1) A voltaic cell is constructed from a standard H + | H 2 half cell (E° red = 0

Question

1)

A voltaic cell is constructed from a standard H+|H2 half cell (E°red = 0.000V) and a standard Sn2+|Sn half cell (E°red = -0.140V).  

The anode reaction is:

The cathode reaction is:

The spontaneous cell reaction is:

The cell voltage is ____ V?

2)

A voltaic cell is constructed from a standard Pb2+|Pb half cell (E°red = -0.126V) and a standard Cr3+|Cr half cell (E°red = -0.740V).  

The anode reaction is:

The cathode reaction is:

The spontaneous cell reaction is:

The cell voltage is ____V?

Explanation / Answer

(1)

The half cell which is having less reduction potential undergoes oxdation at anode and the other undergoes reduction at chatode.

So,

Anode Half Reaction:

Sn (s) ------------> Sn2+ (aq.) + 2 e-

Cathode Half Reaction:

2 H+ (aq.) + 2 e- -----------> H2 (g)

Cell reaction:

Sn (s) + 2 H+ (aq.) -------------> Sn2+ (aq.) + H2 (g)
E0cell = E0cathode - E0anode

E0cell = 0.000 - ( - 0.140) = + 0.140 V

(2)

Anode Half Reaction is,

Cr (s) -----------> Cr3+ (aq.) + 3 e-

Cathode Hlaf Reaction is,

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

Cell reaction:

3 Pb2+ (aq.) + 2 Cr (s) -----------> 3 Pb (s) + 2 Cr3+ (aq.)

E0cell = E0cathode - E0anode

E0cell = - 0.126 - ( - 0.740)

E0cell = + 0.614 V

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