Final answer:
In a double-replacement reaction, the correct answer is d) Reactants exchange ions. This involves cations and anions from two compounds switching partners to form new compounds, often in aqueous solutions, without any change in oxidation numbers.
Step-by-step explanation:
In a double-replacement reaction, the products result from the exchange of ions between the reactants. Specifically, the correct answer to what change happens to a product/reactant in double replacement is d) Reactants exchange ions.
This reaction involves two compounds where the cations and the anions swap partners to form two new compounds. An example is AB + CD → AD + BC, where A and C are positively-charged cations and B and D are negatively-charged anions. These reactions often occur in aqueous solutions and can produce a solid precipitate, a gas, or a different molecular compound.
It is important to note that in double-replacement reactions, changes in oxidation numbers do not occur as the exchange involves the physical swapping of ions, not electrons.