Classify Reactions: Displacement MCQs Quiz | Class 10

This quiz covers Class X Science (Code 086), Unit Practicals (Unit I), focusing on Classify Reactions: Displacement MCQs. Specifically, it includes questions related to the reaction involving iron nails in copper sulphate solution. Test your knowledge, then click ‘Submit Quiz’ to see your score and ‘Download Answer PDF’ for a detailed review.

Understanding Displacement Reactions: The Iron and Copper Sulphate Experiment

Displacement reactions are fundamental chemical reactions where a more reactive element displaces a less reactive element from its compound. One classic example illustrating this concept is the reaction between an iron nail and copper sulphate solution. This experiment beautifully demonstrates the principles of reactivity series and single displacement.

What is a Displacement Reaction?

A displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound solution.

General form: A + BC → AC + B

Here, A is more reactive than B.

The Reactivity Series

The reactivity series is a list of metals arranged in decreasing order of their reactivity. A metal higher in the series can displace a metal lower in the series from its salt solution.

A simplified section of the reactivity series:

Potassium > Sodium > Calcium > Magnesium > Aluminium > Zinc > Iron > Lead > Hydrogen > Copper > Silver > Gold

The Iron Nail and Copper Sulphate Solution Experiment

1. Reactants:

  • Iron nail (Fe): A metal.
  • Copper Sulphate solution (CuSO4): A blue colored salt solution of copper.

2. Observation:

  • When an iron nail is dipped in blue copper sulphate solution, after some time:
  • The blue color of the copper sulphate solution starts to fade and eventually changes to a light green color.
  • A reddish-brown deposit is observed on the surface of the iron nail.

3. Explanation:

  • Iron is more reactive than copper (refer to the reactivity series).
  • Because iron is more reactive, it displaces copper from the copper sulphate solution.
  • The iron atoms lose electrons to form iron(II) ions (Fe2+), which then combine with sulphate ions to form iron(II) sulphate. Iron(II) sulphate is light green in color, explaining the color change of the solution.
  • The displaced copper ions (Cu2+) gain electrons and are reduced to copper metal (Cu), which gets deposited as a reddish-brown layer on the iron nail.

4. Chemical Equation:

Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)

Iron (solid) + Copper Sulphate (aqueous, blue) → Iron(II) Sulphate (aqueous, light green) + Copper (solid, reddish-brown)

Key Takeaways:

  • Displacement reactions occur when a more reactive element pushes out a less reactive element from its compound.
  • The reactivity series helps predict whether a displacement reaction will occur.
  • The reaction between iron and copper sulphate is a classic example of a single displacement reaction.
  • Observations: Blue solution to green, reddish-brown deposit on iron.

Quick Revision Points:

  • A + BC → AC + B (if A is more reactive than B)
  • Iron is more reactive than Copper.
  • Copper Sulphate (CuSO4) is blue.
  • Iron(II) Sulphate (FeSO4) is light green.
  • Copper metal is reddish-brown.

Extra Practice Questions:

  1. Why is a new luster observed on the surface of the iron nail after dipping it in copper sulphate solution?
  2. If you dip a copper wire into zinc sulphate solution, would you observe any reaction? Explain why or why not.
  3. Suggest another metal that could displace copper from copper sulphate solution.
  4. What would happen if you dipped an iron nail into ferrous sulphate solution?
  5. How is the concept of oxidation and reduction applied in the reaction between iron and copper sulphate?