Which describes a double replacement reaction?

A double replacement reaction, also known as a double displacement reaction, involves two ionic compounds reacting in such a way that the ions (or partners) in the compounds exchange places. This type of reaction typically occurs in aqueous solutions where the compounds dissociate into their respective ions. When the reaction takes place, the positive ions from one compound swap with the positive ions from the other compound, resulting in the formation of two new compounds, which may either remain dissolved in the solution or precipitate out as a solid.

For instance, when solutions of silver nitrate and sodium chloride are mixed, the silver ions and sodium ions exchange partners, resulting in the formation of sodium nitrate and silver chloride, the latter of which might precipitate as a solid.

The other choices describe different types of reactions:

• The first choice involves a synthesis reaction where two elements combine to form a single compound.

• The second choice describes a decomposition reaction where a single compound breaks down into multiple products.

• The fourth choice refers to a combustion reaction, typically characterized by a substance reacting with oxygen to produce energy, often violently.

Understanding the characteristics of double replacement reactions helps in predicting the products formed during such reactions and elucidating their applications in various chemical contexts.