloride (BaCl2) is a classic example used in Class 9 Science practicals to demonstrate a chemical change. When aqueous solutions of these two salts are mixed, they undergo a double displacement reaction.
The Chemical Equation:
Na2SO4(aq) + BaCl2(aq) -> BaSO4(s) + 2NaCl(aq)
Key Observations
- Formation of Precipitate: An insoluble white substance (precipitate) is formed immediately upon mixing the clear solutions.
- Identity of Precipitate: The white solid is Barium Sulphate (BaSO4).
- Filtrate: The liquid remaining contains dissolved Sodium Chloride (NaCl).
- Classification: This is a Chemical Change because new substances with different chemical properties are formed, and the reaction is practically irreversible under normal conditions.
Concept: Double Displacement Reaction
In this reaction, the cations (Na+ and Ba2+) and anions (SO4 2- and Cl-) exchange partners. Barium pairs with Sulphate to form insoluble Barium Sulphate, while Sodium pairs with Chlorine to remain in the solution as Sodium Chloride.
Comparison Table
| Aspect | Reactants | Products |
|---|---|---|
| State | Aqueous (Liquid) | Solid (Precipitate) + Aqueous |
| Color | Colorless/Transparent | White (Precipitate) |
| Chemical Nature | Salts | New Salt + Precipitate |
Law of Conservation of Mass
This experiment also verifies the Law of Conservation of Mass. If you weigh the reactants before mixing and the products after mixing (in a closed system), the total mass remains exactly the same, confirming that mass is neither created nor destroyed during a chemical reaction.
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