Homework Help
Homework Help
View Details
Assignment Help
Assignment Help
View Details
Online Tutoring
Online Tutoring
View Details
Home » Chemistry Homework Help » Physical Chemistry » Ion Selective Electrodes
Ion Selective Electrodes
An ion selective membrane can be used to form an electrochemical cell whose emf depends on the concentration of that ion.

Before we proceed to an important application of emf measurements, brief mention should be made of a component of the most common electrochemical instrument, the glass electrode. Fig indicates the electrode assembly of a pH meter, which includes a typical glass electrode. The electrode, not the cell, usually consists of the arrangement:

Ag |AgCl (s) | HCl (C = 1) |glass

The importance of the electrodes stems from the fact that when it is placed in a solution of given acidity and the cell is completed by use of another electrode, the emf of the cell appears to depend primarily on the difference in the concentration or activity of the hydrogen ions on either side of the glass.

The glass membrane of the glass electrode separates two different solutions, as does the KCl salt bridge. Unlike the salt bridge, which provides for general ionic conduction across the liquid junction, the glass membrane most often used leads to a cell whose emf is primarily responsive to hydrogen ions. Glasses can be made that allow passage of only one type of ion, in this case the hydrogen ion, and thus the electrode can be constructed to be sensitive to this ion only.

Much of the importance of the glass electrode stems from its lack of response to various oxidizing and reducing agents and to a large variety of various ionic species. Difficulties may occur, however, if the glass electrode is used in solutions of high sodium ion concentration or in solution sufficiently alkaline to attack the glass membrane.

The glass electrode that responds to variations in the hydrogen activity is just one member of a growing list of practical electrode devices known as ion-selective membrane electrodes. The three general types of membranes used are illustrated in the fig. modifications of the glass membrane fo a glass electrode can make the membrane permeable and the electrode responsible t a glass electrode ions. Glass electrodes have been prepared that are sensitive to each of the ions of the alkali metal family and to the other ions such as NH4+, Ag+, and Cu+ as well as H+.

Solid state membranes can be represented by the fluoride ion electrode. The membrane material is the sparingly soluble crystalline substance LaF3. Fluoride ions are conducted through the crystals with ease while other ions are rejected. The fluoride ion electrode is highly specific and rugged, and thus is a valuable analytic tool.

When supplemented with a reference electrode, all such electrodes produce a potential that more or less conforms to the equation:

Ø˚ = const + RT/nF In aM

The net reaction, given the assumption that no junction reaction need be considered, is;

Right electrode; H+ (0.1) + e- ½ H2

Left electrode:                 ½ H2 ⇌ H+ (0.01) + e-

H+ (0.10M) ⇌ H+ (0.01M)

Since the value is zero, the cell emf can be written:

= - 0.05915 log a0.01 MH+/a0.10 MH+

Services:-
Ion Selective Electrodes Homework | Ion Selective Electrodes Homework Help | Ion Selective Electrodes Homework Help Services | Live Ion Selective Electrodes Homework Help | Ion Selective Electrodes Homework Tutors | Online Ion Selective Electrodes Homework Help | Ion Selective Electrodes Tutors | Online Ion Selective Electrodes Tutors | Ion Selective Electrodes Homework Services | Ion Selective Electrodes

