Lecture 29 - water and solutes

Lecture 29 - water and solutes - = [H+] [- OH] water is...

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Bufferin g: What makes a good buffer, a weak or strong electrolyte? • The ability of a solution to resist changes in pH.
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Weak Electrolytes: Consider an organic acid HA that dissociates into H+ and A- HA < -- > H+ + A- Then the concentration of HA can be determined from the equilibrium equation: [H+][A-] Keq = ------------ [HA] [ ] = concentration in molarity (moles/liter)
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Definition of acids and bases (Lowry and Bronsted) Acid – proton donor Base – proton acceptor Lactic acid < -- > lactate - + H+ Lactic acid is a weak acid Lactate is a conjugate base For acids, the Keq is expressed as the pK pK = log 1/ Keq
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Water is a weak electrolyte: HOH < -- > H+ + -OH (note: physiologically, H+ = H3O) [H+] [- OH] Keq = 1.8 x 10-16 = __________ [H20] Keq x [H20]
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Unformatted text preview: = [H+] [- OH] water is 55.5 M, Keq x 55.5 M = 1 x 10 14 (at 25 oC) = ion product of water (a constant). Since [H+] = [- OH], then [H+] = 1 x 10 7 M Definition of pH A convenient way to express [H+] is by pH: pH = log 1/[H+] pOH = log 1/[- OH] pH + pOH = 14 Henderson-Hasselbalch Equation Relates pH to concentrations of conjugate acids and bases. Conjugate acid < -- > conjugate base + H+ [H+] [conjugate base] Keq = ----------------------------[conjugate acid] 1 1 [conjugate base]------ = ----- --------------------[H+] [Keq] [conjugate acid] 1 1 [conjugate base] log ------ = log ----- + log --------------------[H+] [Keq] [conjugate acid] [conjugate base] pH = pK + log --------------------[conjugate acid]...
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This note was uploaded on 11/20/2011 for the course NS 3200 at Cornell University (Engineering School).

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Lecture 29 - water and solutes - = [H+] [- OH] water is...

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