Consider the following reduction processes : Al ^ 3+ +3 e ^ - Al ( s ), E ^ 0 =-1.66 ~V Fe ^ 3+ + e ^ - Fe ^ 2+ , E ^ 0 =+0.77 ~V Co ^ 3+ + e ^ - Co ^ 2+ , E ^ 0 =+1.81 ~V Cr ^ 3+ +3 e ^ - Cr ( s ), E ^ =-0.74 ~V The tendency to act as reducing agent decreases in the order :
A. Al > Cr > Fe ^ 2+ > Co ^ 2+
Reducing agent strength is determined by oxidation potential (opposite sign of reduction potential). Stronger reducing agents have more negative oxidation potentials (easier to oxidize). Oxidation potentials: Al(s) → Al³⁺ has E° = +1.66 V (strongest reducing agent); Cr(s) → Cr³⁺ has E° = +0.74 V; Fe²⁺ → Fe³⁺ has E° = -0.77 V; Co²⁺ → Co³⁺ has E° = -1.81 V (weakest reducing agent). Order of decreasing reducing agent tendency: Al > Cr > Fe²⁺ > Co²⁺.
Related: Chemistry — Electrochemistry · All PYQ Banks