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IMG_0001_NEW_0006_001 - [A or $A is 10 x bigger than the...

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The Henderson-Hassel balch Eq uation Proton concentration: [H*] = K" ffi Take -log,,, of both sides log[ H l: - tog( K", - .*[H$'l ' l' "1, tA-] , pH=pK.."-lffiiJ Important approximations : ll l: I11 ilg Lll{l = rl1Alu Acceptable because: - Change in [A-] and [HA] from addition of small amount of strong acid or base - [A-],, and lHAl., are large = cl-iange ir-rsignificant Buffer Capacity pH = pA. * rosl +l -[iHA] , I'Ion,do ue minimise changes to [A-]/[HA]? l{ethocl 2: Make [A-] : [HAl -+ optimum buffering fbr added strong acid Oll strong base ir[A ]: tFiAl pH: pK. + log(1) = For optimurn bufl-eling. select rveak acid with pK. as close as possible to desired pH Generally, if concentration
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Unformatted text preview: [A ] or $A] is 10 x bigger than the other -> poor butfering Buffer Capacity Buft-er capacity: amount of FI* or OH bufler can absorb without a significant change in pH pH = pK. ..rIsr+'l "I tFrA], How do we minimise changes to [A-]/lFIAl? Method l: Make [A-] and [HAl LARGE Larger [A-] and tHAl : Larger Capacity Relative change in [A ] and IFIAI r,vith addition of [OH-] or [H*] smaller > Change in [A ]/[F{A] smaller 1 t ''l ^it ,.,1{ :i, f,F,"' 1l'', 1':: ' 'l' ' . - tt; l . ,t ,z h.- i Lr l\ r. ! ' ,,7 tt b) .i.i ; t,r-,,jt 'i 1l--r l^. i:! I J "- 1 t,l ; /t l'4 l' . i-i / /": { t: l! /. t' .) r'l ) ,-,'1, ll, t : i" : '' j I .t r 1,, r...
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