Study Guides/Chemistry/Define Displacement Reaction
Study Guide · Chemistry

What is a Displacement Reaction? (Definition and Examples)

In Class 10 Chemistry, one of the most important and visually interesting types of chemical reactions you study is the Displacement Reaction. It is a perfect example of how the 'Reactivity Series' of metals dictates chemical behavior.

Question (Click to Flip)

What is the Reactivity Series?

Answer

It is a vertical list of metals arranged in decreasing order of their chemical reactivity. Potassium and Sodium are at the top (most reactive), while Gold and Platinum are at the bottom (least reactive).

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Key Facts

A displacement reaction will NOT occur if you put a less reactive metal into the salt of a more reactive metal. For example, Silver placed in Copper Sulphate will result in 'No Reaction'.

Metals can also displace Hydrogen gas from acids (e.g., Zinc + Hydrochloric Acid).

1. Definition

A Displacement Reaction (or Single Displacement Reaction) is a chemical reaction in which a more highly reactive element displaces (kicks out and replaces) a less reactive element from its aqueous salt solution.

  • General Formula: $A + BC \rightarrow AC + B$ (Here, element A is more powerful/reactive than element B, so it takes B's place).

2. The Classic Example: Iron and Copper

The most famous textbook example involves putting an iron nail into a blue solution of Copper Sulphate.

  • Reaction: $Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s)$
  • What happens: Iron (Fe) is situated higher on the Reactivity Series than Copper (Cu). Therefore, Iron kicks the Copper out of the solution. The blue color of the solution slowly fades to light green (Iron Sulphate), and a brown coating of pure copper metal forms over the iron nail.

3. The Double Displacement Reaction

There is a second variation called a Double Displacement Reaction. In this, two different compounds completely exchange their ions to form two new compounds. This usually results in the formation of a solid precipitate.

  • Example: $Na_2SO_4(aq) + BaCl_2(aq) \rightarrow BaSO_4(s) \downarrow + 2NaCl(aq)$

Questions and Answers

What is the Reactivity Series?+

It is a vertical list of metals arranged in decreasing order of their chemical reactivity. Potassium and Sodium are at the top (most reactive), while Gold and Platinum are at the bottom (least reactive).

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