(a) Interpretation: The Ca 2+ concentration in the inner solution of electrode 2 should be determined. Concept introduction: Nernst equation gives the cell potential under non-standard conditions. E = E 0 − 2.303 R T n F log Q E − cell potential E 0 − standard cell potential R − universal gas constant T − temperature in Kelvin n − number of electrons transferred F − Faraday constant Q − Reaction quotient E c e l l = E c a t h o d e 0 − E a n o d e 0

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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 23, Problem 23.27QAP
Interpretation Introduction

(a)

Interpretation:

The Ca2+ concentration in the inner solution of electrode 2 should be determined.

Concept introduction:

Nernst equation gives the cell potential under non-standard conditions.

E=E02.303RTnFlogQ

E − cell potential

E0 − standard cell potential

R − universal gas constant

T − temperature in Kelvin

n − number of electrons transferred

F − Faraday constant

Q − Reaction quotient

Ecell=Ecathode0Eanode0

Interpretation Introduction

(b)

Interpretation:

The ionic strength of the solution in Electrode 2 should be determined.

Concept introduction:

The ionic strength can be calculated as follows:

μ=12(c1Z12+c2Z22+c3Z32+....)

Here,

µ − ionic strength

c − molar concentrations of the ions

Z − charge on the ion.

Interpretation Introduction

(c)

Interpretation:

The activity of Ca2+ in electrode 2 should be determined.

Concept introduction:

The activity of coefficient of species A can be calculated as follows:

logγA=0.509ZA2μ1+3.28αAμ

Here,

γA= activity coefficient of species AZA=Charge on the species Aμ = ionic strength of the solutionαA= the effective diameter of the hydrated ion in nanometers

Interpretation Introduction

(d)

Interpretation:

The cell potential versus the pCa should be plotted and pCa value where the plot deviated more than 5% from linearity should be determined. For the linear portion, the slope and the intercept should be determined.

Concept introduction:

For cations,

Ecell=K0.0592npX

Here,

K − constant

n − number of moles of electrons

X − activity of the cation.

Interpretation Introduction

(e)

Interpretation:

The cell potential versus the pCa should be plotted for electrode 2 and the range of linearity should be determined. For the linear portion, the slope and the intercept should be determined.

Concept introduction:

For cations,

Ecell=K0.0592npX

Here,

K − constant

n − number of moles of electrons

X − activity of the cation.

Interpretation Introduction

(f)

Interpretation:

The reason for the term super-Nernstianto be used for electrode 2 should be discussed.

Concept introduction:

Electrode 2 has an inner solution with low activities of Ca2+.

Interpretation Introduction

(g)

Interpretation:

The cell potential versus the pCa should be plotted and the range of linearity should be determined. For the linear portion, the slope and the intercept should be determined.

Concept introduction:

For cations,

Ecell=K0.0592npX

Here,

K − constant

n − number of moles of electrons

X − activity of the cation.

Interpretation Introduction

(h)

Interpretation:

Electrode 3 is said to have Ca2+ release. This term should be explained.

Concept introduction:

Electrode 3 has an inner solution with higher activities of Ca2+.

Interpretation Introduction

(i)

Interpretation:

The alternative explanations for experimental results given in the article should be described.

Concept introduction:

An electrochemical cell, which is used to make potentiometric measurements with a membrane electrode are known as ion selective electrodes. ISE is highly selective for a specific ion. This selectivity depends on the composition of the membrane. Main component of an ISE is inner reference solution, and outer analyte. The potential is developed at the membrane either by ion exchange process or ion transport process.

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