Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry4 Marks
Question
Explain electrochemical series or electromotive series.
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Answer
The conventions used in the construction of electrochemical series $($or electromotive series$)$ are as follows :
The $($reduction$)$ electrodes or half cells of the elements are written on the left hand side of the series and they are arranged in the decreasing order of their standard reduction potentials $( E^{\circ}$ red$).$
Reduction half reactions are written for each half cell in such a way that the species with higher oxidation state and electrons are on left hand side while reduced species with lower oxidation state are on right hand side.
The standard reduction potential of standard hydrogen electrode is $0.00 V$, i.e., $E _{ H ^{+} / H 2}^0=0.0 V$. The electrodes and half cell reactions with positive $E^0_{red}$ values are located above hydrogen and those with negative $E^0_{red}$ values below hydrogen. Above hydrogen, positive $E^0_{red}$ values increase, while below hydrogen negative $E^0$ values increase.
The positive $E^0_{red}$ values indicate the tendency for reduction and the negative $E^0_{red}$ values indicate the tendency for oxidation.
The elements, whose electrodes are at the top of the series having high positive values for $E^0 _{red}$ are good oxidising agents.
The elements, whose electrodes are at the bottom of the series having high negative values for $E^0 _{red}$ are good reducing agents.
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