Acid-Base 2/27/2012. Definitions of Acids/Bases. Acid-Base Behavior. Arrhenius Definition. Arrhenius Definition

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1 Acids Taste sour Burn Skin Turn Litmus Red Dissolve metals Citrus fruit Vitamin C (Ascorbic Acid) Vinegar Battery Acid Bases Taste Bitter Behavior Burn Skin/Feel Slippery Turn Litmus Blue Soap Ammonia Baking Soda Tums Drano A. Arrhenius B. Bronsted/Lowry C. Lewis Definitions of Acids/Bases Arrhenius Definition A. Acids Produce H 3 O (H ) in water B. Bases Produce OH - in water C. Examples HCl H 2 O HNO 3 H 2 O HClO 4 H 2 O HBr H 2 O NaOH KOH Ba(OH) 2 D. H 3 O - hydronium ion Arrhenius Definition 1

2 Arrhenius Definition Bronsted-Lowry Definition A. Acid H (proton) donor B. Base - H (proton) acceptor C. Works even if water is not present D. Examples HCl H 2 O NH 3 H 2 O HC 2 H 3 O 2 H 2 O Bronsted-Lowry Definition OCl - H 2 O Bronsted-Lowry Definition Water and K w NH 3 H 2 PO 4 - NH 4 HPO 4 What is the conjugate base of: HClO 4 H 2 S PH 4 HCO - 3 What is the conjugate acid of: CN - SO 4 H 2 O HCO - 3 E. Amphiprotic acts as either an acid or base (H 2 O) 1. Autoionization of H 2 O 2H 2 O(l) H 3 O (aq) OH - (aq) 2. K w = [H 3 O ][OH - ]/[H 2 O] 2 K w = [H 3 O ][OH - ] K w = 1 X

3 K w and ph 1. K w = [H 3 O ][OH - ] All aqueous solns contain BOTH H 3 O and OH Acidic solns contain more H 3 O (hydronium ion) 3. Basic solns contain more OH - (hydroxide) 4. Neutral solution H 3 O = OH - H 3 O OH - A/B? 2 X X X X X [OH - ] Neutral K w and ph ph ph 1. Measure of acidity/basicity(alkalinity) Acidic 7 Neutral Basic/Alkaline 2. Logarithmic Scale ph = 2 [H 3 O ] = 0.01 M ph = 1 [H 3 O ] = 0.1 M 3. Each change in ph is a factor of 10 (Richter scale is also logarithmic) 4. Indicators ph ph 13 Oven Cleaner/Drano 12 Hair remover 11 Ammonia 10 Soap 9 Baking Soda, bleach, antacids 8 Shampoo 7 Water, blood, eggs, baby shampoo 6 Urine, milk, saliva 5 Coffee, bread, rainwater 4 Tomatoes 3 Vinegar, soda, beer 2 Stomach acid, lemon juice 1 Battery acid 3

4 ph ph 2/27/2012 ph vs. [H 3 O ] ph vs. log[h 3 O ] Series [H3O] log[h3o] ph Formula ph Formula 1. ph = -log [H 3 O ] 2. Examples What is the ph if the [H 3 O ] of a solution is 1 X 10-12? What is the ph if the [H 3 O ] of a solution is 5.0 X 10-6? (5.3) What is the [H 3 O ] of a solution if the ph = 3.76? What is the [H 3 O ] of a solution if the ph = 9.18? 3. poh = -log [OH - ] ph = -log [H 3 O ] ph poh = 14 Kw = [H 3 0 ][OH - ] ph Formula ph Formula [H 3 O ] [OH - ] H 3 O OH - ph poh A or B 7 X X ph poh

5 Strong Acids Strong Acids 1. Completely (100%) dissociates in water 2. Low ph and no K a, single arrow 3. Common Strong Acids HCl HBr HI HNO 3 H 2 SO 4 HClO 4 Eqn/Species HCl H 2 O HNO 3 H 2 O H 2 SO 4 H 2 O (just one proton) Strong Acids Strong Acids 1. What is the ph of M HCl? (Ans: 1.40) 2. What is the ph of M HNO 3? (Ans: 2.40) 3. A soln of HNO 3 has a ph of What is the conc. of the acid? (Ans: M) 4. A soln of HBr has a ph of What is the conc. of the acid? (Ans: M) Strong Bases Strong Bases 1. Soluble Hydroxides. Completely (100%) dissociate in water 2. High ph and no K b 3. Common Strong Bases NaOH KOH Ba(OH) 2 5

