A voltaic cell is constructed from a standard Pb 2+ | Pb half cell (E° red = -0.

Question

A voltaic cell is constructed from a standard Pb2+|Pb half cell (E°red= -0.126V) and a standard Fe3+|Fe2+ half cell (E°red = 0.771V).

(Use the lowest possible coefficients. Use the pull-down boxes to specify states such as (aq) or (s). If a box is not needed, leave it blank.)

The anode reaction is:

The cathode reaction is:

The spontaneous cell reaction is:

The cell voltage is ____ V.

A voltaic cell is constructed from a standard Pb2+|Pb half cell (E°red= -0.126V) and a standard Cd2+|Cd half cell (E°red = -0.403V).

The anode reaction is:

The cathode reaction is:

The spontaneous cell reaction is:

The cell voltage is_______ V.

Explanation / Answer

remember;

Red cat reduction at cathode

and An ox oxidation at anode

the one which is having higher reduction potential will reduce first;

Fe3+/Fe2+ is having higher reduction potential among the two

Fe3+(aq) + e- -----> Fe2+(aq) cathode

anode

Pb(s) ------>Pb2+(aq) + 2e-

multiply cathode by 2 (done to cancel out electrons)

2Fe3+(aq) + 2e- -----> 2Fe2+(aq)

add anode reaction

Pb(s) ------>Pb2+(aq) + 2e-

Spontaneous cell reaction:

Pb(s) + 2Fe3+(aq) ----------->2Fe2+(aq) + Pb2+(aq)

cell voltage = 0.77V -(-0.126V) = 0.896 V

b)

here Pb reduction potential is more and it will serve as cathode contrary to part a

Pb2+(aq) + 2e- ---------> Pb(s) cathode

Cd(s) --------> Cd2+(aq) + 2e- anode

add both of them to get spontaneous cell reaction

Pb2+(aq) + Cd(s) ------->Cd2+(aq) + Pb(s)

cell voltage = -0.126 V -(-0.403V) = 0.277 V

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