Process of Electrolysis

The interactive system we present next illustrates the electrolysis process, specifically the electrolysis of water. Web-based lessons can be designed as simple HTML pages that include images and text. We augmented the pages with a 3D interactive simulation of the electrolysis process.

The electrolysis of water is the process of decomposition of molecules of water into ions of hydrogen and oxygen. To simulate the electrolysis of water we design in X3D a semitransparent cylinder and two electrodes of different signs that are connected to a source of electricity. We represent molecules of water as small spheres interconnected. When the circuit is closed we start the animation process by representing electrons moving from the positive pole to the negative one. In the process, molecules of water split into negative ions of hydroxide (HO-) and positive ions of hydrogen (H+). The hydroxide ions represented as red spheres combine with three other hydroxide ions to form one molecule of oxygen and two molecules of water while releasing four electrons. Meanwhile the yellow spheres of hydrogen follow the path to cathode where they will accept an electron to become atoms of hydrogen.

The transfer of the electrons between the electrodes and the ions is emphasized by the red arrows that show the direction of ions formation. The positive hydrogen ions will continue the movement into the water until they meet other ions of the same type and become gaseous molecules of hydrogen.

Electrolytes and Non-Electrolytes

Solutions and melting electrolytes conduct electricity. The substances that conduct electricity are called conductors. Substances that can conduct electricity are for example: HCL, NaOH, NaNO3 and they are called electrolytes. The substances that don't conduct electricity (for example distilled water, sugar, glycerin) are called non-electrolytes. Chemical reactions are involved when the electricity is conducted through melting electrolytes or solutions of electrolytes chemical reactions happen.

Electrodes are represented by metallic plates that are inserted in solution or in melting, and then connected to one pole of the continuous electric current source.

The electrode connected to the positive pole (+) of source of electric current is called anode, and the electrode connected to the negative pole (-) is called cathode.

Experiments

Experiment 1. Two electrodes are inserted in a pot with distillate water. The electrodes are connected to the poles of a continuous electric current source. In this circuit is integrated an electrical bulb. Can be observed that the bulb is not lighting.
Electrolysis of sodium chloride
Electrolysis of water

 

Two electrodes are inserted in a pot with solution of NaCl. The electrodes are connected to the poles of a continuous electric current source. In this circuit is integrated an electrical bulb. Can be observed that the bulb is lighting.

Explanation.

The solution of NaCl contains positive ions of Na+ and negative ions of Cl-:

The ions have a disordered movement, as long as the solution is not under the action of electrical field. The electrodes connected to a source of electric current apply forces of attraction over the ions with opposite sign. The disordered movement of ions is transformed in a oriented movement. The negative ions of chlorine, called cations, are going to the positive pole, where they give up one electron and they transform into atoms of chlorine. The atoms of chlorine bound in pares forming molecules of chlorine (Cl2), which being gas bubble to the surface.

Meanwhile, the positives ions of sodium, called anions, follow the path to the cathode where they accept an electron and transform in atoms of sodium, which being a solid are deposited to the cathode.

Remember!

The substances that to electric current to be passed into melting and solution, (for example HCl, NaOH, NaNO3) are called electrolytes. The substances that don’t conduc electricity (for example sugar, glycerin) are called non-electrolytes.