Solubility of salts and their electrical conductivity
When studying the chemical properties of compounds, their ability to dissolve in water is a fundamental aspect. According to the generally accepted classification, all salts are strictly divided into two main groups: soluble and practically insoluble. To quickly determine whether a particular substance belongs to one of these groups, special reference data are used. As a rule, they are systematized and presented in the form of a solubility chart, which can often be found on the inside cover of textbooks.
The most important general property uniting salt solutions is their high electrical conductivity. However, the intensity of current conduction is not absolutely identical for all classes of chemical compounds. If we carry out a comparative characterization of the conductivity of various solutions under strictly identical conditions, a clear pattern can be revealed. Solutions of strong acids and bases rank first in electrical conductivity—their indicators are consistently higher than those of salt solutions. In turn, salt solutions demonstrate significantly higher electrical conductivity compared to solutions of weak acids and bases.
Experimental confirmation of electrical conductivity
Theoretical propositions about the ability of solutions to conduct electric current are clearly confirmed during laboratory tests. An experiment demonstrating the dependence of conductivity on solution composition is illustrative.
The methodology of this experiment is quite simple: an electric circuit is assembled, integrating an ordinary electric lamp. A glass beaker filled with a solution of sodium chloride (Natrii chloridum) is included in this circuit as a key element. While observing the setup, an important phenomenon is recorded: the brightness of the electric lamp is not a constant value; it directly depends on the amount of salt that has been dissolved in water.
The main conclusion that this experiment allows us to make is as follows: a targeted increase in the concentration of salt ions in a liquid naturally increases the overall electrical conductivity of the test solution.
Algorithm for compiling ionic equations
The solubility chart serves not only as a reference for physical properties, but also as the main tool for writing chemical reactions. To correctly compile ionic equations, it is required to strictly follow an algorithm consisting of four basic rules.
- Recording form of substances. This rule regulates how exactly a substance should be presented in the equation. It is permitted to record exclusively strong electrolytes in the ionic form, provided that they are directly in solution. Conversely, it is necessary to record non-electrolytes and weak electrolytes in the molecular form. In addition, even strong electrolytes are recorded as whole molecules if in a given reaction they exist in a crystalline (solid) or gaseous state.
- Reduction procedure. To transition from the full ionic equation to its reduced form, it is necessary to analyze the left and right sides of the record. Identical ions are completely excluded from both sides of the equation. From a chemical perspective, this means removing those particles that actually took no part in the ongoing chemical process.
- Electrical charge balance. Any correctly compiled ionic equation obeys the law of conservation of charge. This means that the total electrical charge of all particles located on the left side of the equation must be absolutely equal to the total charge of the particles on the right side.
- Use of reference data. When writing reaction equations, it is unacceptable to rely solely on intuition. It is necessary to constantly be guided by two main sources: a detailed list of strong and weak electrolytes, and the solubility chart of salts, acids, and bases.
Class and exam questions
How does salt concentration affect the electrical conductivity of a solution?
The higher the concentration of ions of the dissolved salt, the higher the electrical conductivity of the solution. This is clearly confirmed by an increase in the brightness of the lamp glow in the electric circuit.
Which substances must be recorded in molecular form in ionic equations?
Non-electrolytes, weak electrolytes, and strong electrolytes (if they are in a solid (crystalline) or gaseous state) are recorded as molecules.
What conducts current better: a salt solution or a weak acid solution?
Under equal conditions, a salt solution has a higher electrical conductivity than solutions of weak acids and bases. However, they are inferior to solutions of strong acids.
Why is it necessary to cancel out ions when writing equations?
Canceling out identical ions in the left and right parts makes it possible to exclude from the record those particles that actually took no part in the chemical process.
What else to study on this topic
- Classification of strong and weak electrolytes
- Comparative characterization of the conductivity of acids and bases
- Features of recording gases and crystalline substances in reactions
- Practical application of reduced ionic equations
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