Unit 3 Acids and Bases

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

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”

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

Naming Bases Bases are ionic compound. They follow the rules for naming ionic compounds and you have to use criss cross method to write the chemical formula. (The “+” ion first followed by the “-” ion.) Ex. 1 sodium hydroxide Na + OH - NaOH

Naming Bases Ex. 2 KOH K+K+ OH - Potassium hydroxide

Naming Acids and writing formulas for acids Acids donate hydrogen ions (H + ) and their chemical formulas have a hydrogen written at the beginning. Names of acid depend on the negative ion and its ending.

Naming Acids and writing formulas for acids (continued) Anion ends with –ide : Ex. 1 acid formed with anion bromide if anion ends with –ide: To write name use prefix hydro + root of anion+ change –ide ending to –ic + word “acid” NAME: hydrobromic acid

Naming Acids and writing formulas for acids (continued) Anion ends with –ate : Ex. 2 acid formed with anion carbonate if anion ends with –ate: To write name Use root of anion+ change –ate ending to –ic + word “acid” NAME: carbonic acid

Naming Acids and writing formulas for acids (continued) Anion ends with –ite : Ex. 3 acid formed with anion nitrite if anion ends with –ite: To write name Use root of anion+ change –ite ending to –ous + word “acid” NAME: nitrous acid

Naming Acids and writing formulas for acids (continued) All acids have as the positive ion the hydrogen ion (H+) and a negative ion that can be identified by the name of the acid. Ex. 4 hydrochloric acid if name of ion includes prefix hydro and has an -ic ending, then the anion has an -ide ending. From ion sheet determine which ion has root like the anion and an -ide ending. For the example is the chloride ion which formula is Cl - H+H+ Cl - HCl

Naming Acids and writing formulas for acids (continued) Ex. 4 phosphoric acid if name of ion has an -ic ending, then the anion has an -ate ending. From ion sheet determine which ion has root like the anion and an -ate ending. For the example is the phosphate ion which formula is PO 4 3- H+H+ PO 4 3- H 3 PO 4

Naming Acids and writing formulas for acids (continued) Ex. 4 phosphorous acid if name of ion has an -ous ending, then the anion has an - ite ending. From ion sheet determine which ion has root like the anion and an -ite ending. For the example is the phosphite ion which formula is PO 3 3- H+H+ PO 3 3- H 3 PO 3

Acids properties 1. Conduct electricity (strong acids) 2. Change blue litmus to red 3. Have a sour taste 4. React with bases to neutralize their properties 5. React with active metals to liberate hydrogen 6. pH values <7

Acids Acids are defined as: Substances which ionize to form hydrogen ions (H + ) in aqueous solution. (Arrhenius) Substances that act as proton donors, H + (Bronsted- Lowry) or as electron-pair acceptors (Lewis) Examples HCl, H 2 SO 4

Bases properties Base properties 1. Conduct electricity (strong bases) 2. Change red litmus to blue 3. Have a slippery feeling (like soap) 4. React with acids to neutralize their properties 5. pH values >7

Bases Bases are defined as: Substances which ionize to form hydroxide ions OH(-) in aqueous solution Substances that act as proton receptors (Bronsted-Lowry) or as electron-pair donors (Lewis) Examples: NH 3 OH, NaOH, CaCO 3, NaHCO 3 (baking soda) AMMONIA cleaner

pH Scale The pH scale is used to measure how acidic or basic a liquid is. pH measures the concentration of hydrogen ions (H+) and hydroxide ions (OH-). The scale goes from 0 through 14. Distilled water is 7, so is called neutral. lemon juice pH Acidic Neutral Basic vinegar d water baking soda ammonia detergent

Indicators IndicatorAcidBase Red litmus paperStays sameTurns blue Blue litmus paperTurns redStays same Bromophenol blueYellowStays blue PhenolphtaleinColorlessPink An indicator is a large organic molecule that works somewhat like a "color dye."

Natural indicators There are natural indicators for acids and bases, and we may find them in our kitchen or garden! Red rose flowers Bougainvillea flowers Red cabbage Blue berries

Practice: identifying acid and bases 1) HCl + H2O  H3O + + Cl – HCl is the acid because it is donating a H + to H 2 O H 2 O is the base because it is accepting a H + from HCl Cl - is the conjugate base because it’s what’s left after the acid donates a H + H+H+ H 3 O + is the conjugate acid because it’s what’s left after the base accepts a H +

Practice: identifying acid and bases 2) CN - + H2O  OH - + HCN H 2 O is the acid because it is donating a H + to CN - CN - is the base because it is accepting a H + from H 2 O OH - is the conjugate base because it’s what’s left after the acid donates a H + H+H+ HCN is the conjugate acid because it’s what’s left after the base accepts a H +

