lecture_02_11_10

lecture_02_11_10 - Today Relationship between KA and KB...

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1 02-11-10 Today Relationship between K A and K B Molecular origins of acid/base strength Polyprotic acids Lewis Acids and Bases Chapter 17: Additional Acid/Base Stuff Common ion effect Tuesday (02-16-10) Indicators Titrations Buffer Solutions Announcements: ChemWiki Info Session Today at 4:10-5:00pm in room 179 Relation between K a of an acid and K b of its conjugated base b a w K K K = pK w = pK a + pK b =14 the stronger the acid, the weaker the conjugate base, i.e. the larger K a of an acid, the smaller K b of its conjugate base the stronger the base, the weaker the conjugate acid, i.e. the larger K b of a base, the smaller K a of its conjugate acid calculate pK a from pK b and vice versa ClO 2 ¯ HClO 2 Acids and their conjugate bases OAc¯ HOAc HOCl ClO¯ NH 4 + NH 3 pK b pK a CH 3 NH 3 + CH 3 NH 2
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2 Example Calculate the pH of a solution 0.1 M solution of ammonium chloride (NH 4 Cl) in water. pK B (NH 3 )=4.75. NH 4 + (aq) + H 2 O(l) H 3 O + (aq) + NH 3 (aq) Initial 0.1 ~0 0 Equilibrium 0.1-x x x Cl¯(aq) + H 2 O(l) HCl (aq) + OH¯ (aq) pK a =pK W -pK A = 14-4.75 = 9.25 x x K A = 1 . 0 2 K A = 10 -9.25 = 5.6 x 10 -10 Shortcut: when x<<<0.1, then 1 . 0 2 x K A = and 6 10 10 48 . 7 10 6 . 5 1 . 0 1 . 0 = = = x x x K x A pH=5.13 What makes acids strong ?
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This note was uploaded on 02/16/2010 for the course CHEM 35991 taught by Professor Osterloh during the Spring '10 term at UC Davis.

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lecture_02_11_10 - Today Relationship between KA and KB...

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