Quantitative Chemical Analysis
Quantitative Chemical Analysis
9th Edition
ISBN: 9781464135385
Author: Daniel C. Harris
Publisher: W. H. Freeman
Question
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Chapter 17, Problem 17.CE

(a)

Interpretation Introduction

Interpretation:

The cathode potential required to reduce Co2+toCo has to be calculated.

Concept Introduction:

When the electric current is too small, the voltage of cell is given as

E = E(cathode)-E(anode)

E(cathode) is electrode’s potential which is attached to negative terminal of current source.

E(anode) is electrode’s potential which is attached to positive  terminal of current source.

Concentration Polarization:  It is the change in concentration of products and reactants at electrode’s surface unlike they are same in solution.

(a)

Expert Solution
Check Mark

Answer to Problem 17.CE

The cathode potential required to reduce Co2+toCo is -0.700 V

Explanation of Solution

To determine: The cathode potential required to reduce Co2+toCo .

The conversion of cobalt ion into cobalt requires certain cathode potential which s calculated as follows,

Co2++2e-Co(s)Eo=-0.282 VE(cathodeVsS.H.E)  =-0.282 -0.059 162log1[Co2+][Co2+]=1.0×10-6ME=-0.459 VE(cathodeVsS.C.E)=-0.459-0.241=-0.700 V

(b)

Interpretation Introduction

Interpretation:

The cathode potential at which the concentration of cobalt EDTA ion is 1.0μM  has to be calculated.

Concept Introduction:

When the electric current is too small, the voltage of cell is given as

E = E(cathode)-E(anode)

E(cathode) is electrode’s potential which is attached to negative terminal of current source.

E(anode) is electrode’s potential which is attached to positive  terminal of current source.

Concentration Polarization:  It is the change in concentration of products and reactants at electrode’s surface unlike they are same in solution.

(b)

Expert Solution
Check Mark

Answer to Problem 17.CE

The cathode potential at which the concentration of cobalt EDTA ion is 1.0μM is -0.833 V .

Explanation of Solution

To determine: The cathode potential at which the concentration of cobalt EDTA ion is 1.0μM .

The conversion of cobalt EDTA ion into cobalt requires certain cathode potential which is calculated as follows,

Co(C2O4)22-+2e-Co(s)+2C2O42-Eo=-0.474 VE(cathodeVsS.H.E)  =-0.474 V -0.059 162log[C2O42-]2[Co(C2O4)22-]0.241[C2O42-]=0.10M[Co(C2O4)22-]=1.0×10-6ME(cathodeVsS.H.E)  =-0.474 V -0.059 162log1000000.241E=-0.833 V

(c)

Interpretation Introduction

Interpretation:

The cathode potential at which the concentration of cobalt EDTA ion is 1.0μM at pH seven has to be calculated.

Concept Introduction:

When the electric current is too small, the voltage of cell is given as

E = E(cathode)-E(anode)

E(cathode) is electrode’s potential which is attached to negative terminal of current source.

E(anode) is electrode’s potential which is attached to positive  terminal of current source.

Concentration Polarization:  It is the change in concentration of products and reactants at electrode’s surface unlike they are same in solution.

(c)

Expert Solution
Check Mark

Answer to Problem 17.CE

The cathode potential at which the concentration of cobalt EDTA ion is 1.0μM at pH seven is -1.056 V .

Explanation of Solution

To determine: The cathode potential at which the concentration of cobalt EDTA ion at pH seven is 1.0μM .

The conversion of cobalt EDTA ion into cobalt requires certain cathode potential which is calculated as follows,

Co2++2e-Co(s)Eo=-0.282 VFormationConstantforCo(EDTA)2-is2.8×1016Kf=[Co(EDTA)2-][Co2+y4-FFormationConstantofEDTAis0.10Mαy4-=3.8×10-4[Co(EDTA)2-]=1.0×10-6M[Co2+]=9.4×10-19ME =-0.282 V -0.059 162log19.4×10-19-0.241E=-1.056 V

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