In which type of chemical reaction is writing state symbols such as \((aq)\) and \((s)\) especially useful to show that a solid product has separated from a solution?

Correct answer: Double displacement reactions (precipitation reactions)

State symbols like \((aq)\) (aqueous) and \((s)\) (solid) are especially useful in double displacement (precipitation) reactions. In these reactions, ions in solution exchange partners, and an insoluble product forms. Writing \((s)\) for that product clearly shows that a solid separates out from the aqueous solution.