IMG_0001_NEW_0004

IMG_0001_NEW_0004 - r^-- "^-*-t-__._t K- _[H-]tA-l...

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siir' €+:. ..ACIDS AND BASES" TODAY'S LECTIJRE: . Buffered Solutrons . Henderson-Hasselbalch Equation . Buffer Capacity Concept of Buffering . Most imporlant example: blood-cell survival Need pH to remain relatively constant aL -7.4 . Buffered solutions are typically: 1) A *,*al' acirl and its,con"iur.latc basc, \________Y- Comes from a salt e.g. {}{rC()L}il }iallllrC(X) >{l{,f{X} 2) A tr,crk batc and its ccn]ilri;'ltt": at:rtl \- --\-/ Comes front a salt e.g. \. i i. ii i lri:t - " \11| Buffered solutions resi,st changes in pH when either OH* or H* ions are added -+ Maintain approximately constant pH Weak Acid Buffer . (ieneral Butfer: Weak Acid and its Salt We:rk acid IJA(aq) -- H+(a(t) Weak acid + S:rlt \{A (aq) -+ M* (.aq) + Salt Cation = Buffer + A-(aq) +.-_. Conjugate base { Comnron lt-tn -, A (oq) Anion (- conjugatc base) .1 Factors afl'ecting the pH
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Unformatted text preview: r^-- "^-*-t-__._t K- _[H-]tA-l =i,r-t=K tFlAl ' fF{Al l' ' "[A] i .___ _*: pl I deterrnineci br': I ) \'aluc olA" lor the acid cornponent of the buf ler l) Tlre ratio of tlie concentrations of the cq4.jqgale acicl base pair' Response to H* and OH-. -\dclition of small amount of strong base--) .-.,:.\ !r,:rtlll.rJ:'," i1h ir llrk ;tciri OLI-(at1) - LA(aq) + A (crc) + HzO(D = [H.\] decreases and [A-] increases Sincc lH l- ^ lHAl = pll rvill increase tAl . -{ddition of small :rmount of strong acid + -.-!:. il:if.l.--,]!-tl) i"r rllt ii.'"r!." {rlr',-' H-(ac1) + A (aq) -+ HA(aq) > [FL{] increases and [A-] decreases = pH will decrease . BUT in Buffel [Hal a1d [A-f nre LARGE = Change in [HA] apd [A ] is very small = Change in [F{A]/[A ] is very small = tttr{ ia: ;al4i1,'u,f ulrell;illg,c't{...
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This note was uploaded on 12/27/2011 for the course CHEM 122 taught by Professor Williams during the Fall '10 term at Simon Fraser.

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