Practice: identifying acid and bases 3) OH - + HI  H+H+ The acid can donate a H + and its chemical formula has a H at the beginning acid Donates a H + H2OH2O+ I-I- Classwork :handout conjugate acids and bases

Common Acids Strong Acids stomach acid; (dissociate ~100%) pickling: cleaning metals w /conc. HCl sulfuric acid: H 2 SO 4 2 H 1+ + SO 4 2– -- #1 chemical;(auto) battery acid explosives; nitric acid: HNO 3 H 1+ + NO 3 1– -- fertilizer

Common Acids (cont.) Weak Acids (dissociate very little) acetic acid: CH 3 COOH H 1+ + CH 3 COO 1– -- hydrofluoric acid: HF H 1+ + F 1– -- citric acid, H 3 C 6 H 5 O 7 -- ascorbic acid, H 2 C 6 H 6 O 6 -- lactic acid, CH 3 CHOHCOOH -- vinegar; naturally made by apples used to etch glass lemons or limes; sour candy vitamin C waste product of muscular exertion

carbonic acid, H 2 CO 3 -- carbonated beverages -- CO 2 + H 2 O H 2 CO 3 dissolves limestone (CaCO 3 ) rainwater in air H 2 CO 3 : cave formation H 2 CO 3 : natural acidity of lakes H 2 CO 3 : beverage carbonation

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

pH Scale Acid Base Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 515 [H + ] pH M NaOH Ammonia (household cleaner) Blood Pure water Milk Vinegar Lemon juice Stomach acid 1 M HCl Acidic Neutral Basic

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 - ]

Acid – Base Concentrations pH = 3 pH = 7 pH = 11 OH - H3O+H3O+ H3O+H3O+ H3O+H3O+ [H 3 O + ] = [OH - ] [H 3 O + ] > [OH - ] [H 3 O + ] < [OH - ] acidic solution neutral solution basic solution concentration (moles/L) Timberlake, Chemistry 7 th Edition, page 332

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

[ ] are used to represent concentration, usually molarity (mol/L) or (mol/dm 3 ). pH has no units.

Example 1 What is the pH of a solution that contains 1.00x10 -4 mol H 3 O + /dm 3 ? Given [ H 3 O + ]= 1.00x10 -4 mol H 3 O + /dm 3 Unknown: pH pH = -log[H 3 O + ] pH = -log[1.00x10 -4 ] pH = 4.00

Example 2 What is the pH and pOH of a solution that contains mol H 3 O + /dm 3 ? Given [ H 3 O + ]= mol H 3 O + /dm 3 Unknown: pH and pOH pH = -log[H 3 O + ] pH = -log[ ] pH = 2.46 pH + pOH = 14 pOH = 14 – pH= = 11.54

Example 3 What is the [H 3 O + ] and [OH - ] of a solution if pOH=4.40 Given: pOH= 4.40 Unknown: [H 3 O + ] and [OH - ] [OH - ] = 10 -pOH [OH - ] = [OH - ] = 3.98x10 -5 M [H 3 O + ] [OH - ] = 1 x [H 3 O + ] = 1 x = 1 x = 2.51x M [OH - ] 3.98x10 -5

classwork P 184 #15,16,17

Strengths of acids and bases Strong acids and bases : ionize completely in aqueous solution. HCl (g) + H 2 O (l)  H 3 O + (aq) + Cl - (aq) (100% ionized) Examples: HCl, HNO 3, H 2 SO 4, KOH, NaOH Weak acids and bases: ionize slightly in aqueous solution. CH 3 COOH (aq) + H 2 O (l) H 3 O + (aq) + CH 3 COOH - (aq) (partially ionized) Examples: HClO, H 3 PO 4, NH 3

Reactions between acids and bases When and acid and a base react with each other it is called neutralization reaction.

Reactions between acids and bases General formula for acid base reaction: Acid+Base→ H2OH2O+ Salt “Salt” means any ionic compound formed from an acid/base reaction NOT JUST NaCl !!

Acids and bases reactions The acids react with bases, forming salts ACID + BASE → SALT + WATER HOH HCl + NaOH → NaCl + H 2 O H-OH

Titration Equivalence point: when number of moles of hydrogen ions equals the number of moles of hydroxide ions. Titration: adding a known amount of a solution of known concentration to determine the concentration of another solution. Standard solution: solution of known concentration End point: point at which the indicator changes color Point of neutralization is the end point of the titration.

Ex. 1 How many milliliters of 0.45M HCl will neutralize 25.0 mL of 1.00M KOH? mL HCl= 25.0mL x 1.00M KOH 0.45 M HCl mL HCl= 55.6mL HCl

Ex. 2 What is the molarity of a NaOH solution if 20.0 mL of the solution is neutralized by 28.0mL of 1.00 M HCl? M NaOH= 1.00 M HCl x 28.0 mL 20.0 mL M NaOH = 1.40 M Classwork: p 189 # 23 (a,c,d), 25, 26