Chem%20162-2011%20Lecture%209

Chem%20162-2011%20Lecture%209 - CHEMISTRY 162-2011 LECTURE...

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Chem 162-2011 Lecture 9 1 CHEMISTRY 162-2011 LECTURE 9 (H&P 15.1-15.3) ANNOUNCEMENTS E-MAIL ATTENDANCE Sign in QUIZ EXAMS
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Chem 162-2011 Lecture 9 2 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
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Chem 162-2011 Lecture 9 3 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 0 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 - ] pH + pOH = 14 pH + pOH = 14 K w = [H + ][OH - ] = 1 x 10 -14 K w = [H + ][OH - ] = 1 x 10 -14 pOH = -log[OH - ] [OH - ] = 10 -pOH pH = -log[H + ] [H + ] = 10 -pH
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Chem 162-2011 Lecture 9 4 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.
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Chem 162-2011 Lecture 9 5 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.
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