Bài giảng Chapter 15 Acids and Bases

Chapter 15 Acids and Bases 2011, NKMB Co., Ltd. Chemistry, Julia Burdge, 2 st Ed. McGraw Hill. Mr. Truong Minh Chien ; losedtales@yahoo.com http://tailieu.vn/losedtales http://mba-programming.blogspot.com 2 Stomach Acid & Heartburn • the cells that line your stomach produce hydrochloric acid  to kill unwanted bacteria  to help break down food  to activate enzymes that break down food • if the stomach acid backs up into your esophagus, it irritates those tissues, resulting in heartburn  acid reflux  GERD = gastroesophageal reflux disease = chronic leaking of stomach acid into the esophagus Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 3 Curing Heartburn • mild cases of heartburn can be cured by neutralizing the acid in the esophagus  swallowing saliva which contains bicarbonate ion  taking antacids that contain hydroxide ions and/or carbonate ions Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 5 Common Acids Chemical Name Formula Uses Strength Nitric Acid HNO 3 explosive, fertilizer, dye, glue Strong Sulfuric Acid H 2 SO 4 explosive, fertilizer, dye, glue, batteries Strong Hydrochloric Acid HCl metal cleaning, food prep, ore refining, stomach acid Strong Phosphoric Acid H 3 PO 4 fertilizer, plastics & rubber, food preservation Moderate Acetic Acid HC 2 H 3 O 2 plastics & rubber, food preservation, Vinegar Weak Hydrofluoric Acid HF metal cleaning, glass etching Weak Carbonic Acid H 2 CO 3 soda water Weak Boric Acid H 3 BO 3 eye wash Weak Chemistry, Julia Burdge, 2 nd e., McGraw Hill. Tro, Chemistry: A Molecular Approach 7 Structure of Acids • oxy acids have acid hydrogens attached to an oxygen atom  H 2 SO 4 , HNO 3 Tro, Chemistry: A Molecular Approach 8 Structure of Acids • carboxylic acids have COOH group  HC 2 H 3 O 2 , H 3 C 6 H 5 O 7 • only the first H in the formula is acidic  the H is on the COOH Tro, Chemistry: A Molecular Approach 9 Properties of Bases • also known as alkalis • taste bitter  alkaloids = plant product that is alkaline  often poisonous • solutions feel slippery • change color of vegetable dyes  different color than acid  red litmus turns blue • react with acids to form ionic salts  neutralization Tro, Chemistry: A Molecular Approach 10 Common Bases Chemical Name Formula Common Name Uses Strength sodium hydroxide NaOH lye, caustic soda soap, plastic, petrol refining Strong potassium hydroxide KOH caustic potash soap, cotton, electroplating Strong calcium hydroxide Ca(OH) 2 slaked lime cement Strong sodium bicarbonate NaHCO 3 baking soda cooking, antacid Weak magnesium hydroxide Mg(OH) 2 milk of magnesia antacid Weak ammonium hydroxide NH 4 OH, {NH 3 (aq)} ammonia water detergent, fertilizer, explosives, fibers Weak Tro, Chemistry: A Molecular Approach 13 Arrhenius Theory • bases dissociate in water to produce OH - ions and cations  ionic substances dissociate in water NaOH(aq) → Na + (aq) + OH – (aq) • acids ionize in water to produce H + ions and anions  because molecular acids are not made of ions, they cannot dissociate  they must be pulled apart, or ionized, by the water HCl(aq) → H + (aq) + Cl – (aq)  in formula, ionizable H written in front HC 2 H 3 O 2 (aq) → H + (aq) + C 2 H 3 O 2 – (aq) Tro, Chemistry: A Molecular Approach 14 Arrhenius Theory HCl ionizes in water, producing H + and Cl – ions NaOH dissociates in water, producing Na + and OH – ions [...]... Brønsted-Lowry Acids and Bases and Their Conjugates in the Reaction H2SO4 + H2O ⇔ HSO4– + H3O+ When the H2SO4 becomes HSO4−, it lost an H+ − so H2SO4 must be the acid and HSO4− its conjugate base When the H2O becomes H3O+, it accepted an H+ − so H2O must be the base and H3O+ its conjugate acid H2SO4 + acid H2O base Tro, Chemistry: A Molecular Approach ⇔ HSO4– conjugate base + H3O+ conjugate acid 26 Ex 15. 1b – Identify... conjugate base + H3O+ conjugate acid 26 Ex 15. 