Question

What is the molar solubility (s) of $B{a_3}{\left( {P{O_4}} \right)_2} \rightleftharpoons 3B{a^{ + 2}} + 2P{O_4}^{3 - }$ in terms of ${K_{sp}}$ ?

Answer 1

The molar solubility can be expressed in the terms of concentrations of ions of salt dissociated in presence of water. Salt is a molecule or chemical compound consisting of atoms generally atoms other than carbon and hydrogen which can dissociate easily into ions in presence of water.

Complete answer:
Given salt is barium phosphate. It consists of three barium atoms and two phosphorus atoms and eight oxygen atoms.
The given salt is the combination of the above atoms and dissociates into ions of barium and phosphate ions. Three barium ions and two phosphate ions were formed when the given salt is dissociated in the presence of water.
Barium is the element belonging to alkaline earth metals and has the valency of $2$ .
Thus, barium valency is two and the three barium ions carrying positive charge with each atom of valency $2$ are formed after dissociation.
The two phosphate ions can also be formed by carrying the negative charge and the valency of each phosphate ion will be $- 3$ .
The dissociation of barium phosphate can be as follows:
$B{a_3}{\left( {P{O_4}} \right)_2} \rightleftharpoons 3B{a^{ + 2}} + 2P{O_4}^{3 - }$
Let each ion produced be $s$
Then the molar solubility can be written as
$Ksp = {\left( {B{a^{ + 2}}} \right)^3}{\left( {P{O_4}^{3 - }} \right)^2} = {\left( {3s} \right)^3}{\left( {2s} \right)^2} = 108{s^5}$
Thus, the molar solubility is the product of concentrations of products.

Note:
The ions dissociated in the salt can be clearly written the charge and valency of atoms or groups must be known accurately. The charge on the positive ion i.e., cation and the negative ion i.e.…, anion must be balanced or should be equal.