Final answer:
A double-replacement reaction is a chemical process where the positive and negative ions from two ionic compounds in solution exchange places to form two new compounds, typically resulting in a solid precipitate, gas, or a molecular compound like water.
Step-by-step explanation:
The definition of a reaction involving the exchange of positive ions between two compounds dissolved in water is called a double-replacement reaction or double-displacement reaction. In this type of reaction, the cations (positive ions) and the anions (negative ions) of two different ionic compounds swap partners to form two new compounds. The general form of a double-replacement reaction can be represented as AB + CD → AD + CB, where A and C are cations, while B and D are anions. These reactions typically occur when substances are in an aqueous solution.
For a double-replacement reaction to take place, one of the products is usually a solid precipitate, gas, or a molecular compound such as water, signifying a chemical change has occurred. Double-replacement reactions include precipitation, acid-base, and gas-forming reactions. A common example of an acid-base double-replacement reaction is when an acid reacts with a base, producing water and a salt.