posted by Tara .
why is this reaction spontaneous?
Mg + 2Cu2+ --> Mg2+ + 2Cu+
Mg2+ + 2e --> Mg E= -2.37 V
Cu2 + e --> Cu+ E= 0.15 V
To find out if a reaction is spontaneous, we calculate E(cell). If E(cell)>0, reaction is spontaneous. If E(cell)<0, reaction is not spontaneous. If E(cell)=0, reaction will proceed until equilibrium is established.
So in this case, E(cell) = E(reduction)-E(oxidation) = 0.15V - (-2.37V) = 2.52V >0 hence reaction is spontaneous.
In this case, Mg is oxidized to Mg2+ as it loses 2 electrons while Cu2+ is reduced to Cu+ as it gains 1 electron.
Hope I helped! (: