Question

What type of reaction is the following? (Chapter 9\()\) \(\mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{aq})+\mathrm{BaCl}_{2}(\mathrm{aq}) \rightarrow 2 \mathrm{KCl}(\mathrm{aq})+\mathrm{BaCO}_{3}(\mathrm{s})$$ \begin{array}{l}{\text { a. combustion } \quad \text { c. single-replacement }} \\ {\text { b. double-replacement } \text { d. synthesis }}\end{array}\)

Short answer

The given reaction is a double-replacement reaction.

Step-by-step solution

Identify the reactants and products

In the given reaction, the reactants are \(\mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{aq})\) and \(\mathrm{BaCl}_{2}(\mathrm{aq})\). The products are \(2 \mathrm{KCl}(\mathrm{aq})\) and \(\mathrm{BaCO}_{3}(\mathrm{s})\).

Analyze the reaction

Since both reactants are ionic compounds and are reacting to form two new ionic compounds as products, we can look for any transfer of ions between the reactants: In the reactants, the ions are \(\mathrm{K}^+\), \(\mathrm{CO}_{3}^{2-}\), \(\mathrm{Ba}^{2+}\), and \(\mathrm{Cl}^-\). In the products, the ions are \(\mathrm{K}^+\), \(\mathrm{Cl}^-\), \(\mathrm{Ba}^{2+}\), and \(\mathrm{CO}_{3}^{2-}\). Comparing the reactants and products, we can see that the positive ions are switched between the compounds: - \(\mathrm{K}^+\) in \(\mathrm{K}_{2}\mathrm{CO}_{3}\) is now paired with \(\mathrm{Cl}^-\) in \(\mathrm{KCl}\). - \(\mathrm{Ba}^{2+}\) in \(\mathrm{BaCl}_{2}\) is now paired with \(\mathrm{CO}_{3}^{2-}\) in \(\mathrm{BaCO}_{3}\).

Identify the type of reaction

Based on the ion switching observed in the reaction, we can conclude that this is a double-replacement reaction. Therefore, the answer is: b. double-replacement

Key concepts

Double-Replacement Reaction

A double-replacement reaction is a type of chemical reaction where two compounds exchange their components, typically ions, resulting in the formation of two new compounds. This process is like a dance swap, where the partners change places with each other. You are often dealing with two ionic compounds and the positive ions switch places between the compounds. It is crucial to identify the ions involved to see how they rearrange.

• Two reactants: usually ionic compounds in aqueous solution
• Exchange of ions
• Two new products formed

For example, in the reaction \( \mathrm{K}_{2} \mathrm{CO}_{3} + \mathrm{BaCl}_{2} \rightarrow 2 \mathrm{KCl} + \mathrm{BaCO}_{3} \),

• The \( \mathrm{K}^+ \) ion swaps with the \( \mathrm{Ba}^{2+} \) ion.
• The \( \mathrm{CO}_{3}^{2-} \) ion pairs with \( \mathrm{Ba}^{2+} \), forming \( \mathrm{BaCO}_{3} \).

The swapping of partners results in new compounds, distinguishing double-replacement reactions from other types.

Ionic Compounds

Ionic compounds are substances made up of ions, which are charged particles that form when atoms gain or lose electrons. Typically, they consist of positive ions (cations) and negative ions (anions) held together by strong ionic bonds.
These compounds usually form crystalline solids at room temperature and often dissolve in water to produce conducting solutions because ions are free to move. Here’s what you should know about them:

• Formed through ionic bonds between metals and non-metals.
• High melting and boiling points.
• Conduct electricity when dissolved in water.
• Usually appear as solid crystals.

In the context of reactions, recognizing ionic compounds helps you predict the behavior of ions, especially in reactions like double-replacement, where ion exchange plays a big role.

Ion Exchange

Ion exchange is the process where ions in a compound are replaced by different ions, which often occurs in double-replacement reactions. This exchange governs how the reactions proceed and dictates the compounds that result.
In the context of chemical reactions, particularly double-replacement reactions, understanding ion exchange is crucial as it allows for predicting the outcomes of reactions:

• Ions shift partners, leading to new compound formation.
• Often the driving force in solutions is the formation of a precipitate, gas, or weakly soluble compound.

In our example of \( \mathrm{K}_{2} \mathrm{CO}_{3} + \mathrm{BaCl}_{2} \rightarrow 2 \mathrm{KCl} + \mathrm{BaCO}_{3} \),
ion exchange happens as the \( \mathrm{K}^+ \) ions in the carbonate switch with the \( \mathrm{Ba}^{2+} \) ions in barium chloride, leading to the formation of potassium chloride and barium carbonate as the products. Understanding ion exchanges helps in balancing reactions and predicting product formation.