6 Strong Bases Weak Acids 1. What is the ph of M NaOH? (Ans: 12.0) 2. What is the ph of M Ca(OH) 2? (Ans: 12.3) 3. What is the molarity of a soln of KOH that has a ph of 11.89? (Ans: ) 1. Do not completely dissociate in water. Higher ph. 2. Equilibrium. Has a K a 3. Some Common Weak Acids HC 2 H 3 O 2 Acetic H 3 PO 4 Phosphoric H 2 CO 3 Carbonic HC 6 H 7 O 6 Ascorbic Weak Acids Weak Acids HC 2 H 3 O 2 H 2 O Eqn/Species/K a 1. What is the ph of M HC 2 H 3 O 2? (Ans: 2.9) HNO 2 H 2 O HSO 4- H 2 O 2. What is the ph of M HC 3 H 5 O 3? (Ans: 2.4) The larger the Ka, the stronger the acid. Weak Acids 3. What is the K a of HCN if a 0.20 M soln has a ph of 5.00? (Ans: 5.0 X ) 4. What is the K a of HF if a 0.10 M soln has a ph of 2.1? (Ans:6.8 X 10-4 ) We buy a gallon of vinegar (acetic acid) and find the ph to be a. Calculate the molarity of the acid. ( M) b. Calculate the grams of acetic acid present in 1 quart of vinegar (1 L = qt). (0.115) c. Calculate the ph of M acetic acid. (1.7) d. Draw a Lewis Dot structure of acetic acid (CH 3 COOH, both oxygen s bonded to the second carbon). e. State the hybridization of each carbon. 6

7 A M solution of citric acid is prepared. a. Calculate the ph of the solution. (2.1) b. Calculate the [OH - ] concentration. (1.17 X10-12 ) c. Experimentally, the ph is measured to be 2.3. Using only the ph and the starting molarity ( M), calculate K a. (2.68 X 10-4 ) d. Calculate the percent error for K a. (64%) e. List the species that would be present in the solution, indicating the major species. % Ionization = [H 3 O ] X 100 [acid] Weak Acids 6. What is the percent ionization of a 0.10 M solution of HCHO 2? (Ans: 4.2%) Weak Acids 7. What is the percent ionization of a M solution of niacin, HC 6 H 4 NO 2? The K a for Niacin is 1.5 X (Ans: 2.7%) 8. What is the K a of HC 2 H 3 O 2 if a 0.30 M solution is 0.77% ionized? (Ans: Ka = 1.8 X 10-5 ) The following questions refer to the weak acid HF (K a = 6.8 X 10-4 ) a. Calculate the ph and moles of F - in 0.400L of 0.400M HF. (1.8, 6.6 X 10-3 moles) b. Calculate the percent ionization for the previous problem. (4.1%) c. Would the major species be HF or F -? d. The % ionization of a new fluorine containing acid (0.200M) is 0.56%. Calculate the K a (6.3 X 10-6 ) e. Why is HF unique among the binary halogencontaining acids? ph and Concentration Acid Review 1. ph depends on a. Strength of the acid b. Concentration (molarity) Show ph from 1 14 (Strong, weak and dilute) 2. Example 0.1 M HCl ph = M HC 2 H 3 O 2 ph = M HCl ph = 2.8 Write the eqns for the dissociation of the following. Indicate all species and write K a if needed HNO 3 HNO 2 HC 7 H 5 O 2 HBr 7

8 1. Do not produce a high concentration of [OH - ] with water 2. Ammonia and Ammonia Derivatives (Amines) NH 3 (CH 3 ) 2 NH CH 3 NH 2 (CH 3 ) 3 N C 5 H 5 N Weak Bases NH 3 H 2 O CH 3 NH 2 H 2 O (CH 3 ) 2 NH H 2 O (CH 3 ) 3 N H 2 O Weak Bases Review 1. What is the ph of M NH 3? (Ans: 11.1) 2. What is the ph of M C 5 H 5 N? (Ans: 8.6) 3. A soln of NH 3 has a ph of What is the molarity? (Ans: M) Write the eqns for the dissociation of the following. Indicate all species and write K a or K b if needed Ca(OH) 2 HC 7 H 5 O 2 HCl C 2 H 5 NH 2 Salts Salts of Weak Bases 1. Finding K b from K a HF H 2 O 2. What is K a for the NH 4 ion? (Ans: 5.6 X ) A. Tend to be positive ions B. Salts of Weak Bases act as acids C. Forming Salts WB CA Salt NH 3 CH 3 NH 2 C 6 H 5 NH 2 8

