What does a replacement reaction typically involve?

A replacement reaction typically involves the exchange or replacement of ions within compounds. This is characterized by one element or ion being replaced by another in a chemical reaction, often resulting in the formation of new compounds. For example, in a single displacement reaction, one element displaces another in a compound, leading to a new compound and a free element.

In double replacement reactions, ions in two compounds swap places, forming two new compounds. This type of reaction is common in aqueous solutions where ionic compounds dissolve and interact.

The other options do not accurately describe the nature of a replacement reaction. The combination of two elements refers to synthesis reactions, while the formation of a single compound also signifies synthesis rather than replacement. The synthesis of new elements is not relevant in the context of replacement reactions, as replacement does not involve creating new elements, but rather the rearrangement of existing ions or atoms within compounds.