Question

Is \(\mathrm{Ba}_{3}\left(\mathrm{PO}_{4}\right)_{2}\) a basic salt? Justify your answer. $$ \mathrm{Ba}_{3}\left(\mathrm{PO}_{4}\right)_{2}(s) \rightleftharpoons 3 \mathrm{Ba}^{2+}(a q)+2 \mathrm{PO}_{4}^{3-}(a q) $$

Short answer

\(\mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2}\) is a basic salt because it is made from a strong base (barium hydroxide) and a weak acid (phosphoric acid).

Step-by-step solution

Understand Salt Formation

Salts are formed by the reaction of an acid and a base. If the base is stronger than the acid in terms of their capacities to donate hydroxide ions (OH-) or accept protons (H+), respectively, the resulting salt will be basic in nature.

Identify the Components of the Salt

In the given chemical equation, barium phosphate, \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \), dissociates into barium ions (\( \mathrm{Ba}^{2+} \) ) and phosphate ions (\( \mathrm{PO}_{4}^{3-} \) ). Barium comes from barium hydroxide (a strong base), and phosphate comes from phosphoric acid (a weak acid).

Determine the Nature of the Salt

Since barium hydroxide is a strong base (completely dissociates in water) and phosphoric acid is a weak acid (does not completely dissociate in water), the resulting salt, \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \), favors the formation of OH- ions over the acceptance of H+ ions. Therefore, the salt is basic in nature.

Key concepts

Salt Formation

Salt formation is a fundamental concept in chemistry involving the reaction of an acid with a base to create a salt and water, typically observed in neutralization reactions.

In the context of the exercise, \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \) is a compound that results from the reaction between barium hydroxide (a strong base) and phosphoric acid (a weak acid). When an acid reacts with a base, the hydrogen ions (H+) from the acid and the hydroxide ions (OH-) from the base combine to form water (H2O), whereas the remaining ions form the salt.

It's important to recognize that the strength of the base and acid involved will determine the resulting salt's nature. If the resulting salt comes from a strong base and a weak primary acid, as in the case of barium phosphate, the salt often has basic properties. This is because the salt can react with water in a process known as hydrolysis, producing hydroxide ions that raise the solution's pH.

Dissociation of Salts

Dissociation of salts into their constituent ions in water is a key concept in understanding the behavior of salts in solution.

When \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \) is placed in water, it dissociates into barium ions \( \mathrm{Ba}^{2+} \) and phosphate ions \( \mathrm{PO}_{4}^{3-} \). This process is crucial because it allows us to analyze the resulting solution's properties. For instance, the presence of \( \mathrm{Ba}^{2+} \) ions in water suggests the possibility of hydrolysis occurring, where the cation might react with water and produce hydroxide ions, contributing to a basic solution.

Because \( \mathrm{PO}_{4}^{3-} \) ions come from a weak acid, they do not tend to recombine with hydroxide ions to reform the acid. Consequently, free hydroxide ions may remain in the solution, further confirming the basic nature of the salt.

Acid-Base Reactions

Acid-base reactions are transformative processes where an acid and a base react to form water and a salt. These reactions are foundational for understanding the properties of many substances in chemistry, including salts such as \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \).

The nature of the resulting salt is intimately connected to the strengths of the original acid and base. If a strong base and a weak acid react, the resulting solution tends to be basic because the salt can increase the pH by yielding hydroxide ions upon dissociation. Conversely, if a strong acid and a weak base react, the resulting salt often makes the solution acidic.

Analyzing the equation from the exercise, \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \) is formed when barium hydroxide, a strong base, reacts with phosphoric acid, a weak acid. This favors the formation of a salt that, when dissolved, slightly increases the concentration of hydroxide ions in the solution, leading to a basic pH. Hence, we can conclude that \( \mathrm{Ba}_{3}(\mathrm{PO}_{4})_{2} \) is a basic salt as it originates from the interaction between a strong base and a weak acid.