What is the electronic balance scheme?

The task is given: "According to the schemes, draw up electronic balance schemes". How can I do it? What is required for this? Let's try to figure it out together.

The essence of the method

First, let's look at what this method is. If the electronic balance scheme is correctly formed, it is possible to put in the proposed reaction all stereochemical coefficients.

The essence of this technique is to determine the degree of oxidation of individual elements that participated in the reaction. If in the left and right parts of the equation the element maintains a constant degree of oxidation, then the electronic balance scheme is compiled without it.

For elements that have changed their degree of oxidation during the interaction, the values obtained are taken into account in calculating the least common multiple.

How to make a balance

To begin with, you will have to put each element of its oxidation state, using certain rules. If a simple substance has entered into the interaction, it does not accept, nor does it give the other element electrons, hence its degree of oxidation is zero. Examples of compounds with a zero degree of oxidation are halogen molecules, metals.

In the binary compound of the second element, the degree of oxidation has a negative, and in the first - a positive value. In the sum (taking into account the number of atoms) should be zero. In calcium oxide, for example, in the first element the degree of oxidation is +2, and in the second (oxygen) -2. Their total value is zero, since the molecule is neutral.

If it is necessary to arrange the degree of oxidation in a more complex substance, then first the indices of the first and last elements are determined. Then, using mathematical calculations, determine the degree of oxidation of the central element. The sum of all indicators must be zero.

Algorithm of actions

How is the electronic balance scheme drawn up? In the left part of it, together with the degrees of oxidation, the elements that are involved in the oxidation-reduction process are recorded.

Further, the plus and minus signs indicate the number of electrons taken and delivered in the course of the chemical interaction. Between the number of electrons, the least common multiple is determined. Recall that a positive number is meant by it, which will be divided without a remainder into both figures relating to the electrons.

The electronic balance scheme is considered complete in the case when the coefficients are also defined in it. How to find them? The smallest common multiple must be divided into the electrons received and delivered in the process. The figures obtained will be the stereochemical coefficients.

It is also important to determine the reducing agent and oxidant, as well as the processes occurring during the interaction (oxidation and reduction). The obtained scheme of the electronic balance of the oxidation-reduction process will allow you to arrange the missing coefficients in the reaction.

OBD assignments in the final attestation

Based on this method, graduates are invited to complete a job from the "C" level. Success depends on the level of practical skills of the student, the degree of knowledge of the theoretical foundations.

For example, the task says: according to these schemes, draw up electronic balance schemes. In addition, some of the reactants, as well as some of the interaction products, can be missed. This question is considered to be a task of increased complexity, therefore it assumes a certain sequence of reasoning.

To begin with, all the elements in the known substances are determined by oxidation states, then substances that are missing in both parts of the reaction are recorded.

Then a balance is drawn up. According to the obtained scheme of the reaction, arrange the coefficients by the electronic balance method, as described above. The last action will be an indication of all the ongoing processes.

In the USE chemistry tests, a separate record of substances directly participating in the equation is proposed, followed by an indication of the oxidizing agent and reducing agent.

Conclusion

This method is by no means the only way to arrange the coefficients in the equation. It is also possible to use the half-reaction method, which allows you to equalize all substances recorded in the equation.