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Unformatted text preview: Winter 2010/Chem 109A/LZhang Chapters 1.2 Acids and Bases V. Acids and Bases A. Arrhenius Theory (sec. 1.16-1.17) 1. Acid : a compound that dissociates in water to give hydronium ion ( H 3 O + ) H Cl O H 3 O Cl + + e.g. 1 H H 2. Base : a compound that dissociates in water to give hydroxide ion (OH- ) HO NH 3 e.g. 2 O + H H NH 3 + H 3. Equilibrium constant ( K eq ) : H A H 3 O A + H 2 O + e.g. 3 K eq = ______________________ 4. Acidity constant K a = K eq [H 2 O] = _____________________ 5. p K a = 6. A stronger acid has higher [H 3 O + ] in equilibrium, larger K a , and therefore smaller p K a p K a 1, strong acid, completely dissociated in water p K a ~ 7-15 weak acid p K a > 20 very weak acid, not deprotonated in water 7. Acidity - measured by pH; pH = -log[H 3 O + ]; high [H 3 O + ], low pH 8. Limitation - apply only to aqueous systems B. Brnsted-Lowry Theory: applicable to aqueous and organic solutions (sec. 1.16) 1. Acid : a compound that donates proton (H + ) to give its conjugated base...
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