Chemical Engineering
Electrochemical Series.
Written by V R Saturday, 11 December 2010 19:09
A series which represents an arrangement of various metal electrodes in the increasing order of their standard reduction potentials or decreasing order of their standard oxidation potentials is called electrochemical series.
The metal which is placed above in the electrochemical series has a greater tendency to undergo oxidation so it will act as anode always when we connect with a metal below it,for the construction of a cell.
Factors affecting Over voltage.
Written by V R Saturday, 11 December 2010 19:05
- Nature and physical state of the electrode metal.
- Nature of the substance deposited.
- Current density.
- Temperature.
- PH of the electrolytic bath.
- Presence of inhibitors.
Over Voltage.
Written by V R Saturday, 11 December 2010 18:58
The difference between the potential of the electrode when gas evolution was actually observed and the theoretical reversible value of the same solution is called over voltage or over potential.
In the case of platinum electrode in dil H2SO4 for electrolysis the theoretical potential is 1.225V but the actual decomposition potential is 1.7V.The difference is called over voltage.
For continuous electrolysis applied emf should be greater than the back emf but in certain cases where evolution of gases occurs,it is observed that electrolysis does not occur until a potential higher than the theoretical potential is applied.
Advanatage and Disadvantage of Quinhydron electrode.
Written by V R Saturday, 11 December 2010 18:53
Advantages.
- It can be employed in many solutions in which hydrogen electrode is not applicable.
- It is very easy to set up and simple to operate.
- It is highly accurate in measurement.
- it has no external resistance and is free from salt errors.
Disadvantages
- It is not stable for a long time particularly above 30 degree celsuis.
- The solution must be free from oxidizing and reducing agents.
Advantage and Disadvantage of Glass electrode.
Written by V R Saturday, 11 December 2010 18:47
Advantages
- It can be used for the determination of PH of oxidizing agents,reducing agents viscous madia,in presence of proteins which interfere the other electrode etc.
- It can be used in the PH range of 0 to 12.
- It can be used in colored,turbid and colloidal solutions.
- It is simple to operate.
Disadvantages.
- Not used in ordinary potentiometer due to the high resistance of glass membrane.
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