Push out and take its place
Displacement: a more reactive element pushes another one out.
The nail in the blue liquid
A shiny iron nail is left in blue copper sulphate solution. After a while the solution turns pale green and the nail is covered with a reddish-brown coat.
What has happened between iron and copper?
What this lesson covers
The idea
In a displacement reaction an element displaces, or removes, another element from its compound; the displacing element is more reactive than the element it displaces.
The nail in the blue liquid
A shiny iron nail is left in blue copper sulphate solution. After a while the solution turns pale green and the nail is covered with a reddish-brown coat.
What has happened between iron and copper?
- Iron took copper’s place in the compound and pushed the copper out
- Copper took iron’s place in the compound
- Nothing happened between them
Drop it in
First do the NCERT experiment. Then predict each swap: will the metal push the other one out?
The stronger one wins
In a displacement reaction an element displaces, or removes, another element from its compound. The displacing element is more reactive than the element it displaces.
Zinc, iron and lead are more reactive than copper, so each can push copper out of its compound.
- Reaction | Displaces | Pushed out
- Fe + CuSO₄ → FeSO₄ + Cu | Iron | Copper
- Zn + CuSO₄ → ZnSO₄ + Cu | Zinc | Copper
- Pb + CuCl₂ → PbCl₂ + Cu | Lead | Copper
Notes
In a displacement reaction an element displaces, or removes, another element from its compound; the displacing element is more reactive than the element it displaces.
Check yourself
In Zn + CuSO₄ → ZnSO₄ + Cu, which element is displaced (pushed out)?
Lead displaces copper from copper chloride (Pb + CuCl₂ → PbCl₂ + Cu). Which is more reactive?
Will a copper strip displace iron from iron sulphate solution?
- Zinc. Zinc is the one that displaces. It is the more reactive element.
- Copper — correct. Yes! Zinc takes the sulphate and copper is left on its own.
- Sulphate. Sulphate stays in solution. It only changes partner. The element displaced is copper.
- Copper. Copper is the one that gets pushed out, so it is the less reactive one.
- Both are equally reactive. Then neither could push the other out.
- Lead — correct. Yes! The element that displaces is the more reactive one.
- No, copper is less reactive than iron — correct. Yes! The ladder shows iron above copper, so copper cannot push it out.
- Yes, because copper is a metal. Being a metal is not enough. The element must be more reactive than the one it pushes out.
- Yes, copper is heavier. Heaviness does not decide this. Reactivity does.