How does concentration of the electrolyte changing over time affect the rate of electrolysis in sodium sulphate solution?

During the electrolysis of sodium sulphate solution, hydrogen is produced at the cathode and oxygen (from the hydroxide ion) is produced at the anode. Then I believe that the rate of electrolysis is directly proportional to current and current is proportional to the concentration of sodium sulphate solution.


So would I be right in saying that the rate of electrolysis would increase as time passes since the volume of water depletes; increasing the concentration of the solution over time?




The rate of electrolysis can be measured by the amount of gasses evolved, or by the current passing thru the cell.


As electrolysis proceeds and conditions change, the rate might very well change. After all, you are correct in implying that the conductivity of a more concentrated solution of sodium sulfate will be greater than the conductivity of a less concentrated solution.


Conductivity is one factor in determining the rate of electrolysis. Another factor is the applied voltage. If the voltage remains the same and the conductivity decreases, the current will increase, and the rate of gas production will increase as well.


However, if the cell is connected to a constant current power source, decreasing the conductivity will decrease the voltage measured across the cell, but the current (and therefore the rate of electrolysis) will remain constant.


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