FACTORS AFFECTING REACTIONS IN CELLS

The effect of current strength on the chemical reaction in an electrolytic cell. Faraday’s Law The amount of substance that undergoes oxidation or reduction at each electrode is directly proportional to the amount of electricity that passes through the cell.

The Cell Potential When a sensitive voltmeter is connected in the circuit of an electrochemical cell, the reading on the meter is the cell potential or the emf of the cell. The cell potential is the maximum potential difference that the cell can deliver when all the chemical potential energy is converted into electrical energy.

The standard emf (Eocell) is the emf when the cell operates under standard conditions: Solute concentration = 1 mol.dm-3 Gas pressure = 1 atmosphere or 101,3kPa Temperature = 298K

Factors that affect the cell potential: Nature of the substances – each different combination of elements in a cell will give a different emf. The nature of the substances is the only determinant of emf. Concentration of reagents – these factors have very little effect on the emf of a cell. The concentration of the reagents affects Vcell, the actual potential delivered by the cell.

Vcell decreases with time when the cell is operating. Vcell decreases when the concentration of the reactant ions in the electrolyte decreases.