BCHE 395-3 2013 pH Buffers Titrations

Thinkquestorgc006669datachemequilibriumkahtml acids

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Unformatted text preview: acid/base –  www.science.uwaterloo.ca/~cchieh/cact/c123/stacids.html •  Discussion and problems –  mccord.cm.utexas.edu/courses/summer2005/ch302/strong.html •  List of strong acids and bases Acids & Bases acid •  Acid: substance that donates protons –  HA : ex. (- COOH, - NH3+) •  Base: substance that accepts protons –  A- : ex. (- COO- , - NH2) •  Strong acids and bases completely ionize (100%) in aqueous soluYons •  HA + H2O à༎ H3O+ + A- or… Note the arrows! •  (acid) HA à༎ H+ + A- (base) •  Concept of conjugate acid- conjugate base pairs base library.thinkquest.org/C006669/data/Chem/equilibrium/ka.html Acids & Bases Keq = [H+][A- = Ka [HA] •  Ka = acid dissociaYon constant •  Stronger the acid, the larger the dissociaYon constant: Ka > 1 – Associate this with the Ka equaYon – Strongest acids completely dissociate – Ka is immeasurable large ex. HCl •  For convenience pKa = - log Ka Know it! Acids & Bases Keq = [H+][A- = Ka [HA] •  Strength of an acid is a measure of its tendency to release a proton •  Use Ka acid dissociaYon constant (M)   HA ⇔ H+ + A- (incomplete dissociaYon) –  Ka measured at 25°C Weak Acids & Bases •  Weak acids and bases dissociate incompletely in aqueous soluYons –  Only par2ally ionized in aqueous solu2ons –  Ka < 1 •  HA ⇔ H+ + A– •  Since [HA] ≠ [H+], need to consider the degree of dissociaGon in order to calculate pH •  Most acids and bases in biological systems are classified as weak Weak Acids...
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This note was uploaded on 03/02/2014 for the course BIOCHEMIST 395 taught by Professor Potenza during the Spring '14 term at NMSU.

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