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Name: _____________ Period: _______ Acids and Bases March 25 www.coolscienceclass.com 28 29 30 Acids and Bases Unit Begins 31 Apr 1 4 5 Acids and Bases Unit Ends Unit Test Packet & Homework Due 6 Review 7 Review 8 3rd Quarter Ends End of Quarter test La Habra High Spring Break! YEAH!!!! 5. Acids, bases, and salts are three classes of compounds that form ions in water solutions. As a basis for understanding this concept: a. Students know the observable properties of acids, bases, and salt solutions. b. Students know acids are hydrogen-ion-donating and bases are hydrogen-ion-accepting substances. c. Students know strong acids and bases fully dissociate and weak acids and bases partially dissociate. d. Students know how to use the pH scale to characterize acid and base solutions. e. * Students know the Arrhenius, Brønsted-Lowry, and Lewis acid–base definitions. f. * Students know how to calculate pH from the hydrogen-ion concentration. Math Review: Logarithms N = 10x log N = x N = antilog x Practice 1: Use your calculator, find out the following logarithms: a) 10-3, b) 2.0 x 10-5, c) 0.0056, d) 5000, e) 3.8 x 109 Practice 2: Use your calculator, find out the following values: a) 0.50, b) -3.00, c) 2.5, d) -7.9 1 Acid Base Comparison Table Acid Base Properties Sour taste Give sharp stinging pain in a cut or wound. Corrosive – burns skin Bitter taste Slippery feel Corrosive – cause deep, painful, slow-healing wound Indicator Acid Solution Neutral Solution Basic Solution Litmus Bromothymol Blue Phenolphthalein Universal Indicator red yellow clear red purple blue clear yellow-green blue blue purple purple pH Scale Examples Common Acid Hydrochloric acid Sulphuric acid Stomach juice Lemons Vinegar Apples Oranges Grapes Sour milk White bread Fresh milk pH 0.1 0.3 1-3 2.3 2.9 3.1 3.5 4 4.4 5.5 6.5 Common Bases Human saliva Distilled water Blood plasma Eggs Seawater Borax Milk of magnesia Ammonia water Limewater Caustic soda pH 6-8 7 7.4 7.8 7.9 9.2 10.5 11.6 12.4 14 2 Theory Arrhenius Arrhenius acid – any compound when mixed in solution that will give off H+ ions Arrhenium base – any compound when mixed in solution that will give off OHions Brønsted-Lowry Bronsted-Lowry acid – any compound when mixed in solution which donates or gives up a proton (H+) Acid H+ producer Base OH- producer Example: HCl→H+ + Cl- Example: NaOH→Na+ + OHHighly solubility in water NaOH – lye, drain opener, Easy Off KOH Acids that contains x ionizable hydrogens. Only the hydrogens in very polar bonds are ionizable. Monoprotic acids HNO3, CH3COOH Diprotic acids H2SO4 Triprotic Acids H3PO4 Low solubility in water Ca(OH)2 – 0.165g Mg(OH)2 – 0.0009g – milk of magnesia, antacid + H donor H+ acceptor Example: 1) H2O, 2) HCl Example:1) NH3, 2) H2O + 1) NH3(aq) + H2O(l) ↔NH4 (aq) + OH-(aq) 2) HCl(g) + H2O(l) ↔ H3O+(aq) + Cl-(aq) Bronsted-Lowry base – any compound when mixed in 3) HCO3-(l)+ H2O(l) ↔ H3O+(aq) + CO3-2 (aq) solution which accepts or takes a proton (H+) Amphoteric: a substance which may serve as either an acid or a base. H2O is an example of an amphoteric substance because Conjugate acid – formed on the it may either donate its H+ or accept an H+ from another product side of a reaction from substance. the base of the reactants side; Conjugate Acid-Base Pairs formed when the base accepts Acid Base the proton HCl Cl HSO4Conjugate base – formed on the H2SO4 H3O+ H2O product side of a reaction from HSO4 SO4-2 the acid of the reactants side; formed when the acid donates its CH3COOH CH3COOproton H2CO3 HCO3HCO3CO3-2 NH4+ NH3 H2O OH- 3 Lewis electron-pair acceptor electron-pair donor Lewis Acid: a substance that can accept a pair of electrons to form a covalent bond Lewis Base: a substance that can donate a pair of electrons to form a covalent bond Problem 1. Identify the Lewis acid and Lewis base in each reaction: a) H+ + H2O → H3O+ b) AlCl3 + Cl- → AlCl4- Hydrogen Ions from Water Self-ionization: H+ always joins with a water molecule: For aqueous solutions, the ion-product constant for water (Kw) Kw = [H+] x [OH-] = 1.0 x 10-14 Problem 2. Colas are slight acidic. If the [H+] in a solution is 1.0 x 10-5M, is the solution acidic, basic or neutral? What is the [OH-] of this solution? 4 Calculating pH and pOH pH scale – a scale from 0 – 14, which measures whether a substance is acidic or basic. 