9 Salts of Weak Bases Salts of Weak Acids NH 4 Cl H 2 O CH 3 NH 3 Br H 2 O C 5 H 5 NHNO 3 H 2 O NH 4 NO 3 H 2 O A. Tend to be negative ions B. Salts of Weak Acids act as bases C. Forming Salts WA CB Salt HC 2 H 3 O 2 HC 3 H 5 O 2 HNO 2 HF Salts of Weak Acids Salts and ph NaClO H 2 O NaF H 2 O Ca(NO 2 ) 2 H 2 O 1. What is the ph of M NaC 2 H 3 O 2? (Ans: 8.4) 2. What is the ph of M NaF? (Ans: 7.6) 3. What is the ph of M NH 4 Cl? (Ans: 5.6) 4. What is the ph of M (CH 3 ) 2 NH 2 Br? (Ans: 6.4) Salts and ph 5. If the ph of a soln of NaC 2 H 3 O 2 is 7.4, what is the concentration? (Ans: M) 6. If the ph of a soln of C 5 H 5 NHNO 3 is 3.6, what is the molarity? (Ans: M) 7. If the ph of C 2 H 5 NH 3 Cl is 6.2, what is the molarity? (Ans: M) 9

10 Write the eqns for the dissociation of the following. Indicate all species and write K a or K b if needed NaOH NaC 3 H 5 O 3 HC 7 H 5 O 2 C 2 H 5 NH 3 NO 3 C 2 H 5 NH 2 HBr Review A solution of HClO is tested and the ph is found to be 4.29 a. Calculate the concentration of HClO in the solution. ( M) b. Would [HClO] or [ClO-] be greater at equilibrium? Justify your prediction. c. NaOH is added to the solution of HClO. Write the reaction that occurs. (Assume the proper ratios are used). d. Water is allowed to evaporate from the solution. What compound is present? e. Calculate how many grams of NaClO must be added to make 2.00 L of a solution with a ph of (Ans: 44.7g) Polyprotic Acids Polyprotic Acids 1. Polyprotic Acids Acids that can donate more than one H 2. Important Examples: H 2 SO 4 - Sulfuric H 3 PO 4 - Phosphoric H 2 CO 3 Carbonic 1. Write eqns and look up K a s for: H 2 SO 4 H 3 PO 4 2. Much less likely to give away 2 nd and 3 rd H ions 3. H 2 CO 3 HCO 3 - CO 3 10

11 Polyprotic Acids Polyprotic Acids 1. Will Na 2 HPO 4 act as an acid or a base in water: (Identify parent acid) HPO 4 H 2 O K b =1.6X10-7 HPO 4 H 2 O K a =4.2X10-13 (Use K a for conj. Acid) 2. Will K 2 HC 6 H 5 O 7 act as an acid or a base in water? 3. Will the following act as acids or bases in water: KHS Na 2 HAsO 4 K 3 C 6 H 5 O 7 Na 3 PO 4 (Calculate/estimate ph, M) Polyprotic Acids Carboxylic Acids 4. What is the ph of M H 2 CO 3? (Ans: 4.40) You generally do NOT have to consider the second or third H for the ph A. Carboxyl Group B. Examples HCO 2 H Formic Acid HC 7 H 4 O 2 Benzoic Acid HC 2 H 3 O 2 Acetic (CH 3 CO 2 H) (CH 3 COOH) Amino Acids Amino Acids A. Amino Acid Structure Glycine 11

12 B. 20 Amino Acids (8 essential, 10 in children) C. Diglycine D. Aspartame (Aspartic acid/ Phenylalanine) E. Sickle Cell Anemia -208 AA protein (1 wrong) -Mutation to help malaria survival rate -Sickle Cell Red Blood Cell Amino Acids Strengths of Binary Acids Acidity increases as you go across More electronegativity difference Bond polarity increase Strength increases as you go down H-X bond strength decreases with size of X X can t hold H as well. Strengths of Oxyacids More electronegative pull makes it more acidic Strengths of Oxyacids More oxygens pull on the H s electrons more. More acidic. HClO K a = 3.0 X 10-8 HIO K a = 2.3 X

