Ion Concentration in Aqueous Solution: Finding the Hydroxide Ion Concentration

What is the hydroxide ion concentration of a 25°C aqueous solution with a hydronium ion concentration of 6.8×10⁻⁴ M?

Select the correct answer below:
a) 6.8 x 10^-18
b) 1.5 x 10^-11
c) 6.8 x 10^-1

Final answer:

The hydroxide ion concentration is approximately 1.5 x 10⁻¹¹

Explanation: This question is related to the concept of ion concentration in an aqueous solution, which is a part of acid-base equilibrium in chemistry. To find the hydroxide ion concentration of a solution when the hydronium ion concentration is given, we use the ion product of water at 25°C, which is 1.0 x 10⁻¹⁴.

To determine the hydroxide ion concentration, you would use the following formula:
[OH-] = Kw / [H3O+]
where Kw is the ion product of water and [H3O+] is the concentration of hydronium ions. Substituting the values in, you get:
[OH-] = 1.0 x 10⁻¹⁴ / 6.8 x 10⁻⁴
This gives an answer of approximately 1.5 x 10⁻¹¹ M. Therefore, the correct option is (b) 1.5 x 10⁻¹¹.