Chapter 16 Notes
Chapter 16 Notes Chem 106
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This 2 page Class Notes was uploaded by Maranda Butterfield on Wednesday October 7, 2015. The Class Notes belongs to Chem 106 at Washington State University taught by Nathalie Wall in Fall 2015. Since its upload, it has received 18 views. For similar materials see Principles of Chemistry II in Chemistry at Washington State University.
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Date Created: 10/07/15
162 163 164 Chapter 16 Buffer resists pH change by neutralizing added acid of added base It contains either 0 Significant amounts of a weak acid and its conjugate base or 0 Significant amounts of a weak base and its conjugate acid HendersonHasselbalch equation allows us to calculate the pH of a buffer solution from the initial concentrations of the buffer components as long as the x is small approximation is valid base 0 pH pKa log acid There are two parts to calculating pH changes in a buffer solution 0 The stoichiometry calculation where you calculate how the addition changes the relative amounts of acid and conjugate base 0 The equilibrium calculation where you calculate the pH based on the new amounts of acid and conjugate base A buffer is most effective when the concentrations of acid and conjugate base are equal o In order for a buffer to be reasonably effective the relative concentrations of acid and conjugate base should not differ by more than a factor of 10 A buffer is most effective when the concentrations of acid and conjugate base are high 0 The effective range for a buffering system is one pH unit on either side of pKa Buffer capacity the amount of acid or base that you can add to a buffer without causing a large change in pH 0 This increases as the relative concentrations of the buffer components become more similar to each other o It also increases as they become more concentrated Acidbase titration a basicacidic solution of unknown concentration reacts with an acidicbasic solution of known concentration 0 IndicatorpH meter a substance whose colour depends on the pH 0 Equivalence point the point in the titration when the number of moles of base is stoichiometrically equal to the number of moles of acid 0 Page 770779 should really be read Indicators 0 HInaq colorl H20l lt gt H30aq In39aq color2 I If 1 the indicator solution will be intermediate in color If gt 10 the indicator solution will be the color of In I HM lt 01 the indicator solution will be the color of H111 Hm 165 166 167 168 Ksp is the same as before Concentration of products over concentration of reactants 0 Solving for Smoar solubility is the same as solving for the concentration Generally the solubility of an ionic compound is lower in a solution containing a common ion than in pure water Generallt the solubility of an ionic compound with a strongly basic or weakly basic anion increases with increasing acidity Q is calculated same as before KSID at equilibrium 0 If Q lt K the solution is unsaturated and more of the solid ionic compound can dissolve in the solution 0 If Q K the solution is saturated The solution is holding the equilibrium amount of the dissolved ions and additional solid does not dissolve in the solution 0 If Q gt K the solution is supersaturated Under most circumstances the excess solid precipitates out of a supersaturated solution Selective precipitation a process involving the addition of a reagent that forms a precipitate with one of the dissolved cations but not the others QualitativeQuantitative analysis Complex ion contains a central metal ion bound to one or more ligands o Ligand neutral molecule or ion that acts as a lewis base Kf is like any other K This is the formation constant