1b – Identify the Brønsted-Lowry Acids and Bases and Their Conjugates in the Reaction HCO3– + H2O ⇔ H2CO3 + HO– When the HCO3− becomes H2CO3, it accepted an H+ − so HCO3− must be the base and H2CO3 its conjugate acid When the H2O becomes OH−, it donated an H+ − so H2O must be the acid and OH− its conjugate base HCO3– + base H2O acid Tro, Chemistry: A Molecular... Tro, Chemistry: A Molecular Approach 33 Strong Acids • The stronger the acid, the more willing it is to donate H  use water as the standard base HCl → H+ + ClHCl + H2O→ H3O+ + Cl- • strong acids donate practically all their H’s  100% ionized in water  strong electrolyte • [H3O+] = [strong acid] Tro, Chemistry: A Molecular Approach 34 Weak Acids • weak acids donate a small fraction of their H’s most... acid; and the original acid becomes the conjugate base Tro, Chemistry: A Molecular Approach 23 Brønsted-Lowry Acid-Base Reactions :B base ⇔ HCHO2 + H2O acid base ⇔ H2O + acid ⇔ H–A acid + NH3 base Tro, Chemistry: A Molecular Approach :A– + conjugate base CHO2– conjugate base H–B+ conjugate acid + H3O+ conjugate acid HO– conjugate base + NH4+ conjugate acid 24 Ex 15. 1a – Identify the Brønsted-Lowry Acids. .. reverse process • and the original acid has a lone pair of electrons after the reaction – so it will act as a base in the reverse process :A– + H–B+ ⇔ H–A + :B Tro, Chemistry: A Molecular Approach 22 Conjugate Pairs • In a Brønsted-Lowry Acid-Base reaction, the original base becomes an acid in the reverse reaction, and the original acid becomes a base in the reverse process • each reactant and the product... [weak acid] Tro, Chemistry: A Molecular Approach 35 Polyprotic Acids • often acid molecules have more than one ionizable H – these are called polyprotic acids  the ionizable H’s may have different acid strengths or be equal  1 H = monoprotic, 2 H = diprotic, 3 H = triprotic  HCl = monoprotic, H2SO4 = diprotic, H3PO4 = triprotic • polyprotic acids ionize in steps  each ionizable H removed sequentially... with an unshared pair of electrons • in an acid-base reaction, the acid molecule gives an H+ to the base molecule H–A + :B ⇔ :A– + H–B+ Tro, Chemistry: A Molecular Approach 18 Brønsted-Lowry Acids • Brønsted-Lowry acids are H+ donors any material that has H can potentially be a BrønstedLowry acid because of the molecular structure, often one H in the molecule is easier to transfer than others • HCl(aq)... because HCl transfers an H+ to H2O, forming H3O+ ions water acts as base, accepting H+ HCl(aq) + H2O(l) → Cl–(aq) + H3O+(aq) acid base Tro, Chemistry: A Molecular Approach 19 Brønsted-Lowry Bases • Brønsted-Lowry bases are H+ acceptors any material that has atoms with lone pairs can potentially be a Brønsted-Lowry base because of the molecular structure, often one atom in the molecule is more willing... water molecule(s) to produce complex ions, mainly hydronium ion, H3O+ H+ + H2O → H3O+  there are also minor amounts of H+ with multiple water molecules, H(H2O)n+ Tro, Chemistry: A Molecular Approach 15 Arrhenius Acid-Base Reactions • the H+ from the acid combines with the OHfrom the base to make a molecule of H2O it is often helpful to think of H2O as H-OH • the cation from the base combines with... donating H+ NH3(aq) + H2O(l) ⇔ NH4+(aq) + OH–(aq) base acid Tro, Chemistry: A Molecular Approach 20 Amphoteric Substances • amphoteric substances can act as either an acid or a base have both transferable H and atom with lone pair • water acts as base, accepting H+ from HCl HCl(aq) + H2O(l) → Cl–(aq) + H3O+(aq) • water acts as acid, donating H+ to NH3 NH3(aq) + H2O(l) ⇔ NH4+(aq) + OH–(aq) Tro, Chemistry: . Chapter 15 Acids and Bases 2011, NKMB Co., Ltd. Chemistry, Julia Burdge, 2 st Ed. McGraw. bicarbonate ion  taking antacids that contain hydroxide ions and/ or carbonate ions Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 5 Common Acids Chemical Name