Unless otherwise stated, all images in this file have been reproduced from: Blackman, Bottle, Schmid, Mocerino and Wille,      Chemistry, 2007 (John Wiley)      ISBN: 9 78047081 0866

A/Prof Adam Bridgeman (Series 1) Dr Feike Dijkstra (Series 2) CHEM1002 [Part 2] A/Prof Adam Bridgeman (Series 1) Dr Feike Dijkstra (Series 2) Weeks 8 – 13 Office Hours: Monday 2-3, Friday 1-2 Room: 543a e-mail: adam.bridgeman@sydney.edu.au e-mail: feike.dijkstra@sydney.edu.au It is a good idea if all lecturers can make an appearance for the first lecture. Remind students we are IT for the rest of the semester. DEMOS for this lecture: EXP 2.3: “Charles law (2.3), EXP 2.1 “CO2 density (2.1)

Acids and Bases Lecture 1: Common Acids and Bases Definitions Equilibria Conjugate acid-base pairs Autoionisation of water pH Blackman Chapter 11, Sections 11.1-11.3 Reproduced from ‘The Extraordinary Chemistry of Ordinary Things, C.H. Snyder, Wiley, 2002 (Page 245)

Use of Common Acids and Bases Substance Formula Use Acids Acetic acid CH3COOH flavouring; preservative Citric acid C6H8O7 flavouring Phosphoric acid H3PO4 rust remover Boric acid B(OH)3 mild antiseptic; insecticide Hydrochloric acid HCl brick/ceramic tile cleaner Bases Sodium hydroxide NaOH oven cleaner Ammonia NH3 household cleaner Sodium carbonate Na2CO3 water softener; grease remover Sodium hydrogen NaHCO3 fire extinguisher; baking powder carbonate Reproduced from ‘The Extraordinary Chemistry of Ordinary Things, C.H. Snyder, Wiley, 2002 (Page 231)

Definitions Arrhenius: H+(aq) + OH-(aq) H2O(l) ACID: H+ producer in aqueous solution e.g. HCl BASE: OH- producer e.g. NaOH Brønsted - Lowry: H+ + A- HA ACID: proton donor (H+) e.g. HCl BASE: proton acceptor e.g. NH3

HA(aq) + H2O(l) H3O+(aq) + A-(aq) Acids, Bases & Equilibrium HA(aq) + H2O(l) H3O+(aq) + A-(aq) A STRONG acid has equilibrium to the right (HA completely ionised) A WEAK acid has equilibrium to the left (HA partly/mostly intact) Equilibrium Equation: Ka is the ACID DISSOCIATION CONSTANT

Conjugate Acid-Base Pairs NH4+ is the conjugate acid of NH3 NH3 is the conjugate base of NH4+ A conjugate base has one less proton than its conjugate acid HSO4–: conjugate base is SO42– conjugate acid is H2SO4 H2SO4 is a dibasic or diprotic acid: H2SO4(aq) + H2O(l) H3O+(aq) + HSO4–(aq) HSO4–(aq) + H2O(l) H3O+(aq) + SO42–(aq)

Acid-Base Reactions ACID + BASE BASE + ACID HF(aq) + H2O(l) conjugate pair ACID + BASE BASE + ACID conjugate pair HF(aq) + H2O(l) HCOOH(aq) + CN-(aq) H2PO4-(aq) + OH-(aq) NH4+(aq) + CO32-(aq) F-(aq) + H3O+(aq) HCOO-(aq) + HCN(aq) HPO42-(aq) + H2O(l) NH3(aq) + HCO3-(aq)

Autoionisation of Water 2 H2O(l) H3O+(aq) + OH–(aq) Equilibrium constant given special symbol: Kw = [H3O+][OH– ] NB: [H2O(l)] = constant At 25 °C: Kw = 1.0  10-14 Neutral solution: [H+] = [OH– ] = 1.0  10-7 M Acidic solution: [H+] > 1.0  10-7 M Basic: [H+] < 1.0  10-7 M remember this

pH = -log10[H+] pOH = -log10[OH-] pH + pOH = 14 The pH Scale Because the concentrations of acids and bases can vary over many orders of magnitude, it is convenient to define a logarithmic scale to compare them: pH = -log10[H+] pOH = -log10[OH-] pH + pOH = 14 e.g. If [H+] = 1.0 x 10-6 M then pH = -log(10-6) = - (-6) = 6.00 Hence, pOH = 14.00 – 6.00 = 8.00 and [OH-] = 10-8.00

The ‘p’ Convention pH = – log10[H+] pOH = – log10[OH– ] pKw = – log10Kw = 14.00 at 25 °C Acid : pH < 7 Neutral: pH = 7 Basic: pH > 7 Since Kw = [H+][OH– ]: log10 Kw = log10 [H+] + log10 [OH– ] – log10 [H+] – log10 [OH– ] = – log10 Kw pH + pOH = 14 pOH = 14 – pH

Temperature Dependence of pH H2O H+ + OH- ΔH0 = 56 kJ mol-1 Ea Kw = 1.0  10-14 only at 25 °C Reaction is endothermic: it is more favourable at higher temperature For T > 25 °C, Kw > 10-14 For T < 25 °C, Kw < 10-14  pH + pOH  14 if T  25 °C  neutral pH  7 if T  25 °C !

} [H+] ACIDIC NEUTRAL BASIC pH 1 M NaOH Household Ammonia Sea Water 10-14 10-12 10-10 10-8 10-6 10-4 10-2 100 ACIDIC NEUTRAL BASIC pH 14 12 10 8 6 4 2 1 M NaOH Household Ammonia Sea Water } Blood Pure Water Milk Vinegar Lemon Juice Stomach Acid 1 M HCl

Practice Examples 1. Calculate the pH for solutions with each of the [H+(aq)] concentrations below (a) 10.0 M (b) 1.00 M (c) 0.10 M (d) 0.010 M 2. Calculate the pH for solutions with each of the [OH-(aq)] concentrations below

Summary: Acids & Bases 1 List common acids and bases Learning Outcomes - you should now be able to: Complete the worksheet List common acids and bases Define acids & bases Use pH and Kw Answer Review Problems 11.1-11.11 and 11.128 in Blackman Next lecture: Calculations involving acids and bases