Acids and Bases

pH scale ACIDBASE NEUTRAL Each step on pH scale represents a factor of 10. pH 5 vs. pH 6 (10X more acidic) pH 3 vs. pH 5 (100X different) pH 8 vs. pH 13 (100,000X different) : measures acidity/basicity 10x 100x

pH scale ACIDBASE NEUTRAL Each step on pH scale represents a factor of 10. pH 5 vs. pH 6 (10X more acidic) pH 3 vs. pH 5 (100X different) : measures acidity/basicity 10x 100x Søren Sorensen ( )

Acid vs. Base Acid pH > 7 bitter taste does not react with metals pH < 7 sour taste react with metals Alike Different Related to H + (proton) concentration pH + pOH = 14 Affects pH and litmus paper Base Different Topic

Properties electrolytes turn litmus red sour taste react with metals to form H 2 gas slippery feel turn litmus blue bitter taste ChemASAP vinegar, milk, soda, apples, citrus fruits ammonia, lye, antacid, baking soda electrolytes

Copyright © 2007 Pearson Benjamin Cummings. All rights reserved. Acid Sour taste Turns blue litmus red Reacts with some metals to produce H 2 Dissolves carbonate salts, releasing CO 2 Base Bitter taste Turns red litmus blue Slippery to the touch

Common Acids and Bases Strong Acids (strong electrolytes) HClhydrochloric acid HNO 3 nitric acid HClO 4 perchloric acid H 2 SO 4 sulfuric acid Weak Acids (weak electrolytes) CH 3 COOHacetic acid H 2 CO 3 carbonic Strong Bases (strong electrolytes) NaOH sodium hydroxide KOH potassium hydroxide Ca(OH) 2 calcium hydroxide Weak Base (weak electrolyte) NH 3 ammonia Kotz, Purcell, Chemistry & Chemical Reactivity 1991, page 145 NH 4 OH ammonia NH 3 + H 2 O  NH 4 OH

Salt Acid + Base  Salt + Water HCl + NaOH  NaCl + HOH salt water

Neutralization Neutralization Neutralization is a chemical reaction between an acid and a base to produce a salt (an ionic compound) and water. NaOH(aq) + HCl(aq) NaCl(aq) + H 2 O(l) baseacidsaltwater Some neutralization reactions: H 2 SO 4 (aq) + NaOH(aq) Na 2 SO 4 +HOH sulfuric acidsodium hydroxidesodium sulfatewater HC 2 H 3 O 2 (aq) + Ca(OH) 2 (aq) Ca(C 2 H 3 O 2 ) 2 +HOH acetic acidcalcium hydroxidecalcium acetatewater

Acid-Base Neutralization Hydronium ion Hydroxide ion H3O+H3O+ OH - Water H2OH2O H2OH2O H2OH2O H2OH2O Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584

Acid-Base Neutralization Hydronium ion Hydroxide ionWater H3O+H3O+ OH - H2OH2O Water H2OH2O Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 584

Acid Precipitation

Formation of Sulfuric Acid Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 302 SO 2 (g) + H 2 O(l) H 2 SO 3 (aq) 2SO 2 (g) + O 2 (g) 2SO 3 (g) SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) SO 2 (g) + H 2 O 2 (l) H 2 SO 4 (aq) Catalyzed by atmospheric dust Sulfuric acid + +

Figure courtesy of the National Atmospheric Deposition Program, Champaign, Ill. The progressively darker red areas on the map indicate the lowest pH levels and areas most prone to problems from acid rain. Hydrogen ion concentration as pH from measurements made at the field laboratories during 2003 National Atmospheric Deposition Program/National Trends Network made at the Central Analytical Laboratory, 1999

Acid Rain Smoke stacks pollute SO 2 into the atmosphere. This combines with water to form acid rain. Estimated sulfate ion deposition, 1999

CO 2 (g) H 2 O (l) H 2 CO 3 (aq) Carbon dioxide Carbonic acid Water Weak acid Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Common Acids Sulfuric AcidH 2 SO 4 Nitric AcidHNO 3 Phosphoric AcidH 3 PO 4 Hydrochloric AcidHCl Acetic Acid CH 3 COOH Carbonic Acid H 2 CO 3 Battery acid Used to make fertilizers and explosives Food flavoring Stomach acid Vinegar Carbonated water

