Thank you The shorthand notation for an electrochemical cell is shown below. Pt(

Question

Thank you The shorthand notation for an electrochemical cell is shown below. Pt(s) | H_2(1 atm) | H^+(1.0 M || Cu2+ (1.0 M) | Cu(s) Sketch the cell clearly and calculate E degree 25 degree C. Calculate the standard cell potential, E degree, for each of the following reactions and predict whether or not reaction will take place spontaneously under standard conditions: Al(s) + Cr^3+(aq) rightarrow Al^3+(aq) + Cr(s) Ni(s) + Pb^2+(aq) rightarrow Ni^2+(aq) + Pb(s), and; List the oxidizing and reducing agents for both reactions.

Explanation / Answer

8. Data:

Pt (s) | H2 (1 atm) | H+ (1.0 M) || Cu2+ (1.0 M) | Cu (s)

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Answer.

In this case the Copper electrode is the catode, because it increases its mass through cell's operation, as reduction reaction predicts, the semi cell reactions are;

Anode (Oxidation)

H2 (1 atm) ==> 2H+ (1.0 M) + 2e-

Catode (Reduction)

Cu2+ (ac) + 2e- ==> Cu (s)

Overall

H2 (1 atm) + Cu2+ (1M) ==> 2H+ (1.0 M) + Cu (s)

In standard conditions and at 25°C, the cell fem is: +0.34 V, so it can be written like this;

E°cell = E°catode - E°anode

+0.34 V = E°Cu2+/Cu - E°H+/H2

+0.34 V = E°Cu2+/Cu - 0 V

E°Cu2+/Cu = +0.34 V

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9. Data:

Standard cell potentials tables

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Answers.

i. Al (s) + Cr3+ (aq) ==> Al3+ (aq) + Cr (s)

Applying diagonal rule, it's seen that Cr3+ will oxidize Al, the semicell reactions are;

Anode (Oxidation)

Al3+ (aq) + 3e- ==> Al (s)

E° = -1.66 V

Catode (Reduction)

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

E° = -0.74 V

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E°cell = E°catode - E°anode

E°cell = (-0.74 V) - (-1.66 V)

E°cell = +0.92 V

The positive value of E° tells us that cell reaction is spontaneus.

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ii. Ni (s) + Pb2+ (aq) ==> Ni2+ (aq) + Pb (s)

Applying diagonal rule, it's seen that Pb2+ will oxidize Ni, the semicell reactions are;

Anode (Oxidation)

Ni2+ (aq) + 2e- ==> Ni (s)

E° = -0.25 V

Catode (Reduction)

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

E° = -0.13 V

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E°cell = E°catode - E°anode

E°cell = (-0.13 V) - (-0.25 V)

E°cell = +0.12 V

The positive value of E° tells us that cell reaction is spontaneus.

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