Which of the following represents a double displacement reaction?

A double displacement reaction, also known as a double replacement or metathesis reaction, occurs when two compounds react and exchange their components to form two new compounds. In the provided example of AgNO₃ and NaCl reacting, the silver ion (Ag⁺) from silver nitrate and chloride ion (Cl⁻) from sodium chloride exchange partners, resulting in the formation of silver chloride (AgCl) and sodium nitrate (NaNO₃).

This reaction typically takes place in an aqueous solution where one of the products (in this case, silver chloride) may precipitate out of the solution, which is a common characteristic of double displacement reactions.

The context of this question involves understanding the nature of the reactants and products. Other reactions listed do not fit the criteria for a double displacement because they either involve the combining of elements to form a compound (as in the first and last examples) or the reaction of an acid with a base to produce a salt and water (the third example, which is classified as a neutralization reaction rather than a double displacement). This understanding of chemical reaction types is essential in recognizing and classifying chemical reactions accurately.