Concept Of Electrolyte And Non-Electrolyte Solution
Concept of Electrolyte and Non-electrolyte Solution
Many chemical reactions take place in a watery environment, such as reactions in the human body or reactions in plants and animals. Therefore, understanding the properties of the solution is very important. Keep in mind that the solution is a homogeneous mixture of two or more substances. Substantial amounts of substances are called solutes while many substances are called solvents. The solution can be in the form of gas (for example air), solid (eg brass), or liquid (eg sugar water). The discussion of electrolyte and non-electrolyte solutions in this chapter is a solution that dissolves solid, liquid or gas, with a solvent of water. [1]
At the beginning of the discovery of electricity, many people tried to study the effect of electric current on solids, liquids and gases. From experiments that have been carried out solids can be grouped into conductors (can conduct electric current, generally metal) and insulators (can not conduct electric current, generally non-metal). In addition to solids, liquids can also be grouped into liquids that can conduct electric current (electrolytes) and liquids that cannot conduct electric current (non-electrolytes). [2]
A device called an electrolyte test device (Figure 2.1) is used to test whether a liquid or solution can conduct electricity or not. The device is composed of a series of electrodes, which are made of two rods that can conduct electric current (made of graphite, copper, or platinum), which is connected with a direct power source (battery), and incandescent light bulbs. The two separate electrodes are then inserted in a container containing the liquid or solution to be tested. If the light bulb lights up, then the substance can conduct electricity (electrolytes). Conversely, if the liquid or solution cannot deliver electric current (non-electrolyte), the lamp does not turn on. [3]
Pure water is a very bad conductor of electricity. In testing with an electrolyte tester, there was no electric current flowing from one electrode to another electrode (the lamp was not lit). However, if the solid salt in the water is dissolved in the water, then the solution that occurs can deliver electrical current properly. This is indicated by turning on the lights on the electrolyte test equipment. The same event will also occur when dripping with concentrated solution of hydrochloric acid. NaCl solution in water and HCl solution in water can conduct electricity and is called an electrolyte solution, whereas liquid and solids dissolved in water are unable to conduct electricity, such as sugar. The solution is included in non-electrolyte solution. [5]
From the test results above, the question arises as to why liquid kitchen salt can conduct electricity while kitchen salt in the form of solids cannot conduct electricity? Why can't sugar, urea and alcohol solutions deliver electricity? [6]
Svante Arrhenius in 1884 proposed his theory, that in the electrolyte solution that acts to deliver electric current is the ions (electrically charged particles) that move freely in a liquid or solution. Solid NaCl is an ion compound in which there are Na + and Cl- ions. However, solid NaCl cannot conduct electric current because Na + and Cl-ions are very tightly bound in the Crystal so they are not free to move. This condition does not occur in liquid NaCl. In a liquid state, the distance between Na + and Cl-ions is very tenuous so that the ions are free to move to conduct electricity. [7]
This is the same thing with NaCl (solid NaCl dissolved in water). Because of the influence of water, kitchen salt (NaCl) will break down into Na + positive ions and Cl-free ions (anions) which are free to move. This process is called dissociation.
1. Ionic compound and covalent compound
Some substances in a solid state cannot conduct electric current but are in a liquid state and the solution can conduct electricity, for example kitchen salt (NaCl). Likewise with HCl which can conduct electricity after dissolving in water. [4]Pure water is a very bad conductor of electricity. In testing with an electrolyte tester, there was no electric current flowing from one electrode to another electrode (the lamp was not lit). However, if the solid salt in the water is dissolved in the water, then the solution that occurs can deliver electrical current properly. This is indicated by turning on the lights on the electrolyte test equipment. The same event will also occur when dripping with concentrated solution of hydrochloric acid. NaCl solution in water and HCl solution in water can conduct electricity and is called an electrolyte solution, whereas liquid and solids dissolved in water are unable to conduct electricity, such as sugar. The solution is included in non-electrolyte solution. [5]
From the test results above, the question arises as to why liquid kitchen salt can conduct electricity while kitchen salt in the form of solids cannot conduct electricity? Why can't sugar, urea and alcohol solutions deliver electricity? [6]
Svante Arrhenius in 1884 proposed his theory, that in the electrolyte solution that acts to deliver electric current is the ions (electrically charged particles) that move freely in a liquid or solution. Solid NaCl is an ion compound in which there are Na + and Cl- ions. However, solid NaCl cannot conduct electric current because Na + and Cl-ions are very tightly bound in the Crystal so they are not free to move. This condition does not occur in liquid NaCl. In a liquid state, the distance between Na + and Cl-ions is very tenuous so that the ions are free to move to conduct electricity. [7]
This is the same thing with NaCl (solid NaCl dissolved in water). Because of the influence of water, kitchen salt (NaCl) will break down into Na + positive ions and Cl-free ions (anions) which are free to move. This process is called dissociation.
What about HCl which is a covalent compound?
NaCl(s) + H2O (l)→ Na+(aq) + Cl-(aq)
Because HCl is a covalent compound, there is no ion in HCl, the presence is HCl molecules. These molecules even though they are free to move but cannot carry an electric charge because they are not ions. HCl is a polar covalent compound, which means it has positive and negative poles due to differences in electronegativity. In the water, the HCl molecule can decompose due to the influence of water which is also polar so that it forms H + and Cl- ions. The ions in this solution act as electrical conductors. The ionizing process is called ionization.
HCl(s) +H2O → H+(aq) + Cl-(aq)
Positive ions will move towards the negative electrode and negative ions will move towards the positive electrode by carrying an electric charge. The event of moving negative and negative ions to this electrode can be demonstrated by a simple experiment. Filter paper moistened with CuCrO4 solution is clamped with an alligator clamp connected to an electric current source. The positively charged pole will be yellow because the yellow CrO4-2 ions gather at the pole. While the negative pole will be blue because the blue Cu2 + ions gather at the pole. [8]
From the explanation above, it can be concluded that electrolyte solution can conduct electric current because it contains free-moving ions. These ions come from dissolved substances which break down into positive ions and free-moving negative ions carry an electric charge.
2. Strong Electrolyte Solution and Weak Electrolyte
In the test solution with an electrolyte tester, there are three possibilities that can be obtained, namely:
1. If the lamp lights up and gas bubbles arise, the solution has good conductivity and is called a strong electrolyte solution.
2. If the lamp is not lit or dim, and around the electrodes of gas bubbles arise, the solution tested has a weak conductivity or weak electrolyte solution.
3. If the lamp is not lit and there are no gas bubbles around the electrode, the solution being tested does not conduct electric current or non-electrolyte solution.
The conductivity of the electrolyte solution is determined by the many ions that occur by the ionization process. The more ions contained in a solution, the stronger the electrical conductivity.
All ion compounds that dissolve in water will become strong electrolyte solutions because they are completely dissociated. Some covalent compounds are classified as strong electrolytes because they are ionized in large percentages, while some other covalent compounds are only partially dissociated so that they are grouped into weak electrolyte solutions. The solution of covalent compounds which are not ionized is non-electrolyte. [9]
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