Question

An aqueous solution contains silver nitrate. Which of the following substances could be added to this solution to precipitate the silver ions as silver chloride? (a) \(\mathrm{Cl}_{2}(g)\) (b) \(\mathrm{NaCl}(s)\) (c) \(\mathrm{PbCl}_{2}(s)\) (d) \(\mathrm{CCl}_{4}(D)\)

Short answer

The substance that can be added to the aqueous solution of silver nitrate to precipitate the silver ions as silver chloride is \(\mathrm{NaCl}(s)\).

Step-by-step solution

Analyze \(\mathrm{Cl_{2}(g)}\)

\(\mathrm{Cl_{2}(g)}\) is a diatomic molecule of chlorine gas. In solution, it does not generate \(Cl^{-}\) ions directly, but rather undergoes a multi-step reaction to produce \(HCl\) which can generate \(Cl^{-}\). However, this is not a direct source of \(Cl^{-}\) ions.

Analyze \(\mathrm{NaCl}(s)\)

\(\mathrm{NaCl}(s)\) is sodium chloride, a salt. It is highly soluble in water and will readily dissociate into \(Na^{+}\) and \(Cl^{-}\) ions. The presence of \(Cl^{-}\) ions will react with \(Ag^{+}\) ions from silver nitrate to form \(AgCl\) precipitate.

Analyze \(\mathrm{PbCl_{2}(s)}\)

\(\mathrm{PbCl}_{2}(s)\) is lead(II) chloride, an insoluble solid. It cannot dissociate into ions in the solution, thus it cannot provide \(Cl^{-}\) ions to form \(AgCl\) precipitate.

Analyze \(\mathrm{CCl}_{4}(D)\)

Carbon tetrachloride \(\mathrm{CCl}_{4}(D)\) is a covalently bonded substance and does not dissociate in water. As a result, it will not provide \(Cl^{-}\) ions to form \(AgCl\) precipitate.

Key concepts

silver nitrate

Silver nitrate, represented chemically as \text{AgNO}_{3}$, is a salt that dissolves in water to form a solution that contains silver ions (\(Ag^{+}\)) and nitrate ions (\(NO_{3}^{-}\)).
Silver nitrate is commonly used in precipitation reactions due to its ability to easily release silver ions into a solution.
These silver ions are crucial for the formation of precipitates when they encounter other anions that form insoluble compounds with silver.
In many laboratory experiments and real-world applications, silver nitrate is utilized to detect anions like chloride (\(Cl^{-}\)) which can form precipitates. This property makes silver nitrate a valuable reagent in various analytical chemistry processes. Here is how silver nitrate behaves in solution:

• When dissolved in water, silver nitrate dissociates completely.
• The dissociation releases \(Ag^{+}\) ions which are active in forming precipitates.
• Nitrate ions (\(NO_{3}^{-}\)) do not form a precipitate with most common cations.

This makes silver nitrate easy to use and very effective in precipitation reactions where detecting specific anions is desired.

silver chloride

Silver chloride, represented as \text{AgCl}$, is a white, insoluble solid that forms during certain chemical reactions.
It is produced when silver ions (\(Ag^{+}\)) in solution react with chloride ions (\(Cl^{-}\)).
This reaction is a classic example of a precipitation reaction, where two ions combine to form a solid compound that is not soluble in water. Here's what you should know about the formation of silver chloride:

• Silver chloride forms when solutions containing \(Ag^{+}\) and \(Cl^{-}\) ions are mixed.
• The reaction is represented by the equation: \(Ag^{+} + Cl^{-} \rightarrow AgCl(s)\).
• This white solid is often used in photographic processes and as an antimicrobial agent.

In experiments, silver chloride serves as a reliable indicator of the presence of chloride ions in solution. Because it is insoluble, it settles to the bottom of the container, clearly visible to the observer.

chloride ions

Chloride ions (\(Cl^{-}\)) are negatively charged ions that are crucial in many chemical reactions. These ions are a derivative of hydrochloric acid but can be sourced from different compounds such as sodium chloride (NaCl), which dissociates readily in water to provide \(Cl^{-}\) ions.
Here are key points about chloride ions:

• They are essential for body fluids and maintain a proper balance of water and other nutrients in the body.
• They react with \(Ag^{+}\) ions to form an insoluble precipitate, \(AgCl\). This makes them important for analytical chemistry experiments where detecting silver or chloride is necessary.
• Common sources of chloride ions include sodium chloride and hydrochloric acid.

To create a precipitation reaction with silver ions, a suitable source of chloride ions, like sodium chloride, needs to be added to the solution.
This will cause the silver ions and chloride ions to react, resulting in a visible precipitate of silver chloride. This process is often used as a test for chloride ions in unknown solutions.