Written by V R Saturday, 11 December 2010 18:37
Glass electrode is an ion selective electrode,sensitive,sensitive to H+ ions,so it is used to measure H+ ion concentrations.It is used with other reference electrodes to generate a potential difference.
The principle of this electrode is when,a thin glass membrane is in contact with solutions of different H+ion concentrations on its two sides,a difference in potential is developed across the membrane.The magnitude of potential difference depends on the difference in H+ ion concentration and hence the PH can be calculated.
It is made up of a special glass of relatively low melting point and high electrical conductivity,in the form of a sealed glass tube filled with 0.1 M hcl a platinum wire is inserted into it,to make electrical contact.The glass electrode is represented as Pt;0.1M HCL glass test H+ solution.
The H+ ion concentration inside the electrode is constant.When this electrode is immersed into a solution of unknown H+,it becomes sensitive to the outside H+ concentration in the solution.Such a sensitivity arises because of the difference between the H+ ion concentration inside and outside.
Written by V R Saturday, 11 December 2010 17:03
The emf of a cell can not be measured directly by connecting with a voltmeter because during such measurements a part of the cell current is drawn by the voltmeter causing change in the emf due to the formation of reaction products at the electrodes and change in concentration of the electrolyte around the electrodes.So the measured emf is less than the actual emf.For precise emf measurements potentiometers are used which require small current at the balance point.
In potentiometric measurements of emf of a cell,an adjustable potential is applied and a cell is connected opposing the emf and the exact point of resistance in the potentiometer is found out with the help of a sliding contact.the resistance offered by the cell is the distance up to the null point detected by the null deflection of galvanometer.
Written by V R Saturday, 11 December 2010 16:56
The electrode potential is the tendency of a metallic electrode to loose or gain electrons when it is in contact with its own salt solution of unit concentration at 25 degree celsius.The tendency of an electrode in a half cell to loss electrons is oxidation potential and the tendency to gain electrons is known as reduction potential.For the same electrode oxidation and reduction potentials have the same value but the sign is different.
The value of electrode potential depends on the following factors:
- Nature of the metal.
- Concentration of the solution
- Temperature of the solution
Written by V R Saturday, 11 December 2010 16:50
Electro- chemistry is the branch of chemistry which deals with the relation between chemical energy and electrical energy.It gives the study of electrical properties of solutions of electrolytes.Electrical energy is carried through matter in the form of electric current.In order to have an electric current,the presence of a charge carrier as well as a force is essential.The force is usually provided by a battery or some other suitable source of electrical energy.The charge carriers are either electrons or ions.Ordinary substances are classified in to conductors,which allow the passage of electric current through it and insulators which will not allow the passage of electric current through it.
Written by V R Saturday, 11 December 2010 16:44
It is a device which converts chemical energy in to electrical energy and also referred as voltaic or galvanic cell.A cell is a single arrangement of two electrodes and an electrolytic solution capable of yielding electricity due to chemical action with in the cell or of producing chemical action due to passage of electricity through the cell.each cell is made of two electrodes and electrolyte.The electrode where oxidation occurs is called anode,while the electrode where the reduction occurs is called cathode.
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