Electrolysis of Sodium Chloride - NaCl.

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George Karsa

Mr Van Mallearts

Chemistry Coursework

Electrolysis of Sodium Chloride – NaCl



I aim to find out how the concentration of Sodium Chloride (NaCl) affects the current.


Electrolysis is the decomposition of a substance or compound with the use of electricity.

Electricity is the free-flow of electrons (or charged particles).

An electrical current is only able to pass through a substance if the electrons (or charged particles) are able to move.

Graphite’s electrons are free to move, hence it is a conductor of electricity. Ions enable charges to move freely in solutions, and therefore also are conductors. There are two graphite electrodes; the negative electrode – the cathode, and the positive electrode – the anode.

In this experiment the ions present are;

NaCl = Na+, Clˉ

H2O  = OHˉ and H+.


At the cathode;

                        Na+, H+

The most reactive out of these remains in the solution ;

2 H+ +2eˉ= H2 (g)

Here, we experience a gain of electrons, called a reduction 

At the anode;

                        Clˉ, OHˉ

If a halogen is present, halogen gas given off - Cl2

Here, we experience a loss of electrons, called an oxidation

Left in the solution;

                        Na+, OHˉ


I predict that as the concentration of Sodium Chloride (NaCl) is increased, the current will increase also. I think this because the current and concentration are proportional; electricity is the free-flow of electrons (or charged particles) and therefore if there are an increased amount of electrons or charged particles by increasing the concentration of NaCl, then there will also be an increase in the current.

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  1. Concentration of Sodium Chloride (NaCl) dependant variable
  2. Distance between electrodes
  3. Surface area of electrodes
  4. Current independent variable


  • Sodium Chloride (NaCl)
  • Beaker
  • Measuring cylinder
  • Weighing boat
  • Weighing scales
  • Electrode x2
  • Spatula
  • Connecting wires
  • Battery pack
  • Ammeter

Safety Precautions

  1. I must ensure the power supply is turned off whilst connecting the wires to the ammeter and battery pack as electricity is highly dangerous.
  2. I must ensure I wear safety goggles during the experiment because the solution could become vigorous and begin to ‘spit’, so I would need ...

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