CHEM 113 1st Edition Lecture 23 Outline of Last Lecture- Acid strength of nonmetal hydrides- Acid strength of oxoacids- Hydrated metal ions- Salts that yield neutral solutions- Salts that yield acidic solutions- Salts that yield basic solutionsCurrent Lecture Outline- Acid Base Buffers- Common-ion effect- The Henderson-Hasselbalch EquationCurrent LectureChapter 19: Ionic Equilibria in Aqueous Systems- Acid Base Bufferso An acid-base buffer is a solution that lessens the impact on pH from addition of acid or baseo It will usually consist of a conjugate acid-base pair where both species are present in appreciable quantities in solution. Meaning a buffer is either a solution of a weak acid and its base, or a weak base and its conjugate acid.o * Note an acid that we will probably be seeing a lot is acetic acid (CH3COOH), which is a weak acid and an oxoacid.- Common-ion effecto This is how buffers worko The common-ion effect occurs when a given ion is added to an equilibrium mixture that already contains that ion, and the position of equilibrium shifts away from forming it.o An example of this in action is acetic acid Acetic acid in water dissociates slightly to produce some acetate ionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. The addition of CH3COO- reduces the percent dissociation of the acid. Table 19.1 on page 766 illustrates thiso The shift in equilibrium position absorbs the change in [H3O+] and the pH changes only slightlyo To solve buffer problems, ICE tables may be used like we have seen in the previous chapter. It is important to note that the Small Value Approximation can be applied to these buffer problems.- The Henderson-Hasselbalch Equationo The relationship of the Henderson-Hasselbalch Equation allows us to solve directly for pH instead of having to calculate [H3O+] first.oo Page 770 shows how this equation was derived from the Ka
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