CHEM 1120 1nd Edition Lecture 14 Outline of Last Lecture I. Equilibrium calculationsa. Percent ionizationb. Stepwise methodII. Weak bases and their relation to weak acidsa. Kb = [conjugate acid][OH-]/[base]b. Categories of weak basesIII. Relationship between Ka and Kba. Kw = Ka x KbIV. Acid Base properties of Salt solutionsV. Acid Base behavior and chemical structurea. 3 factorsOutline of Current Lecture I. Factors affecting acid strengtha. OxyacidsII. Hydrolysis of metal ionsIII. Leveling effectIV. Lewis Acids and BasesV. Common ion effectThese 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.VI. Buffered solutionsa. Compositionb. How does it work?c. Calculating pHd.Current LectureI. Factors affecting acid strengtha. For a series of oxyacids, acidity increases with the number of oxygenb. Resonance in the conjugate bases of carboxylic acids stabilizes the base and makes the conjugate acid more acidicII. Hydrolysis of metal ionsa. Water donates a proton, end up with hydronium (H30+)b. Not significant for alkali metal or alkaline earth metalsIII. Leveling effecta. Water exerts a “Leveling effect” on any strong acid or base by reacting with it to form the products of water’s autoionizationb. To rank strong acids in terms of relative strength, we must dissolve them in a solvent that is a weaker base than water (for example, acetic acid)IV. Lewis Acids and Basesa. Acid: an electron pair acceptori. H+, BF3, CO2ii. Atoms with an empty valance orbital can be Lewis acidsb. Base: an electron pair donori. OH-, NH3, NF3ii. Anything that could be a bronsted-lowry base is a Lewis baseiii. Lewis bases can interact with things other than protonsc. A Lewis acid need not contain H+ ions, a Lewis base need not contain OH- ionsV. Next Chapter: Chapter 17VI. Common Ion Effecta. Add a salt, how does it affect the reaction b. Common ion: an ion common to two solutesc. Common ion effect: a shift in equilibrium cause by an addition of a common ionVII. Buffered solutionsa. Buffered solutions (buffers): solution that resists pH change when small amounts of acid or base is addedb. Buffer composition: a weak acid and its conjugate base, or a weak base and its conjugate acidc. How does a buffer solution work? If a small amount of hydroxide is added to an equimolar solution of HF in NaF, for example, the HF reacts with the OH- to makeF- and wateri. Similarly, if acid is added, the F- reacts with it to form HF and waterii. If base is added: HX + OH- H20 + X-iii. If acid is added: X- + H+ HXd. Calculating pH of a bufferi. Log [H30] = log Ka + log [HX]/[X-]ii. pH = pKa + log [X-]/[HX]iii. When working with buffers, do ICE tables in moles, not
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