Question

Although pure \(\mathrm{NaOH}\) and \(\mathrm{NH}_{3}\) have very different properties, their aqueous solutions possess many common properties. List some general properties of these solutions, and explain their common behavior in terms of the species present.

Short answer

Aqueous solutions of sodium hydroxide (NaOH) and ammonia (NH3) share properties due to their basic nature. Both solutions turn red litmus paper to blue, indicating an increase in pH, and react with acids to form a salt and water. NaOH dissociates into Na+ and OH- ions, while NH3 reacts with water to form NH4+ and OH- ions. Their common behavior stems from the presence of hydroxide ions (OH-) in both solutions, which are responsible for their basic properties and ability to neutralize acids. Thus, the presence of hydroxide ions is the key factor for their shared properties.

Step-by-step solution

Identifying the common properties

Both sodium hydroxide and ammonia are bases, so their aqueous solutions display the following common properties: 1. They turn red litmus paper to blue, indicating an increase in pH (basic) as they dissociate in water. 2. They will react with acids to form a salt and water, in a process known as a neutralization reaction.

Identifying the chemical species

In aqueous solutions, the chemical species present are as follows: 1. For sodium hydroxide, NaOH dissociates into Na+ and OH- ions: \[ NaOH(s) \rightarrow Na^+(aq) + OH^-(aq) \] 2. For ammonia, NH3 reacts with water molecules to form NH4+ and OH- ions in a reversible process: \[ NH_{3}(aq) + H_{2}O(l) \rightleftharpoons NH_{4}^+(aq) + OH^-(aq) \]

Explaining the common behavior

Both solutions have common behavior because of the presence of hydroxide ions (OH-) in the solution. The hydroxide ions are the active component responsible for the basic properties of the solution, such as increasing pH and neutralization reactions. In both cases, the hydroxide ions deposited in the solution react with hydrogen ions (H+) coming from an acid, turning them into water molecules. This is what makes it possible for bases like NaOH and NH3 to neutralize acids and form salts: 1. Sodium hydroxide solution with an acid: \[ NaOH(aq) + HX(aq) \rightarrow NaX(aq) + H_{2}O(l) \] 2. Ammonia solution with an acid: \[ NH_{3}(aq) + H_{2}O(l) + HX(aq) \rightarrow NH_{4}X(aq) + H_{2}O(l) \] Here, X represents the anion of the corresponding acid, forming NaX or NH4X as the resulting salt. Overall, the presence of hydroxide ions in both solutions is the critical factor that leads to their shared properties.