Common Acids Formula FormulaName of AcidName of Negative Ion of Salt HFhydrofluoricfluoride HBrhydrobromicbromide HIhydroiodiciodide HClhydrochloricchloride HClOhypochloroushypochlorite HClO 2 chlorouschlorite HClO 3 chloricchlorate HClO 4 perchloricperchlorate H 2 Shydrosulfuricsulfide H 2 SO 3 sulfuroussulfite H 2 SO 4 sulfuricsulfate HNO 2 nitrousnitrite HNO 3 nitricnitrate H 2 CO 3 carboniccarbonate H 3 PO 3 phosphorousphosphite H 3 PO 4 phosphoricphosphate

Formation of Hydronium Ions 1+ hydronium ion H3O+H3O+ + hydrogen ion H+H+ water H2OH2O 1+ (a proton) 1+

Sulfuric Acid, H 2 SO 4 Sulfuric acid is the most commonly produced industrial chemical in the world. Uses: petroleum refining, metallurgy, manufacture of fertilizer, many industrial processes: metals, paper, paint, dyes, detergents Sulfuric acid is used in automobile batteries. H 2 SO 4 “oil of vitriol”

Nitric Acid, HNO 3 Nitric acid stains proteins yellow (like your skin). Uses: make explosives, fertilizers, rubber, plastics, dyes, and pharmaceuticals. HNO 3 “aqua fortis” O O O N H

Hydrochloric Acid, HCl The stomach produces HCl to aid in the digestion of food. Uses: For ‘pickling’ iron and steel. Pickling is the immersion of metals in acid solution to remove surface impurities. A dilute solution of HCl is called muriatic acid (available in many hardware stores). Muriatic acid is commonly used to adjust pH in swimming pools and in the cleaning of masonry. HCl(g) + H 2 O(l) HCl(aq) hydrogen chloride water hydrochloric acid

Common Bases Sodium hydroxideNaOHlye or caustic soda Potassium hydroxideKOHlye or caustic potash Magnesium hydroxideMg(OH) 2 milk of magnesia Calcium hydroxideCa(OH) 2 slaked lime Ammonia waterNH 3 H 2 Ohousehold ammonia Name Formula Common Name. NH 4 OH NH OH 1- ammonium hydroxide hydroxide ion OH 1-

Relative Strengths of Acids and Bases perchloricHClO 4 hydrogen chlorideHCl nitricHNO 3 sulfuricH 2 SO 4 hydronium ionH 3 O + hydrogen sulfate ionHSO 4 - phosphoricH 3 PO 4 aceticHC 2 H 3 O 2 carbonicH 2 CO 3 hydrogen sulfideH 2 S ammonium ionNH 4 + hydrogen carbonate ionHCO 3 - waterH 2 O ammoniaNH 3 hydrogenH 2 Decreasing Acid Strength perchlorate ionClO 4 - chloride ionCl - nitrate ionNO 3 - hydrogen sulfate ionHSO 4 - waterH 2 O sulfate ionSO 4 2- dihydrogen phosphate ionH 2 PO 4 - acetate ionC 2 H 3 O 2 - hydrogen carbonate ionHCO 3 - hydro sulfide ionHS - ammoniaNH 3 carbonate ionCO 3 2- hydroxide ionOH - amide ionNH 2 - hydride ionH - Decreasing Base Strength Acid Formula Conjugate baseFormula Metcalfe, Williams, Catska, Modern Chemistry  1966, page 229 acid conjugate base + H +

Binary Hydrogen Compounds of Nonmetals When Dissolved in Water (These compounds are commonly called acids.) The prefix hydro- is used to represent hydrogen, followed by the name of the nonmetal with its ending replaced by the suffix –ic and the word acid added. Examples: *HCl HBr *The name of this compound would be hydrogen chloride if it was NOT dissolved in water. Hydrochloric acid Hydrobromic acid

Naming Ternary Compounds from Oxyacids The following table lists the most common families of oxy acids. one more oxygen atom most “common” one less oxygen two less oxygen HClO 4 perchloric acid HClO 3 chloric acid HClO 2 chlorous acid HClO hypochlorous acid H 2 SO 4 sulfuric acid H 2 SO 3 sulfurous acid H 3 PO 4 phosphoric acid H 3 PO 3 phosphorous acid H 3 PO 2 hypophosphorous acid HNO 3 nitric acid HNO 2 nitrous acid (HNO) 2 hyponitrous acid

