Define displacement reaction. An iron knife kept in blue copper sulphate solution turns the blue solution into light green. Explain.

Explanation

**Step-by-Step Solution:**

1. **Definition of Displacement Reaction:**
A displacement reaction is a type of chemical reaction in which a more reactive metal displaces a less reactive metal from its compound. In this reaction, the more reactive metal takes the place of the less reactive metal in the compound, resulting in the formation of a new compound and the release of the less reactive metal.

2. **Observation of the Reaction:**
When an iron knife is placed in a blue copper sulfate (CuSO₄) solution, the color of the solution changes from blue to light green. This indicates that a chemical reaction is taking place.

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