Electrolysis is a process characterized by redox properties with respect to the constituent elements of salts and other compounds in melts or solutions when an electric current passes through them.
By means of electrolysis, it is possible to obtain metals and non-metals, characterized by a high degree of their chemical purity. This reaction is simple and affordable, it can even be modeled at home. This will require a certain source of constant electric current, a pair of electrodes and a pre-prepared electrolyte. The most basic property of electrolytes is their ability to conduct electric current.
There are electrolysis of solutions and molten salts, with a general similarity, they have a number of significant differences. Carrying out the electrolysis of solutions, one should take into account the participation of solvent ions in the process. The electrolysis of melts is characterized by the presence of only ions of the substance itself.
To obtain the desired product (be it metal, gas or some non-metal), you should worry about choosing a suitable electrode and preparing an appropriate electrolyte.
The material for the electrodes can be any conductor of electric current. In most cases, metals and alloys are used; among non-metals, graphite rods (carbon) can show good performance as an electrode. Very rarely, but technological solutions are known in which liquids serve as the material for the electrodes.
Everything is ready to carry out the electrolysis of salt solutions. The positive electrode is called the anode. For the negative electrode, the designation is the cathode. Carrying out the electrolysis of solutions, the anode is oxidized (dissolved), and the cathode is restored. It is very important that the “dissolution” of the anode does not affect the chemical process that takes place in the solution (melt). Otherwise, the main condition for the anode is its inertness. Ideally, it can be made from platinum, but graphite (carbon) anodes are also very effective.
Almost any metal plate is suitable for the cathode (it will not dissolve). Copper, brass, carbon (graphite), zinc, iron, aluminum cathodes are widely used in modern industry.
Carrying out electrolysis of solutions at home, practically from improvised materials it is possible to obtain substances such as oxygen, chlorine, hydrogen, copper, weak acid or alkali, sulfur. Do not abuse the experiments with chlorine - it is poisonous!
To obtain oxygen and hydrogen, it is necessary to electrolyze a solution of baking soda (an alternative is soda ash). Near the electrode "+" (anode) oxygen will be released in the form of bubbles, at the cathode ("-") - hydrogen. To the question of why the reduction of hydrogen and not sodium occurred, as one might suppose, one can find the answer: Na is to the left of H2 in the series of metal stresses, respectively, in the competition of two cations, hydrogen won over sodium. Using the example of this reaction, we witnessed how the electrolysis of solutions, in fact, turned into the electrolysis of a solvent (water).
Using the solution of copper sulfate as the electrolyte , we get a dark red coating on the cathode, which is a pure metal that has been reduced by copper.
According to the results of two experiments on electrolysis, some generalizations can be made. The positive anode becomes a place for the restoration of anions; in both of the above cases, it turned out to be oxygen. Cations are reduced at the cathode, in our experiments they turned out to be hydrogen - in the first case, copper - in the second. As a rule, metals or hydrogen are cations, but in some cases they can be both non-metals and gases. The oxidation state of an element plays an important role in the recovery process.