The reaction [tex]$A B + C D \rightarrow A D + C B$[/tex] involves the exchange of ions between the two compounds AB and CD. Here, A is paired with D, and C is paired with B, indicating that both compounds have swapped their components.
To identify the type of reaction:
1. Synthesis (A): In a synthesis reaction, two or more reactants combine to form a single product, such as [tex]$A + B \rightarrow AB$[/tex]. This is not the case here.
2. Decomposition (B): In a decomposition reaction, a single compound breaks down into two or more simpler substances, such as [tex]$AB \rightarrow A + B$[/tex]. This doesn't match the given reaction.
3. Single Replacement (C): In a single replacement reaction, one element replaces another in a compound, such as [tex]$A + BC \rightarrow AC + B$[/tex]. This does not fit the given reaction either.
4. Double Replacement (D): In a double replacement reaction, the ions of two compounds exchange places, forming two new compounds. This is exactly what we see with [tex]$AB + CD \rightarrow AD + CB$[/tex].
Therefore, the reaction [tex]$A B + C D \rightarrow A D + C B$[/tex] is best described as:
D. Double replacement
