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).

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.