In the water treatment process, highly soluble sodium carbonate salt is added to precipitate out sparingly soluble calcium carbonate. Solubility effects Ī practical example used very widely in areas drawing drinking water from chalk or limestone aquifers is the addition of sodium carbonate to the raw water to reduce the hardness of the water. The solubility is therefore reduced to 1.40 x 10 −4 M, about five times smaller. However in a solution that is 0.0200 M in barium nitrate, Ba(NO 3) 2, the increase in the common ion barium leads to a decrease in iodate ion concentration. Its solubility in pure water is 7.32 x 10 −4 M. Solubility of barium iodate in presence of barium nitrate īarium iodate, Ba(IO 3) 2, has a solubility product K sp = 2 = 1.57 x 10 −9. As a result, the concentration of sulphide ions is decreased. The concentration of un-ionized H 2S is increased. Thus the ionization of H 2S is decreased. Due to the increase in concentration of H + ions, the equilibrium of dissociation of H 2S shifts to the left and keeps the value of K a constant. This makes H + a common ion and creates a common ion effect. To the above solution of H 2S, if we add hydrochloric acid, then it ionizes completely as There exists an equilibrium between un-ionized molecules and the ions in an aqueous medium as follows:īy applying the law of mass action, we have It is weakly ionized in its aqueous solution. Hydrogen sulphide (H 2S) is a weak electrolyte. 1.2 Solubility of barium iodate in presence of barium nitrateĮxamples of the common-ion effect Dissociation of hydrogen sulphide in presence of hydrochloric acid.1.1 Dissociation of hydrogen sulphide in presence of hydrochloric acid.Here, we know that the dissociated quantity of acetic acid x is very very less than 0.05, because the Kₐ value of a weak acid is very low. The initial concentration of the solution 0.1M(K a of CH 3COOH = 1.8 × 10 -5). In a solution of acetic acid if we add 0.1M sodium acetate, then calculate the new pH of the solution. It plays an important role in the regulation of buffer solutions.Used to completely precipitate the salt of an ion with very low solubility product for gravimetric estimation.Used in the precipitation of soaps in their manufacturing process.To reduce the sodium carbonate(Na 2CO 3) hardness of water using limestone and chalk.As this is different from the equilibrium established when a salt is dissolved, the common-ion effect does not apply to complex compounds formed by these transition elements. Transition elements usually violate this rule due to their ability to form complex compounds. When the salt AB is added to a solution in which CB is already dissolved, due to the common ion effect BC’s ionization reduces as a result its solubility also reduces and the equilibrium shifts towards the left.ĪB ⇌ A⁺ + B⁻ Limitations of Common Ion Effect Here, CB is a weak electrolyte compared to AB. In common-ion effect, when a different salt or electrolyte with one common ion, with the already dissolved salt or electrolyte, is added to the solution, the concentration of common ion increases due to which equilibrium of the dissolved salt or electrolyte shifts to the initial salt or electrolyte side causing its solubility to decrease.įor example, consider an imaginary salt AB and electrolyte CB. This is fundamentally based on Le Chatelier’s Principle, where if the concentration of any one of the reactants is increased then the equilibrium shifts in the direction in which these changes made to the equilibrium are nullified. Henry Louis Le Chatelier ( Source) Common Ion Effect ExplainedĬommon-Ion Effect is the phenomenon in which the solubility of a dissolved electrolyte reduces when another electrolyte, in which one ion is the same as that of the dissolved electrolyte, is added to the solution.
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