Final answer:
A salt's solution may be acidic, basic, or neutral based on its constituent ions. NH4Cl, for example, forms an acidic solution due to the hydrolysis of the ammonium ion. Salts like K2CO3, derived from a strong base and a weak acid, typically form basic solutions.
Step-by-step explanation:
The nature of an aqueous solution of a salt, whether it is acidic, basic, or neutral, depends on the relative acid-base strengths of its constituent ions. To determine the nature of the solution, one must consider the cation and the anion that form the salt, and assess whether they are capable of undergoing acid or base ionization reactions with water (hydrolysis).
For example, ammonium chloride (NH4Cl) is composed of the ammonium ion (NH4+), which is the conjugate acid of the weak base ammonia (NH3), and the chloride ion (Cl-), which is the conjugate base of the strong acid HCl. Since HCl is a strong acid, its conjugate base Cl- has no tendency to react with water. However, because NH4+ comes from a weak base, it is capable of donating a proton to water, acting as an acid. This reaction is known as acid hydrolysis and results in an acidic solution.
To determine the nature of the solution for the following salts:
- (a) FeCl3: Iron(III) chloride will form an acidic solution because Fe3+ can undergo hydrolysis, releasing H+ ions into the solution.
- (b) K2CO3: Potassium carbonate is likely to form a basic solution because the carbonate ion can attract H+ from water, forming OH- and resulting in a basic solution.
- (c) NH4Br: Ammonium bromide will form an acidic solution similar to ammonium chloride for the same reasons.
- (d) KClO4: Potassium perchlorate will generally be neutral since the perchlorate ion is a weak conjugate base of a strong acid and K+ does not hydrolyze.
In contrast, salts formed from a strong base and a weak acid, like potassium carbonate (K2CO3), tend to form basic solutions because the anion (in this case, the carbonate ion) can remove a hydrogen ion from water, increasing the pH.