Week 8- Buffers
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This 1 page Class Notes was uploaded by BettyAnn Mead on Monday March 30, 2015. The Class Notes belongs to 112 at University of Massachusetts taught by Voigtman in Spring2015. Since its upload, it has received 83 views.
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Date Created: 03/30/15
Generally HAH20AH30 0 HA Weak Acid 0 A Conjugate Base Ka H30AHAH30 CBA KaH30 AIHA Take the log of both sides logKaogH30logAHA ogKaogH30logAHA pKapHlogAHA pHpKalogIA1HA If you just have a solution of weak acid it contains very little conjugate base If you just have a solution of the conjugate case it contains very little weak acid BUT we can deliberately prepare solutions that contain signi cant concentrations of BOTH a weak acid AND its conjugate case and such solutions are called buffers Buffers resist changes in their pH when acid or base is added to them pH Effect on Buffers Suppose 1L of buffer with 1M of HAc and 1M of Ac pH474 What happens to the pH if 1mL of 01M NaOH is added Moles of HAc 1L x 1M 1 mole Moles of OH 1mL x 01M 01 m mole HAcOHAcH20 KKaKw KKaKw18E510E1418E9 Qualitativer Neutralized Thus 01m mole of HAc will be neutralized to yield an additional 01m mole of Ac pHpKalog moles Acmoles HAc 474og 10001 moles of Ac09999 moles of HAc474 IF conjugate case10 x weak acid pHpKalog10pKa1 IF weak acid10 x conjugate base pHpKalog110pKa1 OPTIMUM BUFFERING IS AT conjugate baseweak acid THEN pHpKa