2 marksShort AnswerSection A

What happens when an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride ? State the physical conditions of reactants in which the reaction between them will not take place. Write the balanced chemical equation for the reaction and name the type of reaction.

Q: What happens when an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride ? State the physical conditions of reactants in which the reaction between them will not take place. Write the balanced chemical equation for the reaction and name the type of reaction.

When an aqueous solution of sodium sulphate ($Na_2SO_4$) reacts with an aqueous solution of barium chloride ($BaCl_2$), a white precipitate of barium sulphate ($BaSO_4$) is formed immediately along with a solution of sodium chloride ($NaCl$). ### Physical Condition for Non-Reaction: The reaction will **not** take place if both reactants are in their **solid state** (dry powders). In the solid state, the ions are held tightly in their crystal lattices and cannot move or exchange with each other. ### Balanced Chemical Equation: $$Na_2SO_4(aq) + BaCl_2(aq) \rightarrow BaSO_4(s) + 2NaCl(aq)$$ ### Type of Reaction: This is a **double displacement reaction** (specifically, a **precipitation reaction**).

Chemical Reactions and Equations

Double Displacement Reaction

Official Answer

When an aqueous solution of sodium sulphate ( $Na_2SO_4$ ) reacts with an aqueous solution of barium chloride ( $BaCl_2$ ), a white precipitate of barium sulphate ( $BaSO_4$ ) is formed immediately along with a solution of sodium chloride ( $NaCl$ ).

Physical Condition for Non-Reaction:

The reaction will not take place if both reactants are in their solid state (dry powders). In the solid state, the ions are held tightly in their crystal lattices and cannot move or exchange with each other.

Balanced Chemical Equation:

$Na_2SO_4(aq) + BaCl_2(aq) \rightarrow BaSO_4(s) + 2NaCl(aq)$

Type of Reaction:

This is a double displacement reaction (specifically, a precipitation reaction).

white precipitatebarium sulphatesolid statedouble displacementprecipitationNa2SO4BaCl2BaSO4NaCl

Marking Scheme

10.5 marks for describing the formation of a white precipitate of barium sulphate.
20.5 marks for stating that the reaction will not occur in the solid state.
30.5 marks for writing the correct balanced chemical equation with state symbols.
40.5 marks for identifying the reaction as a double displacement / precipitation reaction.

Hint

Think about what happens when ions exchange partners. Remember that ions need a medium (like water) to move and interact; they cannot do so in a rigid solid lattice.

Quick Oral Answer

When sodium sulphate and barium chloride solutions are mixed, a white precipitate of barium sulphate is formed. This is a double displacement reaction. It won't happen in the solid state because ions cannot move and exchange without a solvent like water.

Analysis & Explanation

In this reaction, there is an exchange of ions between the reactants. The sodium ions ( $Na^+$ ) pair with chloride ions ( $Cl^-$ ) to form soluble sodium chloride, while the barium ions ( $Ba^{2+}$ ) pair with sulphate ions ( $SO_4^{2-}$ ) to form insoluble barium sulphate, which precipitates out as a white solid.

For any ionic reaction to occur, the ions must be free to move. In the solid state, the electrostatic forces of attraction keep the ions fixed in position, preventing any exchange. Dissolving them in water (forming aqueous solutions) breaks these lattice forces, allowing the ions to move freely and react.

Common Mistakes

1Forgetting to write the state symbols in the chemical equation, especially $(s)$ for the precipitate.
2Stating that the reaction won't happen at high temperatures instead of mentioning the solid state.
3Balancing the equation incorrectly, such as writing $NaCl_2$ or $Na_2Cl$ instead of $2NaCl$ .

Interesting Facts

Barium sulphate is highly insoluble in water and is used as a radiocontrast agent (known as a 'barium meal') for X-ray imaging of the gastrointestinal tract because it is non-toxic due to its insolubility.

Precipitation reactions are widely used in wastewater treatment to remove dissolved heavy metals by precipitating them out as insoluble solids.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2010?

This question carries 2 marks in the CBSE Class 10 Science 2010 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Double Displacement Reaction" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2010 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2010 paper.