13 Hypochlorous H O Cl K a = 3.0 X 10-8 (HClO) Chlorous H O Cl O K a = 1.2 X 10-2 (HClO 2 ) O Chloric H O Cl O Strong Acid (HClO 3 ) O Perchloric H O Cl O Strong Acid O (HClO 4 ) Illustrate how two amino acids form a dipeptide. Be sure to include the byproduct of the reaction Why is perchloric acid (HClO 4 ) a strong acid while hypochlorous acid (HClO) is a weak acid? Draw structures to support you answer. Is the oxalate ion, C 2 O 4-2 a weaker or stronger base than methylamine, CH 3 NH 2? Show all equations and math. K b = 1.6 X for C 2 O -2 4 vs. K b = 4.4 X 10-4 for CH 3 NH 2 Lewis Acids and Bases Lewis Acid Electron Pair Acceptor Lewis Base Electron Pair Donor Coordination Complexes (transition metals) Ni 2 6NH 3 [Ni(NH 3 ) 6 ] 2 Co 2 6NH 3 [Co(NH 3 ) 6 ] 2 1. How much more M NaOH does it take to neutralize a solution of HCl that is ph=2 compared to one that is ph 4? 2. Is M NaOH an appropriate concentration to use for both ph values? Suggest any changes you might want to make. 13

14 ph = 2 [HCl] = 0.01 M Pretend 1 L of HCl Need 833 ml of NaOH ph = 4 [HCl] = M Pretend 1 L of HCl Need 8.33 ml of NaOH M is NOT appropriate for ph =4. Use a a more dilute solution. 3. Which is more acidic: a M solution of HCl or a solution of a weak acid with a ph of 2.32? 4. The volume of an adult stomach is 450 ml. If the ph is 2.0, how many moles of H 3 O are present in the stomach. Assume HCl is the only acid present. NH 4 Cl Na 2 CO 3 KC 2 H 3 O 2 KCl NaH 2 PO 4 16.Produces OH- and accepts a proton 18.a) C 6 H 5 COO - PO 3-4 b) HCO - 3 C 2 H 5 NH 3 20 a) A B CA CB b) A B CB CA c) B A CA CB 22. a) H 2 C 6 H 7 O 5 - H 2 O H 3 C 6 H 7 O 5 OH- H 2 C 6 H 7 O 5 - H 2 O HC 6 H 7 O 5 H 3 O b) H 3 C 6 H 7 O 5 (CA) HC 6 H 7 O 5 (CB) 32.a) [OH-] = 2.2 X (acidic) b) [OH-] = 6.7 X 10-6 (basic) c) [OH-] = 3.2 X 10-8 (acidic) 38. a) H increases, OH - decreases b) ph = 12.1 c) [H ]=3 X 10-7 M, [OH - ] = 4 X 10-8 M 40. ph poh [H] [OH-] A/B X X10-3 B X X10-7 B X X10-11 A X X10-3 B 42.[H ] from 6 X10-6 to 3 X10-6 [OH - ] from 2 X10-9 to 4X

15 44.A) Strong base completely dissociates b) M OHc) False 46. a) 2.87 b) 2.68 c) 2.00 d) a) b) 12.6 c) 10.6 d) M 54.K a = 5.3 X X X 10-4 mol HF (1.0 X 10-3 M HF) 60.[HClO] = 9.0 X 10-3 M 62.a) 4.27 b) 5.98 c) a) 0.721% b) 1.27% c) 2.55 % 74.a) C 3 H 7 NH 3 OH - b) H 2 PO - 4 OH - c) C 6 H 5 CO 2 H OH - 76.[OH-] = 1.5 X 10-3 M ph = a) Kb = 1.6 X 10-6 b) pk b = b) Kb = 1.8 X 10-4 c) CO 3 is stronger base 82. a) Ammonia b) Hydroxylammonium c) K a NH 4 = 5.6 X 10-6, HONH 3 = 9.1X a) ph = 8.09 b) ph = a) Cl more electronegative than S b) P is more electronegative than As c) More O s d) Parent acid e) More O s 96. a) NO - 3 b) PO 3-4 c) CO 3 Ka Kb KH 2 AsO 4 1 X X NaHCO X X 10-8 NaH 2 C 6 H 5 O X X K 2 CO X 10-4 Ca(HC 2 O 4 ) X x10-13 Na 2 S ,000 LiHC 3 H 2 O 4 2 X X NaHSeO X X KHS 1 X X 10-7 KHC 4 H 4 O X X