Question

blue colour of copper sulphate solution disappear when some aluminium powder is added on it

Answer 1

Because Aluminium is more reactive than copper and can replace copper from Copper sulphate.


Hope this helps!

Answer 2

Between aluminium and copper the former is more reactive. So when aluminium powder is added to the copper sulphate solution it displaces copper and forms aluminium sulphate. Copper is left behind. Therefore the blue colour of the copper sulphate solution disappears when aluminium powder is added to it.