(a) Interpretation: A spreadsheet should be created to calculate the standard electrode potential for the Ag-AgCl electrode. Concept introduction: AgCl(s) + e ⇌ Ag(s) + Cl − H + + e ⇌ 1 2 H 2 (g) Overall equation: AgCl(s) + 1 2 H 2 (g) → Ag(s) + Cl − + H + E c e l l = E c e l l 0 − 0.0592 log γ H + γ C l − c H C l 2 P H 2 1 / 2 Activity coefficient of ions can be calculated by Debye-Huckel equation, − log γ x = 0.509 Z x 2 μ 1 + 3.28 α x μ Z x − charge on the species X μ - ionic strength of the solution α x - the effective diameter of the hydrated ion in nanometers. Ionic strength is defined by the equation, μ = 1 2 ( c 1 Z 1 2 + c 2 Z 2 2 + c 3 Z 3 2 + ..... ) C 1 , C 2 , C 3 − molar concentrations of various ions in the solution Z 1 , Z 2 , Z 3 − charges on the ions. For the electrolyte A m B n , the mean activity coefficient is given by γ ± = ( γ A m . γ B n ) 1 ( m + n )

BuyFind

Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213
BuyFind

Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

Solutions

Chapter 22, Problem 22.18QAP
Interpretation Introduction

(a)

Interpretation:

A spreadsheet should be created to calculate the standard electrode potential for the Ag-AgCl electrode.

Concept introduction:

AgCl(s) + e  Ag(s) + Cl

H+ + e  12 H2(g)

Overall equation: AgCl(s) + 12 H2(g)Ag(s) + Cl + H+

Ecell=Ecell00.0592logγH+γClcHCl2PH21/2

Activity coefficient of ions can be calculated by Debye-Huckel equation,

logγx=0.509Zx2μ1+3.28αxμ

Zx − charge on the species X

μ - ionic strength of the solution

αx - the effective diameter of the hydrated ion in nanometers.

Ionic strength is defined by the equation,

μ=12(c1Z12+c2Z22+c3Z32+.....)

C1, C2, C3 − molar concentrations of various ions in the solution

Z1, Z2, Z3 − charges on the ions.

For the electrolyte AmBn, the mean activity coefficient is given by

γ±=(γAm.γBn)1(m+n)

Interpretation Introduction

(b)

Interpretation:

The values obtained in part (a) for the activity coefficients and standard potential should be compared with those of MacInnes and if there are any differences, a possible reason for the discrepancies should be suggested.

Concept introduction:

AgCl(s) + e  Ag(s) + Cl

H+ + e  12 H2(g)

Overall equation: AgCl(s) + 12 H2(g)Ag(s) + Cl + H+

Ecell=Ecell00.0592logγH+γClcHCl2PH21/2

Interpretation Introduction

(c)

Interpretation:

The mean, standard deviation, 95 % confidence interval, and other useful statistics for the standard potential of the Ag-AgCl electrode should be found by using descriptive statistics function of Excel.

Concept introduction:

AgCl(s) + e  Ag(s) + Cl

H+ + e  12 H2(g)

Overall equation: AgCl(s) + 12 H2(g)Ag(s) + Cl + H+

Ecell=Ecell00.0592logγH+γClcHCl2PH21/2

Interpretation Introduction

(d)

Interpretation:

The analysis results and the quality of the MacInne’s results should be compared and discussed.

Concept introduction:

AgCl(s) + e  Ag(s) + Cl

H+ + e  12 H2(g)

Overall equation: AgCl(s) + 12 H2(g)Ag(s) + Cl + H+

Ecell=Ecell00.0592logγH+γClcHCl2PH21/2

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