ENCH 213 Lecture Notes - Tris, Buffer Solution, Conjugate Acid
13 Nov 2013
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Monoprotic acid-base equilibria strong acids and bases: weak acids and bases, fraction of dissociation of an acid, buffers, henderson-hasselbalch equation, buffer capacity. H 3o+ + a: ha + h2o, ka = [h3o+][a-]/[ha] log ka = log [h3o+] + log [ha]/[a-] Example: tris buffer buffer prepared by dissolving 12. 43 g b + 4. 67 g bh+cl- in 1. 00 l water. ph = ? ph = pka + log. In the same solution, volume wont affect it. A buffer solution was prepared by mixing 50. 0 ml of a 0. 100 m solution of ch3cooh with 0. 500 grams of nach3coo (82. 034 g/mol). The resulting mixture is diluted to 100. 0 ml. Ka for acetic acid is 1. 75 x 10-5: 4. 84, 7. 67, 4. 97. Ch3cooh : 0. 100mol/l * 0. 0500l = 0. 00500mol = 5. 00 mmol ch3cooh. Ch3coo: 0. 500g * (mol/82. 034g) = 6. 095 mmol ch3co- Molar ratio of [ha]/[a-] = 6. 095/5. 00 = 1. 210 ph = pka + log(1. 219) = -log (1. 75x10-5) + log (1. 219) = 4. 84.
