You construct a voltaic cell for the following chemical reaction: Tl3 + (aq) + 2Cr2 + (aq) → Tl + (aq) + 2Cr3 + (aq) The measured cell potential under standard conditions is + 1.19 V. Given that E°red for Cr3 + (aq) | Cr2 + (aq) is - 0.41 V, what is E°red for Tl3 + (aq) | Tl + (aq) ?

E°red for Tl³⁺ (aq) | Tl⁺ (aq) is 0.78 V

Explanation:

According to cell reaction we can predict which one cathode half cell and which one anode.

We know left hand side electrode where oxidation occur acts as an anode and right hand side electrode where reduction take place acts as an cathode.

Hence Cr²⁺ converted into Cr³⁺ since oxidation is take place where as Ti³⁺ converted into Ti⁺ means reduction take place.

Anode half cell is Cr³⁺ (aq) | Cr²⁺ (aq) is E⁰red = - 0.41 V

Cathode half cell is Ti³⁺ (aq) | Ti⁺ (aq) is E⁰red = ?

E⁰cell = E⁰cathode - E⁰anode

⇒ E⁰cathode = E⁰cell + E⁰anode

⇒ E⁰cathode = 1.19 + ( - 0.41) volt = 0.78 V