Question

•A voltaic cell is assembled as follows:

??(?) + 2??(??)+ → ??(??)2+ + 2??(?)

a.Write the half-cell reactions. Determine which is reduction and oxidation.

b.Determine which electrodes do the half-cell reactions take place.

c.Determine the direction of electron flow in the external wire.

d.Determine the direction of ion flow in the salt bridge if the salt bridge contains KNO3(aq).

e.Write the shorthand cell notation for this voltaic cell.

f.Calculate the potential difference of the voltaic cell.

Answer 1

??(?) + 2??(??)+ → ??(??)2+ + 2??(?)
This is the net cell reaction . We can split in to oxidation and reduction half
a)
Oxidation takes place at anode
Reduction takes place at cathode

b) Half reactions are
??(?) → ??(??)2+ + 2e- .. At anode

??(??)+ 2e- → 2??(?) .. At cathode

c)
Electrons are generated at anode will move through external circuit towards cathode

So flow of electrons are from anode to cathode

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d)
In order to maintain charge balance ions will migrate trough salt bridge.Anions will
travel to anode and cations will travel to cathode
So
NO3- ions will travel to anode
and K+ ions will travel to cathode
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e)

Cell can be represented as

Ni(s)|Ni2+(aq)|| Ag+(aq)|Ag(s)

f)
   Ni2+ + 2 e−   ⇌Ni(s)   E0 =−0.25 V
    Ag+ +  e−   ⇌Ag(s)   E0 =+0.80 V  

Cell potential E0cell = Ecathode- Eanode
= +0.80 V - [-0.25 V]
E0cell = + 1.05 V
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