What are the relative ion concentrations in an acid solution?

Answer is: more H⁺ ions than OH⁻ ions.

An Arrhenius acid is a substance that dissociates in water to form hydrogen ions or protons.

For example, hydrochloric acid dissociate in aqueous solution to form hydrogen ions (H ⁺) and chloride anion (Cl⁻):

HCl (aq) → H ⁺ (aq) + Cl⁻ (aq).

An Arrhenius base is a substance that dissociates in water to form hydroxide ions (OH⁻).

For example lithium hydroxide is an Arrhenius base:

LiOH (aq) → Li⁺ (aq) + OH⁻ (aq).