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When a common ion (an ion already present in the solution) is added to a solution, the common ion effect defines the effect on equilibrium that happens. A solute’s solubility is reduced by the common ion effect. It can also change the pH of buffering solutions by introducing additional conjugate ions.
The equilibrium response of ionic association/dissociation is governed by Le Chatelier’s principle, which explains this behaviour. The effect is most typically recognised as a decrease in the solubility of salts and other weak electrolytes. Increasing the concentration of one of the salt’s ions decreases the concentration of both ions until the solubility equilibrium is attained. The effect is due to the fact that the original salt and the additional chemical share one ion.
Examples of Common Ion Effects
When sodium chloride (NaCl) is introduced to an HCl and water solution, the common ion effect is demonstrated. After the hydrochloric acid and water have reached equilibrium, the products are
Na+ and Cl– are formed when the NaCl dissolves in the solution. The concentration of Cl– ions rises as the sodium chloride dissolves. The system compensates by recombining the Na+ and Cl– to form NaCl, a solid that precipitates out of solution. In effect, more Cl– ions were added to the solution in equilibrium, which pushed the equilibrium back to the left.
Factors Involved in Common Ion Effect
The effect is most typically recognised as a decrease in the solubility of salts and other weak electrolytes. Increasing the concentration of one of the salt’s ions reduces the concentration of both ions until the solubility equilibrium is attained. The effect is due to the fact that the original salt or the additional chemical share one ion.
Solubility Effects
The addition of sodium carbonate to the raw water to lessen the hardness of the water is a practical example extensively employed in locations receiving drinking water from chalk or limestone aquifers. To precipitate out sparingly soluble calcium carbonate, highly soluble sodium carbonate salt is used in the water treatment process. The calcium carbonate precipitate, which is very pure and finely split, is a valuable by-product that is utilised in the production of toothpaste.
Buffering Effect
Acid and its conjugate base, or a base and its conjugate acid, are present in a buffer solution. [2] When the conjugate ion is added to the buffer solution, the pH of the solution changes. If sodium acetate and acetic acid are dissolved in the same solution, they will both dissociate and ionise, resulting in acetate ions. Because sodium acetate is such a strong electrolyte, it totally dissociates in water. Because acetic acid is a weak acid, it only mildly ionises. The addition of acetate ions from sodium acetate suppresses acetic acid ionisation and shifts the equilibrium to the left, according to Le Chatelier’s principle. As a result, the acetic acid’s % dissociation decreases and the pH rises. The existence of a conjugate base or acid limits an acid or a base’s ability to ionise.
This will also decrease the hydronium concentration, and thus the common-ion solution will be less acidic than the solution containing only acetic acid.
Importance of Common Ion Effect
In chemistry and other studies involving chemical equilibrium, the influence of common-ions in equilibrium solutions is indeed an important and fascinating element. When a salt is dissolved in a solution that contains another supply of one of its ions, the common-ion effect occurs. It is a common occurrence in chemical analysis and also has a substantial impact on salt solubility and dissolution rate. It’s also known as a phenomenon in which a small amount of powerful electrolyte containing a common-ion can suppress the degree of dissociation like any weak electrolyte.
Conclusion
The solubility equilibrium alters in the way indicated by Le Chatelier’s principle when a common cation or common anion is added to a solution of a sparingly soluble salt. When a common ion is present, the salt’s solubility is almost always diminished.
- The common ion impact is most obvious in the reduction of solid solubility in solutions. Because of a shift in equilibrium, a compound’s solubility normally drops when common ions are added.
- In the modulation of buffers, the common ion impact is also important. An acid or base, as well as its conjugate counterpart, are present in buffering solutions. The pH of the solution will eventually change as additional similar conjugate ions are added.
- When calculating solution equilibrium following the addition of ions already present in the solution, the common ion effect must be taken into account.
The solubility of solutes in a reacting system is affected by the common-ion effect, which is a change in chemical equilibrium. The phenomenon is a regular occurrence in chemistry analysis and industrial research due to the application of Le-principle Chatelier’s for equilibrium reactions. It’s a significant phenomena that may be applied in practice to better understand particular reaction settings that favour greater product production
