Lecture_Ch17F11_acid-base equilibria

Lecture_Ch17F11_acid-base equilibria - Chapter 17 Acid-base...

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Unformatted text preview: Chapter 17 Acid-base equilibria in aqueous solutions Proton transfer and the Brnsted-Lowry acid-base definition. (acid, H + donor) (base, H + acceptor) HCl H 2 O + Cl- H 3 O + + Lone pair binds H + (base, H + acceptor) (acid, H + donor) NH 3 H 2 O + NH 4 + OH- + Lone pair binds H + An acid is a proton (H + ) donor and a base is a proton acceptor Brnsted-Lowry Acid-Base Definition An acid is a proton donor, any species which donates a H + . A base is a proton acceptor, any species which accepts a H + . Table: The Conjugate Pairs in Some Acid-Base Reactions Base Acid + Acid Base + Conjugate Pair Conjugate Pair Reaction 4 H 2 PO 4- OH- + Reaction 5 H 2 SO 4 N 2 H 5 + + Reaction 6 HPO 4 2- SO 3 2- + Reaction 1 HF H 2 O + F- H 3 O + + Reaction 3 NH 4 + CO 3 2- + Reaction 2 HCOOH CN- + HCOO- HCN + NH 3 HCO 3- + HPO 4 2- H 2 O + HSO 4- N 2 H 6 2+ + PO 4 3- HSO 3- + Weak acid: HA( aq ) + H 2 O( l ) H 2 O + ( aq ) + A- ( aq ) Strong acid: HA( g or l ) + H 2 O( l ) H 2 O + ( aq ) + A- ( aq ) Equilibrium constants for weak acids and weak bases: K a and K b The Acid-Dissociation Constant Weak acids dissociate very slightly into ions in water. Strong acids dissociate completely into ions in water. HA( g or l ) + H 2 O( l ) H 3 O + ( aq ) + A- ( aq ) HA( aq ) + H 2 O( l ) H 3 O + ( aq ) + A- ( aq ) K c >> 1 K c << 1 K c = [H 3 O + ][A- ] [H 2 O][HA] K c [H 2 O] = K a = [H 3 O + ][A- ] [HA] stronger acid higher [H 3 O + ] larger K a smaller K a lower [H 3 O + ] weaker acid ACID STRENGTH Relative acid-base strength and the net direction of reactions...
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This note was uploaded on 01/19/2012 for the course CHEM 1100 taught by Professor Mcintosh during the Fall '08 term at Rensselaer Polytechnic Institute.

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Lecture_Ch17F11_acid-base equilibria - Chapter 17 Acid-base...

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