Test: Solubility Equilibria of Sparingly Soluble Salts (26 July) - JEE MCQ

Common Ion effect is used in the purification of common salt, salting out of soap and qualitative analysis. In qualitative analysis, Ammonium Hydroxide is added in the presence of Ammonium Chloride to avoid the precipitation of V group radicals.

Common Ion effect is defined as the separation of the dissociation of a weak electrolyte by the addition of a strong electrolyte having some common ion. Therefore the degree of dissociation of Ammonium hydroxide decreases in the presence of Ammonium Chloride due to common Ion effect.

Solubility product Ksp is defined as the product of the concentrations of the ions of the salt in its standard solution at a given temperature raised to the power of the ions produced by the dissociation of 1 mole of the salt.

In the solution of two electrolytes, if the common ions’ concentration (Hydroxide Ion concentration in calcium hydroxide and barium hydroxide solution) is equal, then on mixing there is zero change in the degree of association in both of the electrolytes, such solutions are called isohydric solutions.

A salt is soluble if the solubility is greater than 0.1 M. A salt is slightly soluble if the solubility is between 0.01 M and 0.1 M and the salt is sparingly soluble if the solubility is less than 0.01 M.

The concept of solubility product helps in predicting the formation of the precipitate. In general, if the ionic product is greater than the solubility product, the precipitate is formed and if the ionic product is less than the solubility product, the precipitate is not formed.

For the salt AxBy, (AxBy = xAy+ + yBx+), the solubility of a sparingly soluble salt is given by xx.yy.sx+y. K_sp = xx.yy.sx+y, where x = 2 and y = 3; K_sp = 108S5 = 1 x 10^-25. S = 10^-5. The solubility of the salt is given by 10^-5.

The statement that is true regarding the solubility product (K_sp) of a sparingly soluble salt is that "K_sp is a constant value and is independent of temperature and pressure." K_sp is a constant at a given temperature and does not change with variations in pressure. It characterizes the equilibrium between the solid salt and its ions in a saturated solution at a specific temperature.

For the salt AxBy, (AxBy = xAy+ + yBx+), the solubility of a sparingly soluble salt is given by xx.yy.sx+y. K_sp = xx.yy.sx+y, where x = 1 and y = 3; K_sp = 27S4, by rearranging, we get solubility denoted by S as (Ksp/27)1/4.