Question

Consider figure and answer the question to given below.

1. Redraw the diagram to show the direction of electron flow.
2. Is silver plate the anode or cathode?
3. What will happen if salt bridge is removed?
4. When will the cell stop functioning?
5. How will concentration of Zn²⁺ ions and Ag⁺ ions be affected when the cell functions?
6. How will the concentration of Zn²⁺ ions and Ag⁺ ions be affected after the cell becomes ‘dead’?

Answer 1

1. The cell is: \[\ce{Zn(s) | Zn^{+2} || Ag^{+} | Ag}\]
2. Electron will flow from zinc anode to silver cathode in external circuit. Silver will act as cathode, since its standard reduction potential is greater than that of zinc.
3. Potential will drop to zero if salt bridge is suddenly removed.
4. Cell will stop functioning when it is discharged i.e., when cell potential is zero.
5. Nernst equation for the cell is: 0.059,
   E = `"E"^0 - (0.059)/2 log  (["Zn"^(2+)])/(["Ag"^+]^2)`
   Cell potential will decrease with increase in concentration of [Zn⁺²] while it will increase with the concentration of [Ag⁺].
6. When cell is dead or discharged, E will be zero and the cell will be at equilibrium. Then, concentration of Zn⁺² and Ag⁺ will not change.