Question

In the following cases, the number of solutions which have identical equilibrium molarity and analytical molarity are:
(a) 1 M glucose solution
(b) 1 M ${{H}_{3}}P{{O}_{4}}$solution
(c) Saturated AgI solution
(d) Solution of LiCl in ether

Answer 1

Hint: As we know that equilibrium molarity depicts the behavior of the solute when it is dissolvent in the solvent. Also, if a compound is acting like a nonelectrolyte in a solution, then its equilibrium molarity will be equal to its analytical molarity.

Complete answer:
Analytical molarity is the total number of moles of a solute, regardless of its chemical state whereas equilibrium molarity is the molar concentration of the species at equilibrium state.
-If a compound behaves as a non-electrolyte, it will dissolve in the solution without dissociation. Thus, its equilibrium molarity will remain the same as its analytical molarity.
-Let us check for all the compounds given in the question:-
(a) 1 M glucose solution: Since glucose does not act as an electrolyte thus it will not dissociate. This implies that analytical molarity of glucose will be equal to its equilibrium molarity.
(b) 1 M ${{H}_{3}}P{{O}_{4}}$ solution: It is a good electrolyte and will dissociate into ${{H}^{+}}$ and ${{H}_{2}}P{{O}_{4}}^{-}$ ions. Therefore its analytical molarity and equilibrium molarity will not be the same.
(c) Saturated AgI solution: AgI is insoluble in water and hence it will not dissociate. Therefore, its analytical molarity and equilibrium molarity will be the same.
(d) Solution of LiCl in ether: It does not behave as an electrolyte in ether and thus, it would not dissociate. This implies that analytical molarity of LiCl in ether will be equal to its equilibrium molarity.
-From the above data we conclude that (a), (b) and (c) will have identical equilibrium molarity and analytical molarity i.e., the number of solutions = 3.

Note:
While solving these questions, we must always know about the solubility of compounds in the given solvent to check whether its equilibrium molarity is identical to analytical molarity or not. Because solubility of the compound in the solvent will lead us to the conclusion that it is an electrolyte or a nonelectrolyte.