Submit Your Query ???
Topics
Covalent Radii Crystal Shapes, Point Groups Diffraction Pattern Assignments Electron Diffraction Ionic Radii Lattice Energies Diffraction Lattices, Unit Cells Neutron Diffraction Waals Radii X-ray Diffraction Bond Moments Electric Capacitor Atoms, Molecules Properties Paramagnetism Electrolytic Dissociation Solution Ionic Strength Solvent Dielectric Effect Electrolysis Solutions Ionic Mobilities Electrolytes In Solutions Solutions Molar Conductance Solutions Specific Conductance Electrochemical Cell EMF Electrodes Ion Selective Electrodes Junction Potentials Cells Electromotive Force Standard Electrode Potentials Collision Theory Gas Viscosity Theory Elementary Reactions Lasers Molecule-Molecule Collisions Electrochemical Cell Photochemical Quenching Surface Decompositions Atomic Molecular Energies Molecular Energies Particle-in-a-box Particle-on-a-line Rotational Energies Schrodinger Wave Equation De Broglie Wave Length Vibrational Energies Waves And Particles Boltzmann Distribution Gas Heat Capacities Metals Heat Capacities Molecules Collection Energies One Dimensional Motion Partition Function Rotational Motions Thermal Energy Three Dimensional Motion Vibrational Motions Aqueous Ion Energies Bond Energies Chemical Systems Energy Enthalpy, Chemical Reactions Chemical System Enthalpy Thermodynamics First Law Heat Capacities Thermodynamics Molecular Thermal Energy Standard Enthalpy Substance Carnot Cycle Absolute Zero Entropies Entropy Thermodynamics Laws Entropy Molecular Basis Third Law Molecular Basis Rotational Energy Thermodynamics Second Law Thermodynamics Third Law Vapourization Entropy Vibrational Entropy Equilibria And Distributions Real Gases Equilibria Free Energy Equilibrium Constant Free Energy And Pressure Free Energy, Temperature Free Energy Function Free Energy Real Gases Free Energy Fugacity Non-ideal Gases Fugacity Thermodynamic Properties Chemical Equilibria Boyle Gas Pressure Continuity Of States Critical Point Gas Mixtures Kinetic Molecular Theory Gases-Properties, Theories Molecular Energies, Speed Molecular Interactions Real Gas PVT Temperature Volume Waals Gases Behaviour Waals Critical Point Molecular Diameters Virial Equation Diffusion Coefficient Diffusion Molecular View Donnan Membrane Equilibria Electrophoresis Macromolecular Dynamics Average Mass Range Solution Viscosity Sedimentation And Velocity Colloids Macromolecules Micelles Adsorption Isotherm Adsorption Of Gases Boiling Point Diagrams Pressure Temperature Relation Distillation Eutectic Formation Immiscible Liquids Phase Equilibria Liquid Surfaces Phase Rule Pressure Phase Diagrams Solid Compound Foundation Surface Tension Vapour Pressure Three Component System Vapour Pressure Composition Atomic States Bohr Atom Electron Spin Angular Momentum Hydrogen Hydrogen Atom Spectra Hydrogen Radical Factor Quantum Atomic Structure Quantum Mechanical Operators Variation Theorem Enzymes Catalyzed Reactions First Order Rate Equations Flash Photolysis Chemical Reactions Mechanism Enzyme Reactions Mechanism Reactions Mechanisms Photochemical Reactions Rate Equation Second Order Rate Equations Temperatures And Rates Unimolecular Gas Reactions Absorption Coefficient Einstein Coefficient Electromagnetic Induction Electronic Spectra Electron Spin Spectroscopy Infrared Adsorption Spectroscopy Microwave Absorption Nuclear Spin States Nuclear Magnetic Resonance Photoelectron Spectroscopy Polyatomic Vibrational Spectra Rotational Vibrational Spectra Conjugated Systems Spectra Transition Moment Character Tables Symmetry Group Theory Molecular Symmetry Types Orbital Symmetries Point Groups Reducible Representation Symmetry Elements, Operations Molecular Properties Symmetry Transformation Matrices Diatomic Molecule Orbitals Electronegativity Hybridization Hydrogen Molecule Ion Ionic Bond Molecular Orbitals Orbitals Pie Electrons Two Electron Bond Virial Theorem Partial Molal Properties Solute Free Energy Ideal Mixtures Solution Thermodynamic Property Liquid Vapour Free Energies Osmotic Pressure Partial Molal Quantities Solvent Free Energy Vapour Pressure Lowering