An unknown salt is either KBr, NH4Cl, KCN, or K2CO3. If a 0.100 M solution of the salt is neutral, what is the identity of the salt?

Key Concepts

Acid-Base Neutrality

A neutral solution has a pH of around 7, indicating that the concentrations of hydrogen ions (H+) and hydroxide ions (OH-) are equal. In the context of salts, a neutral solution typically arises from the reaction of a strong acid with a strong base, resulting in no excess H+ or OH- ions. Understanding the acid-base properties of the ions in the salt is crucial for determining whether the solution will be neutral.

Salt Hydrolysis

Salt hydrolysis refers to the reaction of a salt with water, which can lead to the formation of acidic or basic solutions. When a salt dissolves, its constituent ions can interact with water, potentially altering the pH. For example, salts derived from strong acids and strong bases do not hydrolyze significantly, while those from weak acids or bases can create acidic or basic solutions, affecting neutrality.

Identifying Ions in Salts

To identify the unknown salt, it is essential to analyze the ions it contains. KBr consists of K+ and Br-, NH4Cl contains NH4+ and Cl-, KCN has K+ and CN-, and K2CO3 includes K+ and CO3^2-. By evaluating the properties of these ions, particularly their acid-base behavior, one can determine which salt would produce a neutral solution when dissolved in water.