# Electrochemistry: Application of Electrochemical Series and Primary Cell (For CBSE, ICSE, IAS, NET, NRA 2022)

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## Application of Electrochemical Series

### It Helps to Predict a Redox Reaction

A given ion will oxidize all the metals below it and a given metal will reduce ions of any metal placed above it in the series.

### It Helps to Calculate the Emf of a Galvanic Cell

cell should always be positive. If cell comes as it means the cell cannot work and electrodes should be interchanged.

### It Helps to Predict the Feasibility of a Redox Reaction

The positive cell indicates the redox reaction is possible.

### It Helps to Predict Whether a Metal Can Liberate Hydrogen from Acids

Any metal which is above hydrogen in the electro chemical series can liberate hydrogen from acid since it is a better reducing agent than hydrogen.

## Nernst Equation for Electrode Potential

• Nernst equation relates electrode potential to the concentration of ions in the electrolyte.
• An electrode reaction is always written as reduction reaction. Let us take a general example for a metal

The Nernst equation for its electrode potentials is:

Electrode potential

Standard electrode Potential (Reduction)

gas constant in

Temperature in Kelvin

no of moles involve in the electrode reaction

molar concentration of ion

concentration of pure solid metal taken as unity

Thus,

By putting the value of R, T and F in equation

, ,

## Nernst Equation for Cell

For a general cell reaction:

## Primary Cell

A primary cell is the one that is consumed chemically when current is drawn from it.

## Secondary Cell

A secondary cell is the one which after discharge can be recharged by passing electricity through it and carrying out electrolysis.

## Dry Cell

• It consists of a zinc container which also acts as the anode and a carbon (graphite) rod which acts as the cathode.
• Around carbon rod, a moist paste of graphite, ammonium chloride and manganese dioxide is placed which acts as the electrolyte (Fig) .