Question

In a \[0.250{\text{M}}\] solution of \[{\text{N}}{{\text{a}}_3}{\text{P}}{{\text{O}}_4}\] the concentration of the sodium ions would be:
A. \[0.250{\text{M}}\]
B. \[0.750{\text{M}}\]
C. \[0.0833{\text{M}}\]
D. \[1.99{\text{M}}\]

Answer 1

Hint:Stoichiometry can be used to predict concentration of entities if concentration of one entity is given in a balanced chemical equation. . Generally salts dissociate completely into its respective ions in aqueous solution.

Complete step by step answer:
Stoichiometry is for the determination of quantities of reactant and products involved in balanced chemical reaction.
For example: \[{{\text{H}}_2} + {\text{C}}{{\text{l}}_2} \to 2{\text{HCl}}\] , in this one mole of hydrogen reacts with one mole of chlorine to produce 2 mole of hydrochloric acid. Hence \[2{\text{g}}\] of hydrogen reacts with \[71{\text{g}}\] of chlorine to produce \[73{\text{g}}\] of hydrochloric acid. For a given balanced chemical equation, information of reactant or product can be determined if information of one of the species is given either in terms of moles, molecules, weight or atoms.
\[{\text{N}}{{\text{a}}_3}{\text{P}}{{\text{O}}_4}\] is known as trisodium phosphate. It is used to control the pH of water hardness precipitation and control agent in mildly acidic solution. \[{\text{N}}{{\text{a}}_3}{\text{P}}{{\text{O}}_4}\] is readily dissolved in water and produces sodium ions and phosphate ion.
The dissociation of trisodium phosphate in water will be as follow: \[{\text{N}}{{\text{a}}_3}{\text{P}}{{\text{O}}_4} \rightleftarrows 3{\text{N}}{{\text{a}}^ + } + {\text{PO}}_4^{ - 3}\] as we can see one mole of trisodium phosphate on dissociation produces 3 moles of sodium ions and one mole of phosphate ion. Now as given in question that \[0.250{\text{M}}\] solution of \[{\text{N}}{{\text{a}}_3}{\text{P}}{{\text{O}}_4}\] is taken. Thereby concentration of sodium ion produce will be: \[3 \times 0.250 = 0.75{\text{M}}\] and similarly we can say that concentration of phosphate ion produced will be: \[0.250{\text{M}}\] .

Thus, the correct option is B.

Note:
Generally concentration of a compound or a molecule represents in terms of molarity. Molarity is defined as the number of moles of a substance present in per Litre of a solution. On the other hand, concentration of gases is represented in terms of their partial pressure. Partial pressure of a gas is defined as pressure exerted by that gas in the mixture of gases.