Problem 62 - A Complete Resource Book in Chemistry for JEE Main

Question

With \(\mathrm{NH}_{4} \mathrm{OH}\), the silver nitrate is decomposed to give a brown precipitate of (a) \(\mathrm{Ag}_{2} \mathrm{O}\) (b) \(\mathrm{AgO}\) (c) \(\mathrm{Ag}(\mathrm{OH})_{2}\) (d) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\)

Step-by-Step Solution

Answer

The correct answer is (a) \(\mathrm{Ag}_{2} \mathrm{O}\).

Step 1: Write the reaction equation

Ammonium hydroxide \(\mathrm{NH}_{4} \mathrm{OH}\) reacts with silver nitrate \(\mathrm{AgNO}_{3}\). The typical reaction can be written as: \[\mathrm{AgNO}_{3} + \mathrm{NH}_{4} \mathrm{OH} \rightarrow \mathrm{Ag}_{2} \mathrm{O} + \mathrm{NH}_{4} \mathrm{NO}_{3} + \mathrm{H}_{2} \mathrm{O}\].

Step 2: Identify the precipitate

In the above reaction, silver oxide \(\mathrm{Ag}_{2} \mathrm{O}\) forms as a brown precipitate. This is the key aspect of the reaction.

Step 3: Analyze the options

Compare the given options with the chemical products in the reaction. The options provided are: (a) \(\mathrm{Ag}_{2} \mathrm{O}\), (b) \(\mathrm{AgO}\), (c) \(\mathrm{Ag(OH)}_{2}\), (d) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\).

Step 4: Correct answer selection

Since the brown precipitate from the decomposition of silver nitrate using ammonium hydroxide is \(\mathrm{Ag}_{2} \mathrm{O}\), the correct option is (a).

Key Concepts

Precipitation Reactions

Precipitation reactions occur when two soluble salts in aqueous solution react to form one or more insoluble products, known as precipitates. These reactions are a type of double displacement reaction where ions swap partners to create a new compound that is insoluble in water. When the new compound is formed, it becomes visible as particles or as a solid that settles out of the solution.

When writing equations for precipitation reactions, the anions and cations that participate are typically represented as dissociated ions in the initial solution. Upon mixing, the ions can recombine to form a compound that precipitates. For example, when a solution of silver nitrate (AgNO₃) is mixed with ammonium hydroxide (NH₄OH), a brown precipitate of silver oxide (Ag₂O) forms, indicating a precipitation reaction has occurred. This visible change helps in identifying the formation of specific products in chemical reactions.

Silver Nitrate Reactions

Silver nitrate is a versatile compound that participates in various chemical reactions. It is ionic, composed of the silver cation (Ag⁺) and the nitrate anion (NO₃⁻). When dissolved in water, silver ions are free to react with other ions or molecules present in the solution.

One notable reaction is with ammonium hydroxide to produce silver oxide. Here, AgNO₃ is mixed with NH₄OH, leading to the formation of a brown precipitate of Ag₂O, demonstrating how silver can readily react with bases to form more complex compounds. This reaction is also an example of a chemical decomposition, showcasing the breakdown of AgNO₃ into new products through reactive interactions.

Ammonium Hydroxide Chemistry

Ammonium hydroxide, often represented chemically as NH₄OH, is a solution of ammonia in water. In chemical reactions, it acts as a weak base, offering a source of hydroxide ions (OH⁻) for reactions. Its weak nature means it does not fully dissociate in water but can still participate in various chemical transformations.

When ammonium hydroxide is combined with silver nitrate, a chemical reaction occurs where the ammonia assists in forming silver oxide, showcasing the basic properties of NH₄OH. This reaction highlights its role in precipitating reactions, especially with transition metals like silver. Knowing the behavior of NH₄OH is crucial in understanding reactions that are important in chemistry for synthesizing different compounds and demonstrating practical applications such as solution reactions and neutralizations.