Question

\mathrm{~A}\( solution contains the ionic compounds \)\mathrm{BaCl}_{2}\( and \)\mathrm{NaCl}$. What ionic compound could be added that would remove the barium ions from the solution but not introduce any new kinds of ions?

Short answer

The ionic compound that could be added to the solution to remove barium ions without introducing any new kinds of ions is Sodium Sulfate (Na2SO4).

Step-by-step solution

Understanding the Exercise

The solution contains ions of Barium (Ba), Chloride (Cl), Sodium (Na). The task is to find a compound that when added, will cause the Barium ions to precipitate out. This will happen if a compound is introduced that forms an insoluble compound with Barium.

Identify the Compound

The compound needs to form an insoluble ionic compound with Barium in order to remove it from the solution. From the list of common solubility rules, we know that most sulfate salts are insoluble, which includes Barium sulfate (BaSO4). Therefore, the compound to be added should have sulfate ions in that.

Check for Addition of New Ions

The addition of this compound should not introduce any new ions into the solution. This means that the second ion in the compound should already exist in the solution. We already have Sodium (Na) and Chloride (Cl) ions present. Among these, Sodium Sulfate (Na2SO4) is a soluble compound, so if we add this into the solution, it will dissociate into sodium ions and sulfate ions, causing no new types of ions to be introduced.

Key concepts

Ionic Compounds

Ionic compounds are chemical compounds composed of ions that are held together by electrostatic forces known as ionic bonds. These structures are typically formed when metals and non-metals react, where metal atoms lose electrons to become positively charged cations, and non-metal atoms gain electrons to become negatively charged anions.
For example, in the exercise, we have two such ionic compounds: Barium Chloride ( BaCl_2 ) and Sodium Chloride ( NaCl ). Both involve the transfer of electrons resulting in compounds made up of positive and negative ions.

• Barium Chloride: Contains barium ions ( Ba^{2+} ) and chloride ions ( Cl^{-} ).
• Sodium Chloride: Contains sodium ions ( Na^{+} ) and chloride ions ( Cl^{-} ).

It is important to note that the balance of electrical charges is maintained, meaning the total positive charge is equal to the total negative charge in an ionic compound.

Solubility Rules

Solubility rules help predict whether a compound will dissolve in water. These rules are based on empirical observations about the solubility of various ionic compounds.
In general, compounds containing alkali metal ions (like sodium Na^{+} ) and ammonium ( NH_4^+ ) ions are soluble in water. Chlorides, bromides, and iodides are typically soluble as well, except for those of silver, lead, and mercury.

• Sulfates are usually soluble, with notable exceptions including barium sulfate ( BaSO_4 ), lead sulfate, and calcium sulfate.
• The knowledge of these rules was applied in our solution to predict the precipitation of barium ions by adding sulfate ions.

Understanding these rules is crucial for predicting the outcomes of reactions and is especially helpful for determining which ions remain in solution and which will form a solid precipitate.

Precipitation Reactions

Precipitation reactions are reactions where two soluble salts in aqueous solutions react to form one or more insoluble products, known as precipitates.
This type of reaction is particularly useful in removing specific ions from a solution by forming an insoluble compound. In the given exercise, we were tasked with removing barium ions by creating barium sulfate ( BaSO_4 ) as a precipitate. The precipitation occurs because barium sulfate is insoluble in water according to solubility rules.

• The concept relies on adding a compound that dissociates to provide anions that can react with the cations in the solution to create an insoluble salt.
• By adding sodium sulfate ( Na_2SO_4 ), sulfate ions are introduced that will bind with the barium ions to form the insoluble barium sulfate, thereby removing the barium ions from the solution.

Such reactions not only help purify solutions but also are essential in various industrial and laboratory processes.