- Examine the reactants (\(\text{NaCl}\) and \(\text{CuSO}_4\)) and products (\(\text{Na}_2\text{SO}_4\) and \(\text{CuCl}_2\)) to identify the ions involved.
- Recognize that the cations (\(\text{Na}^+\) and \(\text{Cu}^{2+}\)) and anions (\(\text{Cl}^-\) and \(\text{SO}_4^{2-}\)) trade partners, forming two new ionic compounds.
- Match this exchange pattern to the general form of a double replacement reaction: \(AB + CD \rightarrow AD + CB\).
- Conclude that the chemical equation represents a \(\boxed{\text{double replacement reaction}}\).
Explanation
- Analysis of Reactants and Products
To identify the type of chemical reaction given by the equation \(2\text{NaCl(aq)} + \text{CuSO}_4\text{(aq)} \rightarrow \text{Na}_2\text{SO}_4\text{(aq)} + \text{CuCl}_2\text{(s)}\), we first analyze the reactants and the products. We have two reactant compounds, sodium chloride (\(\text{NaCl}\)) and copper sulfate (\(\text{CuSO}_4\)). These compounds dissociate into ions in an aqueous solution: sodium ions (\(\text{Na}^+\)), chloride ions (\(\text{Cl}^-\)), copper ions (\(\text{Cu}^{2+}\)), and sulfate ions (\(\text{SO}_4^{2-}\)).
- Observing the Exchange of Ions
Next, we observe how these ions are arranged in the products. The products are sodium sulfate (\(\text{Na}_2\text{SO}_4\)) and copper chloride (\(\text{CuCl}_2\)). By comparing the ions in the reactants to the ions in the products, we can see that the cations (\(\text{Na}^+\) and \(\text{Cu}^{2+}\)) have swapped their original anion partners (\(\text{Cl}^-\) and \(\text{SO}_4^{2-}\)). Specifically, \(\text{Na}^+\) has paired with \(\text{SO}_4^{2-}\) and \(\text{Cu}^{2+}\) has paired with \(\text{Cl}^-\).
- Classification of the Reaction
We can now match this behavior to the standard chemical reaction types:
- Synthesis: Two or more substances combine to form a single product (\(A + B \rightarrow AB\)).
- Decomposition: A single substance breaks down into two or more simpler substances (\(AB \rightarrow A + B\)).
- Single Replacement: One element replaces another in a compound (\(A + BC \rightarrow AC + B\)).
- Double Replacement: The ions of two compounds exchange places in an aqueous solution to form two new compounds (\(AB + CD \rightarrow AD + CB\)).
The reaction \(2\text{NaCl} + \text{CuSO}_4 \rightarrow \text{Na}_2\text{SO}_4 + \text{CuCl}_2\) perfectly fits the pattern \(AB + CD \rightarrow AD + CB\), where \(\text{Na}^+\) (A), \(\text{Cl}^-\) (B), \(\text{Cu}^{2+}\) (C), and \(\text{SO}_4^{2-}\) (D) participate in the exchange. Therefore, this is a double replacement reaction.
Examples
Double replacement reactions are vital in our everyday lives, particularly in water treatment and analytical chemistry. For example, when hard water containing dissolved calcium ions (\(\text{Ca}^{2+}\)) is treated with sodium carbonate, a double replacement reaction occurs, resulting in the precipitation of calcium carbonate (\(\text{CaCO}_3\)), which can then be easily removed. This process helps soften water by removing the mineral ions that cause scaling in pipes and appliances. Understanding these reactions allows chemists to design effective purification methods and create useful materials through selective precipitation.