Question

Please use the values in the resources listed below instead of the textbook values. For each reaction listed, determine its standard cell potential (in V) at 25°C and whether the reaction is spontaneous at standard conditions. (a) Co2+ (aq) + Pb(s) Co(s) + Pb2+ (aq) E cell = 0.15x v (b) Co(s) + Mg2+ (aq) cell = -2. 09 Co2+ (aq) + Mg(s) V (c) Ag(s) + CO(NO3)3(aq) AgNO3(aq) + Co(NO3)2(aq) cell = v (d) 2 Al(s) + 3 Cu(NO3)2(aq) → 2 AI(NO3)2(aq) + 3 Cu(s) Bºcell - C v

Answer 1

Sol :-

(a). Given Redox reaction is :

Co²⁺ (aq) + Pb (s) -------------------> Pb²⁺ (aq) + Co (s)

Oxidation-Half cell reaction is :

Pb (s) -------------------> Pb²⁺ (aq) + 2e^- , E⁰_Oxidation = + 0.13 V

Reduction-Half cell reaction is:

Co²⁺ (aq) + 2e^- ------------------->Co (s) , E⁰_Reduction = - 0.28 V

Therefore,

Standard cell potential (E⁰_cell) = E⁰_Oxidation + E⁰_Reduction

E⁰_cell = 0.13 V - 0.28 V

E⁰_cell = - 0.15 V

Because, E⁰_cell = -ve, therefore reaction is non-spontaneous.

Because, ΔG0 = - nFE0cell Here, ΔG0 = Standard change in Gibb's free energy n = Number of electrons exchange and F = Faraday constant = 96500 C If E0cell is +ve, then ΔG0 = -ve and the reaction is non-spontaneous at standard state. If E0cell is -ve, then ΔG0 = +ve and the reaction is spontaneous at standard state. If E0cell is 0, then ΔG0 = 0 and the reaction is equilibrium at standard state.

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(b). Given Redox reaction is :

Co (s) + Mg²⁺ (aq) -------------------> Mg (s) + Co²⁺ (aq)

Oxidation-Half cell reaction is :

Co (s) -------------------> Co²⁺ (aq) + 2e^- , E⁰_Oxidation = + 0.28 V

Reduction-Half cell reaction is:

Mg²⁺ (aq) + 2e^- -------------------> Mg (s) , E⁰_Reduction = - 2.37 V

Therefore,

Standard cell potential (E⁰_cell) = E⁰_Oxidation + E⁰_Reduction

E⁰_cell = 0.28 V - 2.37 V

E⁰_cell = - 2.09 V

Because, E⁰_cell = -ve, therefore reaction is non-spontaneous.

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(c). Given Redox reaction (ionic reaction) is :

Ag (s) + Co³⁺ (aq) -------------------> Co²⁺ (aq) + Ag⁺ (aq)

Oxidation-Half cell reaction is :

Ag (s) -------------------> Ag⁺ (aq) + 1e^- , E⁰_Oxidation = - 0.80 V

Reduction-Half cell reaction is:

Co³⁺ (aq) + 1e^- -------------------> Co²⁺ (aq) , E⁰_Reduction = + 1.82 V

Therefore,

Standard cell potential (E⁰_cell) = E⁰_Oxidation + E⁰_Reduction

E⁰_cell = - 0.80 V + 1.82 V

E⁰_cell = + 1.02 V

Because, E⁰_cell = +ve, therefore reaction is Spontaneous.

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(d). Given Redox reaction (ionic reaction) is :

2 Al (s) + 3 Cu²⁺ (aq) -------------------> 2 Al³⁺ (aq) + 3 Cu (s)

Oxidation-Half cell reaction is :

2 Al (s) + -------------------> 2 Al³⁺ (aq) + 6e^- , E⁰_Oxidation =+ 1.66 V

Reduction-Half cell reaction is:

3 Cu²⁺ (aq) + 6e^- -------------------> 3 Cu (s) , E⁰_Reduction = + 0.34 V

Therefore,

Standard cell potential (E⁰_cell) = E⁰_Oxidation + E⁰_Reduction

E⁰_cell = 1.66 V + 0.34 V

E⁰_cell = + 2.0 V

Because, E⁰_cell = +ve, therefore reaction is Spontaneous.