The difference between the displacement and double displacement reactions is that in a displacement reaction one element displaces another by virtue of it being more reactive whereas in a double displacement two anions and two cations switch places between two compounds respectively.
For example:
CuSO4 (aq) + Zn(s) → ZnSO4 + Cu(s)
Blue copper sulphate solution reacting with solid zinc will give rise to colourless zinc sulphate solution and solid copper. Thus Zn displaces Cu in the salt form. Zn is more reactive than Cu.
An example of double displacement reaction is the reaction between sodium carbonate and calcium chloride, both in aqueous
Solution:
Na2CO3 (aq) + CaCl2 (aq) → CaCO3 (ppt) + 2NaCl(aq)
