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Acid, Bases, and Salts Chemistry—Part 1 I. Acids H is a nonmetal or polyatomic ion could be Cl- , SO42-, etc. Ex: HCl, HF, H2SO4 , HClO4, H3PO4 Acids (con’t) dissociate to form H+ ions (protons) Hydrogen Atom Hydrogen Ion (proton) e- + A. Ionization in Water HCl + H2O H3O+ + Cl- + - H+ combines with H2O to form H3O+ Hydronium Ion H+(proton) is attracted to lone e- pairs in H2O Try This: H2SO4 + 2H2O 2 H3O+ + SO42- + SO42- SO42- + H3PO4 + 3H2O 3 H3O+ + PO43- B. Examples • Soda pop – H2CO3, H3PO4 • Vinegar (acetic acid) – HC2H3O2 • Lemons – citric acid • Stomach acid – HCl • Battery acid – H2SO4 • Sour Patch Kids – Tartaric Acid C. Properties • taste sour • conduct electricity • turn litmus red • react with some metals to produce H2 (g) Remember, Zn + 2HCl ZnCl2 + H2(g) • corrosive • All form H+ ions in solution II. Bases contain OH- (hydroxide ions) Ex: Ca(OH)2, LiOH, NH4OH, NaOH Also called alkaline (alkali) Alkali Flats Bonneville Salt Flats, Utah A. Ionization In Water H2O NaOH Na+ + OH- H2O NH4OH NH4+ + OH- H2O Ca(OH)2 Ca2+ + 2 OH- B. Examples • Drano – NaOH • Oven cleaner – KOH • Tums – Ca(OH)2 • Glass cleaner – NH4OH C. Properties • Taste bitter (Baking Soda) • Conduct electricity • Turn litmus blue • Feel slippery (hard to wash off of skin) • Caustic (dissolves protein, ie. YOU) • Form OH- ions III. Reactions of Acids and Bases Neutralization: Acid + Base Salt + Water HBr + NaOH NaBr + H2O Type of reaction? DOUBLE DISPLACEMENT! Try This: HF + LiOH HOH + LiF (H2O) H2SO4 + 2 KOH 2 H2O + K2SO4 Antacids Neutralize stomach acid Ex: Tums 2 HCl + Ca(OH)2 2 H2O + CaCl2 Milk of Magnesia (demo) 2 HCl+ Mg(OH)2 2 H2O + MgCl2 IV. Electrolyte Solutions Substances whose water solutions conduct electricity NaCl (c) vs. NaCl (aq) Sucrose (c) vs. Sucrose (aq) H2O (distilled) vs. H2O (tap) There must be ions present to conduct Strong & Weak Electrolytes STRONG ELECTROLYTES Ionize 100% NaCl (s) NaCl Na+ + Cl- Na+ Na+ Cl - Cl - only ions are present WEAK ELECTROLYTES Only partially ionize HF (s) HF H+ + F- HF F+ HF HF H+ mostly HF present; only some ions Conductivity Demo NH4OH + HC2H3O2 H2O + NH4C2H3O2 Weak Weak Salt Base Acid Practice Salt Parent Acid Parent Base H? ?OH LiBr HBr LiOH K2CO3 H2CO3 KOH (NH4)2SO4 H2SO4 NH4OH Lab 49 Pre - Lab NaCl Na+ (aq) + Cl- (aq) FeCl3 Fe3+ (aq) + 3 Cl- (aq) C6H12O6 C6H12O6 (aq) V. Naming Acids, Bases & Salts Acid Names 1. Binary Acids contain only TWO elements ex: HCl Hydrochloric Acid Hydro-stem-ic Acid Try: HBr Hydrobromic Acid HF Hydrofluoric Acid H2S Hydrosulfuric Acid 1. Ternary Acids contain THREE elements (usually) contain H and a polyatomic ion ate ic ite ous ex: H2CO3 carbonate carbonic Carbonic Acid Try These HNO2 nitrite nitrous Nitrous Acid HNO3 nitrate nitric Nitric Acid H2SO3 sulfite sulfurous Sulfurous Acid H2SO4 sulfate sulfuric Sulfuric Acid Base Names (IUPAC Nomenclature) Combine names of ions NaOH Sodium Hydroxide Ca(OH)2 Calcium Hydroxide Salt Names Combine names of ions NaBr Sodium Bromide K2SO4 Potassium Sulfate Cu(NO3)2 Copper (II) Nitrate VI. Salts Salts are ionic and crystalline A. Dissociation in Water H2O Salt Cation + Anion H2O LiCl Li+ + Cl- H2O Na2SO4 2 Na+ + SO42- B. Cation and Anion Cation: Positive (+) charge The ___________ contributes the cation (acid/base?) Anion: Negative (-) charge The ___________ contributes the anion (acid/base?) C. Examples Cation Anion NaCl Na+ Cl- NaHCO3 Na+ HCO3- K2SO4 K+ SO42- Parent Acid / Parent Base Parent Acid: The acid that contributes the ANION to the salt Parent Base: The base that contributes the CATION to the salt VIII. Strong Acids and Bases STRONG ACIDS—DISSOCIATE 100 % HCl HNO3 H2SO4 STRONG BASES—DISSOCIATE 100% All Alkali Metals (IA) form strong bases VIII. Weak Acids and Bases WEAK ACIDS—DO NOT DISSOCIATE 100 % WEAK BASES—DO NOT DISSOCIATE 100% How would a weak acid conduct electricity compared to a strong acid? IX. Polyprotic Acids Acids with more than one proton (H+) A. Examples H2SO4 H3AsO4 H3PO4 H2CO3 H2S B. Step – By – Step Ionization Acids lose one proton at a time 1st H3PO4 H+ + H2PO4- 2nd H2PO4- H+ + HPO4-2 3rd HPO4-2 H+ + PO4-3 H3PO4 3H+ + PO43- H3PO4 + 3 H2O 3 H3O+ + PO43- Questions 1. Which of the following are polyprotic acids? a) HCl d) HC2H3O2 b) NH3 e) H3PO4 c) H2SO4 f) HNO3 2. Which acid is harder to ionize: H3PO4 or HPO4-2? Why? The -2 charge attracts protons (H+) 3. Which acid is stronger: H2SO4 or HSO4-? Why? easier to lose protons (H+) Lab 50 Answers Water as an acid and a base amphoteric: water behaves as an acid & base H 2O + H2O H3O+ + OH- acid base conj conj acid base X. Anhydrides Without water Acidic Anhydrides— non-metallic oxides that combine with H2O to form an acid SO2 + H2O H2SO3 CO2 + H2O H2CO3 Acid Anhydrides Basic Anhydrides— metal oxides that combine with H2O to form a base CaO + H2O Ca(OH)2 Na2O + H2O 2 NaOH Basic Anhydrides Try These: Acidic or Basic Anhydride? K2O Basic Anhydride NO2 Acidic Anhydride • http://www.epa.gov/maia/images/acid.jpg Acid, Bases, and Salts Chemistry—Part 2 I. Molarity Example: 6 M KOH 0.1 M H2SO4 2 M NaCl A measure of concentration # moles M L solution Concentration 6M 1M Examples 3 M HNO3 = 3 moles HNO 3 1 L solution 20 moles in 5 L = ? M 20moles 4M 5L Try This! If 80 grams of NaOH (MW=40) is dissolved in 2 L, find the molarity. 80 g 2moles 2moles 1M 40 g / mol 2L 6 moles of HBr in 250 ml. Molarity? 6moles xmoles x 24M 250ml 1000ml Now Try This One! moles How many moles of M HCl are in 500 ml of L a 3 M solution? xmoles 3M 0. 