41643983-Midterm-Two-Study-Guide

# 41643983-Midterm-Two-Study-Guide - Midterm Two Study Guide...

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Midterm Two Study Guide Key Concepts of Chapter 19 Ionic Equilibria in Aqueous Systems I. Buffers/Concepts A. The Common Ion Effect 1. The process in which there are two dissolved solutes that contain the same ion or ions. The common ion suppresses the ionization of a weak acid or base. a. Exceptions to this rule are the many transition metal compounds because they form complex ions. B. Buffer Solutions 1. A solution that resist changes in the hydronium and hydroxide concentrations when an acid or base is added (lab #3 is a clear example of this). a. Each buffer has a weak acid and conjugate base. (i) Buffer solutions’ capacity: How well does it prevent pH changes from happening? Dependent upon absolute concentrations and the Henderson-Hasselbach equation. C. Henderson-Hasselbach Equation 1. The Equations: pH = pK a + log [A-] / [HA] pOH = pK b + log [BH+] / [B] (i) The salt produced by the reaction will always be on top and the acid will be on the bottom. This equation allows us to predict design our own pH-controlled buffers. 2. Buffer Capacity and Buffer Ranges (i) Buffer capacity of a measure of the ability to resist pH changes and depends on both of the absolute and relative component concentrations. The more concentrated the components of the buffer are, and then the more buffer will have a greater capacity for change. A. Common Indicators 1. Indicators are used to determine pH because of the color changes that occur during a titration. At the pH levels below 4.5, litmus becomes red and when pH is above 8.3, litmus becomes blue. If pH is in between 4.5 – 8.3, then there is mixed color between red and blue. Different indicators are used for different acid-base titrations.

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B. Common Reactions Looked At 1. Strong Acids + Strong Base a. Equivalence point of this reaction’s pH is at 7.0 and the reaction does not form a buffer 2. Weak Acid + Strong Base a. Equivalence point of this reaction’s pH is dependent on the hydrolysis of the solutions and the buffer occurs and forms before the equivalence point 3. Strong Acid + Weak Base a. Equivalence point of this reaction’s pH is dependent on the hydrolysis of the solutions and the buffer occurs and forms after the equivalence point 4. Weak Acid + Weak Base a. AVOIDED in our course because there are too many shifts between buffers that form and the pH changes so many times that it causes the equation to be messy to fix. Therefore, we avoid this whole entire thing. III. Molar Solubility
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41643983-Midterm-Two-Study-Guide - Midterm Two Study Guide...

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