Final answer:
A compound like aluminum chloride (AlCl₃) dissociates in water to produce one Al³⁺ ion and three Cl⁻ ions, resulting in 3 ions per formula unit.
Step-by-step explanation:
When a compound dissociates in water to produce 3 ions per formula unit, it may be a substance with either one polyatomic ion and two single ions, or three single ions of the same charge. For example, aluminum chloride (AlCl₃) dissociates into one Al³⁺ ion and three Cl⁻ ions. Thus, the balanced equation showing the dissociation of aluminum chloride in water would be AlCl₃ (s) → Al³⁺ (aq) + 3Cl⁻ (aq). While AlCl₃ does not contain a polyatomic ion, it is an example of a substance that produces three ions upon dissociation in water. When dealing with compounds that include polyatomic ions, these ions remain intact during dissolution.