Q.Which one of the following is not feasible

Step 1. Section 1.5 states the governing rule: when a MORE reactive metal is added to a solution of a LESS reactive metal's ions, the more reactive metal goes into solution (is oxidised) while the less reactive metal ion is reduced and deposited -- and this only proceeds in the direction that gives a net POSITIVE e.m.f. (ΔG0 = -nFE0 negative).

Step 2. Zinc is more reactive than copper (zinc sits higher/earlier in the reactivity series), so option (a), Zn(s) + Cu2+(aq) -> Cu(s) + Zn2+(aq), IS feasible: the more reactive Zn displaces the less reactive Cu2+.

Step 3. Option (b) is the reverse direction -- copper metal displacing zinc ions -- which would require copper (less reactive) to push zinc (more reactive) out of solution, the wrong way round; this is NOT feasible. …

Rank the reactivity of the metal pair in each option (Zn>Cu, Ag<Cu, Cu<Fe) and check whether the reaction shown has the MORE reactive metal going into solution as required by the electrochemical displacement rule; the on …

• Assuming any pair of a metal and another metal's ion will react in either direction -- displacement only proceeds one way, from the more reactive …