Two - Water pH buffers

Two - Water pH buffers - 1/23 and 1/25/12 MCB 2000 Lectures...

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Unformatted text preview: 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 What chemical properties contribute to waters uniqueness? Part 2 1. Polarity and H-bonding 2. Reversible ionization 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 Water, pH, Buffers Lecture Outline Water: common but so unique Chemical properties that contribute to its uniqueness pH Definition of pH Ionization of water as the basis for pH scale Equilibrium reactions Henderson-Hasselbalch equation Titration curves and pK a Buffers Definition How do they work? What determines their effectiveness? Importance of buffers in physiology; consequences of failure in regulation 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 Water undergoes reversible ionization: Equilibrium constant (K eq ) [H+][OH-] [ H 2 0 ] K eq = 1.8 x 10-16 = [H+][OH-] [H 2 O] 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 This small value of K eq indicates that the actual number of dissociated molecules is very small relative to the number of undissociated. Thus the concentration of H 2 O is unchanged. The equation becomes: K eq = 1.8 x 10-16 = [H+][OH-] [55.5 M] [55.5 M] [1.8 x 10-16 ] = [H+][OH-] 1 x 10-14 M 2 = [H+][OH-] 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 K w = 1 x 10-14 = [H+][OH-] This property of water is central to its role as a biological solvent. The ion product of water, K w , is a constant . 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 The pH scale is derived from the ionization of water 1 x 10-14 = [H+][OH-] pH is defined as -log [H+] pH ranges from 0-14 Note that the pH scale is logarithmica difference of 1 pH unit means that a solution has 10X [H + ] than the other. 1/23 and 1/25/12 MCB 2000 Lectures 2 & 3 Why are we concerned about pH in biological systems? biological systems?...
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Two - Water pH buffers - 1/23 and 1/25/12 MCB 2000 Lectures...

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