Calculate the [H⁺] for the aqueous solution in which [OH⁻] is 1 x 10⁻⁹. Is this solution acidic, basic or neutral? Show your work
pH + pOH = 14
pH + 9 = 14 ... pH = 5
-log[H⁺] = 5 ... log[H⁺] = -5 ... [H⁺] = 1E-5
pH < 7 means acidic
To determine the concentration of hydrogen ions, [H⁺], we can use the equation for the autoionization of water:
[H₂O] ⇌ [H⁺] + [OH⁻]
In pure water, the concentration of hydrogen ions, [H⁺], is equal to the concentration of hydroxide ions, [OH⁻], which is 1 x 10⁻⁵ M at 25°C. However, in this case, we are given the concentration of hydroxide ions, [OH⁻], which is 1 x 10⁻⁹ M.
Since [H⁺] and [OH⁻] concentrations in the solution must multiply to equal the ion product of water (Kw = 1 x 10⁻¹⁴ at 25°C), we can use this relationship to find [H⁺]:
[H⁺] = Kw / [OH⁻]
[H⁺] = (1 x 10⁻¹⁴) / (1 x 10⁻⁹)
[H⁺] = 1 x 10⁻⁵ M
Therefore, the concentration of [H⁺] in this solution is 1 x 10⁻⁵ M.
To determine whether the solution is acidic, basic, or neutral, we can refer to the pH scale.
Since [H⁺] is greater than [OH⁻], the solution is considered acidic. The pH value for this solution can be calculated as -log[H⁺]:
pH = -log(1 x 10⁻⁵)
pH = 5
Therefore, the solution is acidic with a pH of 5.