In an acid solution, which statement best describes the relative ion concentrations?

In an acid solution, which statement best describes the relative ion concentrations?

• A. Fewer H+ than OH-
• B. An equal number of H+ ions and OH- ions
• C. H+ ions, but no OH- ions
• D. More H+ ions than OH- ions

Answer: (D)

In aqueous solutions, acids raise the concentration of hydrogen ions, while water’s autoionization ensures there is always some hydroxide present. The product [H+][OH-] equals 1.0×10^-14 at room temperature, so when [H+] is high, [OH-] must be present but at a much lower level. This means an acidic solution has more hydrogen ions than hydroxide ions. If there were fewer hydrogen ions than hydroxide ions, the solution would be basic. If the concentrations were equal, the solution would be neutral. The idea of hydrogen ions existing with no hydroxide ions contradicts the constant Kw for water, since some OH- must remain even in acidic solutions.

In aqueous solutions, acids raise the concentration of hydrogen ions, while water’s autoionization ensures there is always some hydroxide present. The product [H+][OH-] equals 1.0×10^-14 at room temperature, so when [H+] is high, [OH-] must be present but at a much lower level. This means an acidic solution has more hydrogen ions than hydroxide ions.

If there were fewer hydrogen ions than hydroxide ions, the solution would be basic. If the concentrations were equal, the solution would be neutral. The idea of hydrogen ions existing with no hydroxide ions contradicts the constant Kw for water, since some OH- must remain even in acidic solutions.