How to know whether the non spectator ion or the base/acid is the reactant

[Caleb Kim 1K]

I was dealing with salt buffer problems, where an acid or base was given a concentration and the conjugate was also given a concentration. I was wondering how to know which one was the reactant and which one was the product?

[Tiffany Wang 3L]

I think the one that dissociates or gets protonated in water to produce the other conjugate acid or base is the reactant. Your product will be the conjugate acid or base and hydronium or hydroxide ions.