Main Introduction Initial Observation and Hypothesis Materials and Equipment Experiment Discussion Applications Conclusions

INTRODUCTION

How do you determine the concentration of salt in a solution?

In everyday life people make and use salt solutions for different purposes. Our Mom is working at the Cheese Factory and she often has to make salt solutions of different concentrations (from 4% to 25%) for the cheese production. For example, when she makes Feta Cheese she has to put it in a 10% salt-water solution. Every time she makes salty water she has to be sure that the concentration is right. So we decided to help her and create a simple electrical device that could measure the concentration of the salt.

Knowing the fact that salty water is a conductor of electricity we decided to investigate the relation between the concentration of salt and the electrical current. Faraday’s Laws of Electrolysis give the relationship between the chemical and electrical properties of a solution.

Faraday’s Laws of Electrolysis

The Table Salt that our Mom uses at work is NaCl (sodium chloride). Its water solutions conduct an electric current, so NaCl is called electrolyte. When an electric current passes through the solution of sodium chloride chemical changes occur at the electrodes:

As a result chlorine gas is produced at the anode and the solution turns yellow. At the cathode the sodium hydroxide and hydrogen are produced. The solution fizzes as gasses are released.

This electrochemical reaction is called electrolysis.

Electrolysis was described by English scientist Michael Faraday and summarized in two laws:

First Law: The extent of an electrochemical reaction depends solely upon the quantity of electricity that is passed through a solution.

Second Law: The mass of a substance that is deposited as a metal, or evolved as a gas, by the passage of a given quantity of electricity is directly proportional to the molar mass of the substance divided by the number of electrons consumed or produced per formula unit.