Final answer:
The hydroxide ion concentration in the aqueous solution is approximately 1.5 x 10^-6 M.
Step-by-step explanation:
In order to determine the hydroxide ion concentration (OH-) in an aqueous solution, you can use the concept of the ion product of water (Kw). At 25 °C, Kw is equal to 1.0 x 10^-14 M^2. The relationship between hydrogen ion concentration (H+) and hydroxide ion concentration (OH-) in a neutral solution is expressed by the equation [H+][OH-] = Kw. Therefore, if the hydrogen ion concentration (H+) is 6.7 x 10^-9 M, we can rearrange the equation to solve for the hydroxide ion concentration (OH-).
[H+][OH-] = Kw
[6.7 x 10^-9 M][OH-] = 1.0 x 10^-14 M^2
[OH-] = 1.0 x 10^-14 M^2 / [6.7 x 10^-9 M]
[OH-] ≈ 1.5 x 10^-6 M
The hydroxide ion concentration (OH-) in the aqueous solution is approximately 1.5 x 10^-6 M.