Problem 64 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is formed when silver nitrate is treated with caustic soda? (a) \(\mathrm{Ag}_{3} \mathrm{~N}\) (b) \(\mathrm{Ag}\) (c) \(\mathrm{AgNO}_{2}\) (d) \(\mathrm{Ag}_{2} \mathrm{O}\)

Step-by-Step Solution

Answer

Silver oxide (\(\mathrm{Ag}_2\mathrm{O}\)) is formed.

Step 1: Identify the Reactants

In this problem, the reactants are silver nitrate (\(\mathrm{AgNO}_3\)) and caustic soda (sodium hydroxide, \(\mathrm{NaOH}\)). We need to figure out the product of their reaction.

Step 2: Determine Reaction Type

Silver nitrate and caustic soda typically undergo a double displacement reaction. This means the cations and anions of the reactants will swap partners.

Step 3: Swap the Ions

In a double displacement reaction, silver ion (\(\mathrm{Ag}^+\)) from silver nitrate will combine with the hydroxide ion (\(\mathrm{OH}^-\)) from caustic soda to form silver hydroxide \((\mathrm{AgOH})\). Sodium ion \((\mathrm{Na}^+)\) and nitrate ion \((\mathrm{NO}_3^-\)) will form sodium nitrate \((\mathrm{NaNO}_3)\).

Step 4: Consider Product Stability

Silver hydroxide \((\mathrm{AgOH})\) is not stable and decomposes to form silver oxide \((\mathrm{Ag}_2\mathrm{O})\) and water. Thus, silver oxide is the solid product formed.

Step 5: Write the Balanced Equation

The balanced chemical equation for the reaction is: 2\(\mathrm{AgNO}_3\) + 2\(\mathrm{NaOH}\) → \(\mathrm{Ag}_2\mathrm{O}\) + 2\(\mathrm{NaNO}_3\) + \(\mathrm{H}_2\mathrm{O}\). Silver oxide \((\mathrm{Ag}_2\mathrm{O})\) is the compound formed.

Key Concepts

Silver nitrate

Silver nitrate, represented by the chemical formula \(\mathrm{AgNO}_3\), is an important compound in chemistry. It appears as a white crystalline solid and is highly water-soluble. Silver nitrate is known for its ability to act as a source of silver ions, making it a key reagent in various chemical reactions. This compound is used in a variety of fields from photography to medicine.

In chemical reactions, silver nitrate is known to react with numerous substances to form new products. Its main role is to provide silver ions \((\mathrm{Ag}^+)\) which can participate in further reactions. This makes silver nitrate very handy in studying and conducting displacement reactions in the laboratory.

Double displacement reaction

A double displacement reaction, also known as a metathesis reaction, is a type of chemical reaction where two compounds exchange ions or elements to form two new compounds. In the context of silver nitrate reacting with caustic soda \((\mathrm{NaOH})\), the ions exchange places:

• Silver ions \((\mathrm{Ag}^+)\) pair with hydroxide ions \((\mathrm{OH}^-)\) forming silver hydroxide \((\mathrm{AgOH})\).
• Sodium ions \((\mathrm{Na}^+)\) pair with nitrate ions \((\mathrm{NO}_3^-)\) to produce sodium nitrate \((\mathrm{NaNO}_3)\).

The essence of a double displacement reaction is the swapping of partners between interacting compounds, which results in the formation of new products.

Product stability

Product stability refers to whether a compound formed in a reaction can remain in its current structure or if it will decompose. In the reaction between silver nitrate and caustic soda, silver hydroxide \((\mathrm{AgOH})\) is initially produced. However, silver hydroxide is known to be unstable.

Due to its instability, silver hydroxide will decompose quickly into silver oxide \((\mathrm{Ag}_2\mathrm{O})\) and water. Silver oxide is much more stable compared to silver hydroxide and presents as a solid. This aspect of product stability is crucial in predicting and understanding the ultimate outcome of a chemical reaction.

Balanced chemical equation

A balanced chemical equation is crucial as it ensures the conservation of mass and atoms in a chemical reaction. For the reaction between silver nitrate and caustic soda:

• The initial reactants are 2 molecules of silver nitrate \((2\mathrm{AgNO}_3)\) and 2 molecules of sodium hydroxide \((2\mathrm{NaOH})\).
• Upon reaction, silver oxide \((\mathrm{Ag}_2\mathrm{O})\), sodium nitrate \((2\mathrm{NaNO}_3)\), and water \((\mathrm{H}_2\mathrm{O})\) are formed.

The balanced chemical equation for this entire process is:\[2\mathrm{AgNO}_3 + 2\mathrm{NaOH} \rightarrow \mathrm{Ag}_2\mathrm{O} + 2\mathrm{NaNO}_3 + \mathrm{H}_2\mathrm{O}\]By balancing the equation, we demonstrate the principle of mass conservation, showing that the number of atoms for each element is the same on both sides.