An acid with a name ending in A salt with a name ending in -ic -ous -ate -ite forms Hill, Petrucci, General Chemistry An Integrated Approach  1999, page 60

Oxyacids  Oxysalts If you replace hydrogen with a metal, you have formed an oxysalt. A salt is a compound consisting of a metal and a non-metal. If the salt consists of a metal, a nonmetal, and oxygen it is called an oxysalt. NaClO 4, sodium perchlorate, is an oxysalt. HClO 4 perchloric acid HClO 3 chloric acid HClO 2 chlorous acid HClO hypochlorous acid NaClO 4 sodium perchlorate NaClO 3 sodium chlorate NaClO 2 sodium chlorite NaClO sodium hypochlorite OXYACID OXYSALT

ACID SALT per stem ic changes to per stem ate stem ic changes to stem ate stem ous changes to stem ite hyper stem ous changes to hypo stem ite HClO 3 + Na 1+ NaClO 3 + H 1+ acid cation salt

Arrhenius Acids and Bases Acids release hydrogen ions in water. Bases release hydroxide ions in water. An acid is a substance that produces hydronium ions, H 3 O +, when dissolved in water. Lewis Definitions A Lewis acid is a substance than can accept (and share) an electron pair. A Lewis base is a substance than can donate (and share) an electron pair. Lewis Acid Brønsted-Lowry Definitions A Brønsted-Lowry acid is a proton donor; it donates a hydrogen ion, H +. A Brønsted-Lowry base is a proton acceptor; it accepts a hydrogen ion, H +. Brønsted-Lowry Arrhenius acids Acid Definitions

Acid – Base Systems TypeAcidBase ArrheniusH + or H 3 O + producer OH - producer Brønsted- Lowry Proton (H + ) donor Proton (H + ) acceptor LewisElectron-pair acceptor Electron-pair donor

Arrhenius Acid hydronium ion H3O+H3O+ 1- chloride ion Cl - water H2OH2O hydrogen chloride HCl (an Arrhenius acid) Any substance that releases H + ions as the only positive ion in the aqueous solution.

Definitions Arrhenius - In aqueous solution…Arrhenius - In aqueous solution… HCl + H 2 O  H 3 O + + Cl – AcidsAcids form hydronium ions (H 3 O + ) H HHHH H Cl OO – + acid Courtesy Christy Johannesson

Definitions Arrhenius - In aqueous solution…Arrhenius - In aqueous solution… BasesBases form hydroxide ions (OH - ) NH 3 + H 2 O  NH OH - H H H H H H N NO O – + H H H H base Courtesy Christy Johannesson

Brønsted-Lowry Acids and Bases 1+ + hydronium ion H3O+H3O+ 1- chloride ion Cl - (base) H2OH2O (acid) HCl ++ -- Acid = any substance that donates a proton. Base = any substance that accepts a proton.

Brønsted-Lowry Acids and Bases 1+ + hydronium ion H3O+H3O+ 1- chloride ion Cl - (base) H2OH2O (acid) HCl ++ -- Acid = any substance that donates a proton. Base = any substance that accepts a proton.

Definitions Brønsted-LowryBrønsted-Lowry HCl + H 2 O  Cl – + H 3 O + AcidsAcids are proton (H + ) donors. BasesBases are proton (H + ) acceptors. conjugate acid conjugate base baseacid Courtesy Christy Johannesson

Definitions F - H 2 PO 4 - H2OH2O HF H 3 PO 4 H 3 O +  Give the conjugate base for each of the following: - an acid with more than one H +  Polyprotic - an acid with more than one H + Courtesy Christy Johannesson

pH of Common Substances Timberlake, Chemistry 7 th Edition, page M HCl 0 gastric juice 1.6 vinegar 2.8 carbonated beverage 3.0 orange 3.5 apple juice 3.8 tomato 4.2 lemon juice 2.2 coffee 5.0 bread 5.5 soil 5.5 potato 5.8 urine 6.0 milk 6.4 water (pure) 7.0 drinking water 7.2 blood 7.4 detergents bile 8.0 seawater 8.5 milk of magnesia 10.5 ammonia 11.0 bleach M NaOH (lye) acidic neutral basic [H + ] = [OH - ]

