What is the hydroxide ion concentration of the lake described in question 3? a. 10−10 M b. 10−4 M c. 10−7 M d. 10.0 M

Verified step by step guidance

1. Identify the pH of the lake from question 3, as the hydroxide ion concentration is directly related to the pH value.
2. Recall the relationship between pH and pOH in a solution: pH + pOH = 14.
3. Calculate the pOH of the lake by subtracting the pH from 14.
4. Use the formula for pOH to find the hydroxide ion concentration: [OH-] = 10^(-pOH).
5. Match the calculated hydroxide ion concentration with the provided options to find the correct answer.

Key Concepts

pH and Hydroxide Ion Concentration

The pH scale measures the acidity or basicity of a solution, with lower values indicating higher acidity and higher values indicating higher basicity. The concentration of hydroxide ions (OH⁻) is inversely related to the concentration of hydrogen ions (H⁺) in a solution. In pure water at 25°C, the product of H⁺ and OH⁻ concentrations is constant at 1.0 x 10⁻¹⁴ M², allowing for the calculation of one from the other.

Neutrality of Water

Pure water is considered neutral, with a pH of 7, which corresponds to equal concentrations of H⁺ and OH⁻ ions, both at 1.0 x 10⁻⁷ M. This neutrality is a fundamental concept in understanding acid-base chemistry, as it serves as a reference point for determining whether a solution is acidic or basic based on its pH value.

Calculating Hydroxide Ion Concentration

To find the hydroxide ion concentration in a solution, one can use the formula [OH⁻] = 1.0 x 10⁻¹⁴ M² / [H⁺]. If the pH is known, it can be converted to [H⁺] using the formula [H⁺] = 10^(-pH). This relationship allows for the determination of hydroxide ion concentration based on the pH of the solution, which is essential for answering questions related to the acidity or basicity of a lake or any aqueous solution.