Answer to Question #184597 in General Chemistry for Aich80

Question

A cell using Zn/Zn+2 (aq, 1M) and H₂ / H⁺¹ (aq, 1M) generates a cell potential of + 0.67 V under standard conditions.

A. Write the half-cell reaction at the anode.

B. Write the half-cell reaction at the cathode.

C. Write the electrochemical cell notation.

D. Calculate the standard reduction potential at the anode.

Answer 1

Write the anode and cathode reactions for a galvanic cell that utilizes the reaction

Ni(s)+2Fe3+→Ni2+ + 2Fe2+

Ni(s)+2Fe3+→Ni2++2Fe2+

Solution

Oxidation takes place at the anode, and the electrode must be Ni|Ni

2+Ni|Ni2+, Ni(s)→Ni2+(aq)+2e−

Ni(s)→Ni(aq)2+ + 2e−

and the reduction occurs at the cathode: 

Fe3+ ,Fe2+ Fe3+, Fe2+:

2Fe3+ +2e−→2Fe2+

2Fe3++2e−→2Fe2+

For every Ni

Ni atom oxidized, two Fe3+

Fe3+ ions are reduced. The electrons from the Ni

Ni metal will flow from the anode, pass the load, and then carry out the reduction at the surface of the cathode to reduce the ferric (Fe3+ Fe3+) ions to ferrous ions. In the meantime the ions in the solution move accordingly to keep the charges balanced.

Discussion

The galvanic cell is:

Ni(s)|Ni

2+ (aq) ||Fe3+(aq) ,Fe2+(aq)|Pt(s)

Ni(s)|Ni(aq)2+||Fe(aq)3+,Fe(aq)2+|Pt(s)

where "Fe3+(aq),Fe2+(aq)

Fe(aq)3+,Fe(aq)2+" represents a solution containing two types of ions. An inert Pt

Pt electrode is placed in the solution to provide electrons for the reduction.