pH of Common Substance 14 1 x x x x x x x x x x x x x x x x x x x x x x x x x x x x NaOH, 0.1 M Household bleach Household ammonia Lime water Milk of magnesia Borax Baking soda Egg white, seawater Human blood, tears Milk Saliva Rain Black coffee Banana Tomatoes Wine Cola, vinegar Lemon juice Gastric juice More basic More acidic pH [H 1+ ] [OH 1- ] pOH 7 1 x x

pH Calculations pH pOH [H 3 O + ] [OH - ] pH + pOH = 14 pH = -log[H 3 O + ] [H 3 O + ] = 10 -pH pOH = -log[OH - ] [OH - ] = 10 -pOH [H 3 O + ] [OH - ] = 1 x10 -14

pH = - log [H + ] pH = 4.6 pH = - log [H + ] 4.6 = - log [H + ] = log [H + ] Given: 2 nd log 10 x antilog multiply both sides by -1 substitute pH value in equation take antilog of both sides determine the [hydronium ion] choose proper equation [H + ] = 2.51x10 -5 M You can check your answer by working backwards. pH = - log [H + ] pH = - log [2.51x10 -5 M] pH = 4.6 Recall, [H + ] = [H 3 O + ]

Acid Dissociation monoprotic diprotic polyprotic HA(aq) H 1+ (aq) + A 1- (aq) 0.03 M pH = - log [H + ] pH = - log [0.03M] pH = 1.52 e.g. HCl, HNO 3 H 2 A(aq) 2 H 1+ (aq) + A 2- (aq) 0.3 M0.6 M0.3 M pH = - log [H + ] pH = - log [0.6M] pH = 0.22 e.g. H 2 SO 4 Given: pH = 2.1 find [H 3 PO 4 ] assume 100% dissociation e.g. H 3 PO 4 H 3 PO 4 (aq) 3 H 1+ (aq) + PO 4 3- (aq) ? Mx M pH = ?

Given: pH = 2.1 find [H 3 PO 4 ] assume 100% dissociation H 3 PO 4 (aq) 3 H 1+ (aq) + PO 4 3- (aq) X MX M M Step 1) Write the dissociation of phosphoric acid Step 2) Calculate the [H + ] concentration pH = - log [H + ] 2.1 = - log [H + ] = log [H + ] 2 nd log = log [H + ] 2 nd log [H + ] = 10 -pH [H + ] = [H + ] = M [H + ] = 7.94 x10 -3 M 7.94 x10 -3 M Step 3) Calculate [H 3 PO 4 ] concentration Note: coefficients (1:3) for (H 3 PO 4 : H + ) 7.94 x10 -3 M 3 = M H 3 PO 4

How many grams of magnesium hydroxide are needed to add to 500 mL of H 2 O to yield a pH of 10.0? Step 1) Write out the dissociation of magnesium hydroxide Mg 2+ OH 1- Mg(OH) 2 Mg(OH) 2 (aq)Mg 2+ (aq) 2 OH 1- (aq)+ Step 2) Calculate the pOH pH + pOH = pOH = 14 pOH = 4.0 Step 3) Calculate the [OH 1- ] pOH = - log [OH 1- ] [OH 1- ] = 10 -OH [OH 1- ] = 1 x10 -4 M 1 x10 -4 M0.5 x10 -4 M5 x10 -5 M Step 4) Solve for moles of Mg(OH) 2 x = 2.5 x mol Mg(OH) 2 Step 5) Solve for grams of Mg(OH) 2 x g Mg(OH) 2 = 2.5 x mol Mg(OH) 2 1 mol Mg(OH) 2 = g Mg(OH) 2 58 g Mg(OH) 2

pH Indicators

pH Paper pH pH

Indicator Colors in Titration

Red Cabbage Indicator Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Titration Author: J.A.Freyre

23 24 How to read a buret volume mL (not mL) mL?

Titration TitrationTitration –Analytical method in which a standard solution is used to determine the concentration of an unknown solution. standard solution unknown solution Courtesy Christy Johannesson

Equivalence point (endpoint)Equivalence point (endpoint) –Point at which equal amounts of H 3 O + and OH - have been added. –Determined by… indicator color change Titration dramatic change in pH Courtesy Christy Johannesson