Chem 162-2011 Lecture 9

Chem 162-2011 Lecture 9 - CHEMISTRY 162-2011 LECTURE...

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Unformatted text preview: CHEMISTRY 162-2011 LECTURE 9 (H&P 15.1-15.3) ANNOUNCEMENTS E-MAIL ATTENDANCE • Sign in QUIZ EXAMS Chem 162-2011 Lecture 9 1 PLAN FOR TODAY : CHAPTER 15 ACIDS AND BASES EQUILIBRIUM • The Brønsted-Lowry Theory of Acids and Bases • Molecular Structure and Strengths of Acids and Bases • Self-Ionization of water – the pH Scale Chem 162-2011 Lecture 9 2 pH [H + ] 14 Basic 1x10-14 H 2 O + H 2 O ← → H 3 O + + OH- K w = 1x10-14 7 Neutral (e.g. H 2 O) 1x10-7 K w = [H + ][OH- ] = 1 x 10-14 pH + pOH = 14 K w = K a x K cb = K ca x K b = 1 x 10-14 * *a & b = acid and base; ca & cb = conjugate acid and conjugate base pK a + pK b = 14 Acidic 1x10 o pH units of 1 to 13 is what is commonly used, but pH’s as low as-1 or as high as 15 are possible. No acids in existence for <-1 or bases for >+15. pH = -log[H + ] pH [H + ] [H + ] = 10-pH pOH = -log[OH- ] [OH- ] = 10-pOH pOH [OH- ] Chem 162-2011 Lecture 9 3 p H + p O H = 1 4 pH + pOH = 14 K w = [H + ][OH- ] = 1 x 10-14 K w = [ H + ] [ O H- ] = 1 x 1- 1 4 pOH = -log[OH- ] [OH- ] = 10-pOH pH = -log[H + ] [H + ] = 10-pH REACTIONS OF ACIDS AND BASES WITH WATER Types of acids and bases : Arrhenius: Acids provide hydrogen ions in aqueous solutions (e.g., HCl, acetic acid). Bases provide hydroxide ions in aqueous solutions (e.g., NaOH, Ca(OH) 2 . Bronsted-Lowry: Acids are proton donors (e.g., HCl, acetic acid) Bases are proton acceptors (e.g., NaOH, Ca(OH) 2 , NH 3 ). Amphiprotic [amph = both, as in amphibian (both bios, i.e., both lives, e.g., frogs that live part of their life in water and the other part on land)]; (also: amphoteric): A substance that can be a Bronsted-Lowry acid or base, e.g., HCO 3- (bicarbonate) Acts as acid: HCO 3- + H 2 O → H 3 O + + CO 3 2- Acts as base: HCO 3- + H 2 O → OH- + H 2 CO 3 Note that H 2 CO 3 is acidic, HCO 3- is amphiprotic, and CO 3 2- is basic. Also, note that H 2 O is amphiprotic. Chem 162-2011 Lecture 9 4 CONJUGATE ACIDS AND BASES ET: Discuss Bronsted-Lowry conjugate acid and conjugate base pairs (an acid and base pair in which the two members differ only by one proton). Latin: jugare – joined together (conjugal visits in prison; conjugate double bonds; conjugate verbs). ET: In problem below, first identify acids and bases; then identify acid and base pairs; then identify components of the pair. 14.31 For the following aqueous reaction, identify the acid, the base, the conjugate base, and the conjugate acid. a. HF + H 2 O F- + H 3 O + HF is an acid; F- is its conjugate base. H 2 O is a base; H 3 O + is its conjugate acid. or H 3 O + is an acid; H 2 O is its conjugate base. F- is a base; HF is its conjugate acid. Chem 162-2011 Lecture 9 5 REACTIONS OF ACIDS AND BASES WITH WATER A or CA or B or CB + H 2 O or H 2 O derivative → 2 Products ACID + WATER H H — A + ← → :A- + H H H R—N—H + ← → R—N: H H BASE + WATER H .....
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Chem 162-2011 Lecture 9 - CHEMISTRY 162-2011 LECTURE...

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