More negative the value of standard electrode potential of a metal, more active will be the metal and a good reducing agents, This is the reason when a more active metal is placed in a solution of less active metal from the solution.
Metal ➝ Cr Cu Mg Zn Fe Al standard electrode
potential – 0.74, + 0. 34, – 2. 36, – 0.76, – 0.44, – 1.66, so, the order of metals in which they displace each other from the solution of their salts in :
Mg, Zn, Cr, Fe, Cu
(More active) (Least active)