7 is a neutral pH, below 7 is acidic, and above 7 is basic. The father away from 7, the acid or base is the stronger the substance is. (Refer to the pH scale on page 2) pH – measure of “parts Hydrogen”; measures the strength of an acid or a base by measuring the concentration of the hydrogen ion in solution pOH – measure of “parts Hydroxide” indicator – a substance which can measure whether a substance is an acid or base; usually involves a color change Formula Ion concentration pH pH = -log[H+] [H+] = antilog pH [H+] is the molarity of hydrogen ion pH = 14 - pOH pOH pOH = -log[OH-] [OH-] = antilog pOH [OH-] is the molarity of hydroxide ion pOH = 14 - pH pH + pOH = 14 Problem 3. What is the pH of a solution with a hydrogen-ion concentration of 4.2 x 10-10M? Problem 4. The pH of an unknown solution is 6.35. What is its hydrogen-ion concentration? Problem 5. What is the pH of a solution if [OH-] = 4.0 x 10-11 M? 5 Strong Acids/Bases: compounds which dissociate (break up into ions) completely or to a great extent when placed in solution Weak Acids/Bases: compounds which dissociate (break up into ions) very little, poorly in solution Relative Strengths of Common Acids and Bases Problem 6. Which acid in the above table would you expect to have the lowest degree of dissociation? Which base would have the lowest degree of dissociation? Neutralization Reaction: the type of reaction found in acid/base chemistry; occurs when an acid reacts with a base forming neutral compounds such as salt and water. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(l) Problem 7. What are the products of a reaction between an acid and a base? 6 Name: ________________ Period: _______ Acids and Bases Classwork True or False ____ 1. Hydrochloric acid is a strong acid that is diprotic. ____ 2. A Bronsted-Lowry base is a hydrogen-ion acceptor. ____ 3. A compound can act as both an acid and a base. ____ 4. If the [H+] in a solution increases, the [OH-] must decrease. ____ 5. The [OH-] is less than 10-7M in a basic solution ____ 6. Acids are completely dissociated in aqueous solution. ____ 7. The reaction of an acid and a base produces only water. Matching ____ 8. Lewis base a. acids that contain three ionizable hydrogens ____ 9. hydronium ion (h3o+) b. aqueous solution in which [h+] and [oh-] are equal ____ 10. triprotic acids c. bases that do not dissociate completely in aqueous solution ____ 11. conjugate base d. solution in which [h+] is greater than [oh-] ____ 12. neutral solution e. an electron-pair donor ____ 13. acid solution f. particles that remains when an acid has donated a hydrogen ion ____ 14. strong acids g. a water molecule that gains a hydrogen ion ____ 15. weak base h. acids that ionize completely in aqueous solution Multiple Choice ____ 15. The pH of a sample of orange juice is 3.5. A sample of tomato juice has a pH of 4.5. Compared to the [H+] of orange juice, the [H+] is a. 1.0 times higher b. 10 time lower c. 10 times higher d. 1.0 time lower ____ 14. Which species is the conjugate base of an ammonium ion, NH4+? a. H2O ____ b. OH- c. NH3 d. H3O+ 15. A solution with a hydrogen ion concentration of 2.3 x 10-8M has a pH between a. 2 and 3 b. 3 and 4 c. 7 and 8 d. 8 and 9 7 ____ 16. The net ionic equation for the neutralization reaction between solutions of potassium hydroxide and hydrochloric acid is: a. H+(aq) + OH-(aq) → H2O(l) b. KOH(aq) + HCl(aq) → H2O(l) + KCl(aq) c. K+(aq) + Cl-(aq) → KCl(aq) d. K+(aq) + OH-(aq) + H+(aq) + Cl-(aq) → KCl(aq) + H2O(l) ____ 17. What are the concentrations of H+ and OH- in pure water at 25ºC? a. 1.0 x 10-5 and 1.0 x 10-7 b. 1.0 x 10-7 and 1.0 x 10-5 c. 1.0 x 10+7 and 1.0 x 10-7 d. 1.0 x 10-7 and 1.0 x 10-7 Calculations, etc. Show work: 18. Calculate the pH for the following solutions and indicate whether each solution is acidic or basic. (Circle one) a. [H+] = 1 x 10-2M Acid/Base pH = b. [OH-] = 1 x 10-2M Acid/Base [H+] = pH = - c. [OH ] = 1 x 10-8M Acid/Base [H+] = pH = 19. What are the hydroxide-ion concentrations for solutions with the following pH/pOH values? Are they acidic or basic? Circle the appropriate ones. a. pH = 4.00 [H+] = Acid/Base b. pOH = 8.50 pH = Acid/Base [H+] = c. pH = 11.2 Acid/Base [H+] = 20. Write the formula for the conjugate base of each acid. a. H2SO4 b. HCN 21. Write the formula and name of the conjugate acid of each Bronsted-Lowry acid. a. ClO2-1 b. H2PO4-1 8