5 L x 1.5moles II. Titration Using a solution of known concentration to determine the concentration of another solution. A neutralization reaction Acid + Base Salt + Water End Point The point at which neutralization is complete moles H+ = moles OH- use acid-base indicators (like phenolphthalein) to determine the end point Acidic— before neutralization Neutral— ”End Point” Basic— “overshot endpoint” NaOH Na+ + OH- 1M 50 ml 1M HCl H+ + Cl- 50 ml 1M 1M H2SO4 2 H+ + SO42- 25 ml 1M 2M NaOH Na+ + OH- 1M 50 ml 1M HCl H+ + Cl- 25 ml 2M 2M Titration Equation M AVA # H M BVB #OH MA = Molarity of Acid VA = Volume of Acid #H+= Number of H’s in acid formula UNITS MUST MATCH!!! MB = Molarity of Base VB = Volume of Base #OH- = Number of OH’s in base formula Try This 50 ml of 0.1 M NaOH is neutralized by 5 ml of HCl. Find the molarity of the acid. M AVA # H M BVB #OH ( M A )(5ml )(1H ) (0.1M )(50ml )(1OH ) (5ml)(1H +) (5ml)(1H+) M A 1M Try This 40 ml of 1M KOH is neutralized by 10 ml of sulfuric acid. Find the molarity of acid. M AVA # H M BVB #OH ( M A )(10ml )(2 H ) (1M )(40ml )(1OH ) (10ml)(2H +) (10ml)(2H+) M A 2M III. Indicators Weak organic acids or bases that are a different color in an acid than in a base Ex: Phenolpthalein Bromothymol Blue Litmus Red Cabbage Limitations of Indicators Solutions must be colorless Eye must be able to detect the change IV. Ionization of Water [ ] stands for concentration In pure water, [H+] = 10-7 M and [OH-] = 10-7 M 1 water out of 10,000,000 forms ions Kw – water’s ionization constant Kw = [H+] [OH-] Kw = (10-7) (10-7) Kw = 10-14 so… CONSTANT 10-14 = [H+][OH-] Add Acid? Add Base? Example #1 [OH-] = 10-6 M [H+] = ? K w [ H ][ OH ] 14 6 10 [ H ][10 ] 8 [ H ] 10 M Example #2 [H+] = 10-3 M [OH-] = ? K w [ H ][ OH ] 14 3 10 [10 ][ OH ] 11 [OH ] 10 M pH Scale Used to measure acidity Based on the concentration of H+ ions When the [H+] increases by 10, the pH decreases by 1. When the pH increases by 2, the [H+] decreases by102 = 100 _____ pH = -log[H+] [H+] = 10-4 4 pH = ______ acidic or basic? [H+] = 10-11 11 pH = ______ acidic or basic? pOH = -log[OH+] [OH-] = 10-3 3 pOH = ______ [H+] = 10-9 5 pOH = ______ pH + pOH = 14 Why? [H+] [OH-] = 10-14 - log (10-7) (10-7) = 10-14 - log pH + pOH = 14 Try These: For a solution that is 0.1 M HCl… 1) What is the pH? 2) What is the concentration of OH- ions? 3) What is the pOH? For a solution that is 0.001 M NaOH… 1) What is the pOH? 2) What is the pH? 3) What is [H+]? For a solution that has a pH of 8… 1) What is the [H+]? Hydrolysis The reaction of a salt with water to form an acidic or basic solution Recall Strong Acids: HCl HNO3 H2SO4 Recall Strong Bases: Group IA Hydroxides Look at the Parent Acid & Parent Base Salt Parent Acid Parent Base Neutral STRONG STRONG Acidic STRONG weak Basic weak STRONG Ex: NaF Parent Acid: HF strong or weak? Parent Base: NaOH strong or weak? So…NaF is BASIC Try This: Fe(NO3)3 Parent Acid: HNO3 strong or weak? Parent Base: Fe(OH)3 strong or weak? So…Fe(NO3)3 is ACIDIC Try This: NaCl Parent Acid: HCl strong or weak? Parent Base: NaOH strong or weak? So…NaCl is NEUTRAL
"Acid_ Bases_ and Salts"