Question

1. Reaction of l- with Fe3+ in acidic and basic solution a. Kl(aq) + FeCl3(aq) (ACIDIC) • Observations • Reduction Half Reaction • Oxidation Half Reaction • Overall Balanced Redox Reaction • Explain occurrence or non-occurrence of reaction by calculating Ecell.
What is the reduction half reaction, oxidation half reaction, overall balanced redox reaction, and the occurence/non-occurebce of reaction?

Answer 1

Answer:

The reaction of I^- with Fe³⁺ in acidic medium

The iodide is oxidised to iodine and Fe³⁺ is reduced to Fe²⁺

Thus the reduction half reaction is

      Fe³⁺ + 1 e^-$\rightarrow$ Fe²⁺   ------------------ (1)

The oxidation half reaction is

    2 I^-$\rightarrow$ I₂ + 2 e^- --------------- (2)

The overall reaction is obtained by multiplying equation (1) by 2 and add to equation (2)

[ This is to balance the number of electrons on both sides.]

2 Fe³⁺ + 2 I^-$\rightarrow$ I₂ + 2 Fe²⁺ ------------------ (3)

This equation (3) is the balanced overall redox reaction

It can be expressed in cell notation as

/oxidation//reduction/            or     /anode cell//cathode cell/

that is 2I^- / I₂   //   Fe³⁺ / Fe²⁺

                               anode    cathode

                             (oxidation)     ( reduction)

E⁰_cell = E_ox (anode) + E_red (cathode)

        From the standard reduction potential table

                                        the reduction potential for I₂ + 2 e^-$\rightarrow$ 2I^-       E = 0.54 V

                               Therefore the oxidation potential = -0.54 V

                the reduction potential for Fe³⁺ + e^-$\rightarrow$ Fe²⁺   E = 0.77 V

Therefore E⁰_cell = -0.54 + 0.77 = + 0.23 V

           

Since E⁰_cell is positive , $\Delta$G⁰ = -nFE⁰ will be negative and hence the forward reaction is spontaneous.

E⁰_cell for the reverse reaction is -0.23 V

Since E⁰_cell is negative , $\Delta$G⁰ = -nFE⁰ will be positive and hence the reverse reaction is non-spontaneous.

Thus the reaction

                                 2 Fe³⁺ + 2 I^-$\rightarrow$ I₂ + 2 Fe²⁺ (feasible)

                                  I₂ + 2 Fe²⁺    $\rightarrow$     2 Fe³⁺ + 2 I^- ( not feasible)

                                 is occurence in the forward direction. The reverse reaction is non-occurence.