Chapter 8 Acids and Bases 산과 염기

Acids What is an Acid? Properties Classes of Acids Common Acids Hydrogen ion, proton (H+) donor Properties Taste sour, reacts with metals, donates protons Classes of Acids Common Acids Two classes of acids – organic acids and inorganic acids Battery acid sulfuric acid Stomach acid hydrochloric acid Lemon juice citric acid, ascorbic acid Vinegar acetic acid Wine tartaric acid

HA(aq) + H2O(l)  H3O+(aq) + A-(aq) Acid Reaction 물과의 반응 HA  H+ + A- H+ + H2O  H3O+ HA(aq) + H2O(l)  H3O+(aq) + A-(aq) Acids increase the hydronium ion concentration in water

Hydronium Ion

Types of Acids Strong Weak Acids that dissociate completely in water Inorganic Acids HCl, H2SO4, HNO3, HClO4 Weak Acids that partially dissociate in water Organic Acids 강산을 제외한 대부분의 산

Bases What is a base? Properties Common Bases Hydrogen ion acceptor Hydroxide ion (OH-) and Ammonia (NH3) Properties Taste bitter, forms insoluble hydroxide with metals, accepts hydrogen ions Common Bases Baking Soda Sodium bicarbonate Lye Sodium hydroxide Quicklime (lime) calcium oxide Ammonia organic base

BOH(aq)  B+(aq) + OH-(aq) Base Reaction Generic Reaction in Water BOH  B+ + OH- OH- + H2O  H2O + OH- BOH(aq)  B+(aq) + OH-(aq) Bases increase the hydroxide ion concentration

Chemical Equilibrium What determines strong vs weak? The state in a reaction when there in no change in the concentration of the reactants or products Reactions that proceed in both directions at the same time (rate)

Carbon Dioxide Carbon Dioxide, CO2 CO2 + H2O  H2CO3 H2CO3 + H2O  H3O+ + HCO3- HCO3- + H2O  H3O+ + CO3-2 H2CO3- + 2 H2O  2 H3O+ + CO3-2

Acid-Base Pairs Acid that loses a H+ becomes a base Called conjugate base H2CO3 + H2O  H3O+ + HCO3- 짝산 - 짝염기

Water H2O + H2O  H3O+ + OH- Auto protolysis Amphiprotic (Amphoteric) substance that can behave as an acid or a base

Water [H+] = 1 x 10-7 mol/L [OH-] = 1 x 10-7 mol/L Kw = [H+] x [OH-] = 1 x 10-14

pH Scale pH = - log [H+] pOH = - log [OH+] pH + pOH = 14 Concentration [H+] or [OH-] pH = - log [H+] pOH = - log [OH+] What is the pH of neutral water? pH + pOH = 14 Acidic pH < 7 Neutral pH = 7 Basic pH > 7

Conversions acidic/neutral /basic pH of common substances Acidic pH < 7 [H+] > 1e-7 Neutral pH = 7 Basic pH > 7 [H+] < 1e-7 Battery acid pH 1.3 Blood pH 7.3-7.5 Lemon juice pH 2.3 Stomach Acid pH 1.5-2.5 Vinegar pH 2.5 Cheese pH 4.8-6.4 Baking soda pH 8.3 Detergents pH 10-11 Drain cleaner pH 13+ Borax pH 9.2

Measuring pH Meters Indicators Common Indicators meter uses a standard electrode to measure the hydrogen ion concentration, [H+] Indicators Molecules that change color depending on the hydrogen ion concentration, [H+] Common Indicators Thymol blue pH range 1.2-2.8 Bromocresol green pH range 4.0-5.6 Phenol red pH range 6.4-8.0 Phenolphthalein pH range 8.0-10.0

Natural Indicators Anthocyanins found in flower, fruits and vegetables + O H + O H Pelargonidin (pink) Cyanindin (violet) Delphinidin (pale blue) + O H

Neutralization 중화 적정, Titration process of adding acid or base to a solution to achieve a neutral solution, pH = 7 equal amounts of acid and base 적정, Titration determination of the concentration of a solution by reaction with a solution of known concentration

Neutralization 당량점 Equivalence Point Mole Acid = Moles of Base the point in a titration when equal portions of the reactants have been added (stoichiometry) Mole Acid = Moles of Base MAVA = MBVB

Buffers 완충용액, Buffers Example chemical systems composed of acid-base pairs that resist changes in pH buffers contain an acid-base pair which maintain the pH Example Acetic Acid and Sodium Acetate

Buffers pH = pKa + log{[base form]/[acid form]}

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