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Ch.17 - Acids and Bases
Chapter 17, Problem 101

Determine the [OH] and pH of a solution that is 0.140 M in F.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acid-Base Chemistry

Acid-base chemistry involves the study of the transfer of protons (H+) between species. In this context, fluoride ion (F-) acts as a weak base, which can accept protons from water, leading to the formation of hydroxide ions (OH-) and hydrofluoric acid (HF). Understanding this equilibrium is crucial for determining the concentration of OH- and the resulting pH of the solution.
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Equilibrium Constant (Kb)

The equilibrium constant for the base dissociation reaction (Kb) quantifies the strength of a weak base. For fluoride, the reaction can be represented as F- + H2O ⇌ HF + OH-. The Kb value allows us to calculate the concentration of OH- produced in the solution, which is essential for determining the pH. Knowing Kb is vital for solving the problem accurately.
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pH and pOH Relationship

The pH scale measures the acidity or basicity of a solution, while pOH measures the concentration of hydroxide ions. They are related by the equation pH + pOH = 14 at 25°C. Once the concentration of OH- is determined, pOH can be calculated, and subsequently, pH can be derived. This relationship is fundamental for interpreting the results of the calculations.
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