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Displacement Reaction

A displacement reaction is a reaction in which a more reactive element pushes out a less reactive element from its compound.

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Student-friendly explanation

This reaction depends on the reactivity series. A more reactive metal can replace a less reactive metal from its salt solution. The same idea also works for some non-metals in special cases.

How to write this in exams

  1. 1

    Start with the exact idea

    A displacement reaction is a reaction in which a more reactive element pushes out a less reactive element from its compound.

  2. 2

    Then show how to use it

    1. Identify the free element and the compound. 2. Compare reactivity. 3. If the free element is more reactive, it displaces another element.

  3. 3

    Add one concrete example

    Iron placed in copper sulphate solution displaces copper.

  4. 4

    Avoid this incomplete answer

    Saying it is double displacement because two substances are involved. That is wrong because only one element is replaced.

Definition

A displacement reaction is a reaction in which a more reactive element pushes out a less reactive element from its compound.

Example

Iron placed in copper sulphate solution displaces copper.

Rule to remember

General pattern: A + BC → AC + B, when A is more reactive than B.

Memory hook

More reactive wins the place.

Examples and method

Worked example

Fe + CuSO4 → FeSO4 + Cu. Iron replaces copper, so it is a displacement reaction.

Method to apply

1. Identify the free element and the compound. 2. Compare reactivity. 3. If the free element is more reactive, it displaces another element.

Diagram support

Show the incoming element replacing the less reactive element in the compound.

How CBSE asks it

Questions often ask for the reaction type when one metal is deposited and another is removed from solution.

Avoid common mistakes

Common confusion

Students often forget that the replacing element must be more reactive than the displaced one.

Common wrong answer

Saying it is double displacement because two substances are involved. That is wrong because only one element is replaced.

Exam tip

Always compare reactivity before naming the reaction. Without reactivity, displacement cannot be decided.

Quick check

An iron nail placed in copper sulphate solution gets a copper coating. What type of reaction is this?

It is a displacement reaction because iron is more reactive and removes copper from the solution.

Answer writing and exam use

1-mark answer

A displacement reaction is a reaction in which a more reactive element pushes out a less reactive element from its compound.

2-mark answer

A displacement reaction is a reaction in which a more reactive element pushes out a less reactive element from its compound. General pattern: A + BC → AC + B, when A is more reactive than B. Iron placed in copper sulphate solution displaces copper.

3-mark answer

This reaction depends on the reactivity series. A more reactive metal can replace a less reactive metal from its salt solution. The same idea also works for some non-metals in special cases. General pattern: A + BC → AC + B, when A is more reactive than B. Fe + CuSO4 → FeSO4 + Cu. Iron replaces copper, so it is a displacement reaction. Questions often ask for the reaction type when one metal is deposited and another is removed from solution. Saying it is double displacement because two substances are involved. That is wrong because only one element is replaced.
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