Acids and Bases Sour, bitter Soft, slippery Base Acid Base Base Acid 8. Milk 3. lemonade 5: Milk of magnesia Base Acid 6. Baking Soda Base 10. Vinegar Base Acid 1. oranges Acid ACIDS and BASES “In nature, acids can be found in fruits: citric acid is responsible for the sharp taste of lemons. Vinegar contains acetic acid, and tannic acid from tree bark is used to tan leather. The stronger mineral acids have been prepared since the Middle Ages. One of these, aqua fortis (nitric acid), was used by assayers to separate gold from silver. Car batteries contain sulfuric acid, also strong and corrosive. A base is the opposite of an acid. Bases often feel slippery; bicarbonate of soda and soap are bases, and so is lye, a substance that can burn skin. Bases that dissolve in water are called alkalis. In water, acids produce hydroxide ions. When an acid and a base react together, the hydrogen and hydroxide ions combine and neutralize each other, forming water together and a salt. The strength of acids and bases can be measured on a pH scale.” Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 42 Acid 4. Tea 11. tomatoes 2. lemons 9. Baking powder 7. Batteries Acid Acid Acid Acid Base

What is water? H2O Is it H-O-H, or is it H+OH-? covalent Both! ionic H-O-H (l) H+ (aq) + OH- aq) Keq = [H+][OH-] = Kw = 10-14 M pH = 7 Pure water: [H+] = [OH-] = 10-7M pH < 7 = acidic pH > 7 = basic

Exponent Math and Water [10-7][10-7] [10-14] [H+] [OH-] [103][10-7] [10-4] [10-7] [10-7] 7 (n) pOH: 7 pH: [103][107] [1010] [10-3] [10-11] pH: 3 (a) 11 pOH: [10-3][10-11] [10-14] [10-5] [10-9] pH: 5 (a) pOH: 9 102 [10-13] 10-1 13 (b) pOH: 1 pH:

Sometimes there is just no avoiding using your calculator… Find the hydroxide ion concentration of a 3.0  10-2 M HCl solution. L1 only [H+][OH-] = 1.0  10-14 [3.0  10-2][OH-] = 1.0  10-14 [OH-] = 3.3  10-13 M What is the pH of that solution?...

Logarithms and pH L1 only 10-2 = 0.01 102 = 100 -2 is the log of 0.01 Conclusion: logarithms are exponents If [H+] = 10-2 then pH = 2 So… 10-pH = [H+] pH = -log [H+] Simililarly: 10-pOH = [OH-] pOH = -log [OH-]

pH and H+ concentration 10-pH = [H+] pH = -log [H+] L1 only pH [H+] [H+] pH 7 10-7 10-4 4 3 10-3 0.1 -log 0.10 = 1 3.4 10-3.4=3.98 x 10-4 0.84 -log 0.84 = 7.5 x 10-2 12.62 10-12.62=2.40 x 10-13 4 -log 4 = -6 x 10-1

Use the change sign (-) button, not the subtract button pH + pOH = 14 [H+] = 10-pH pH = -log [H+] [OH-] = 10-pOH pOH = -log [OH-] [H+][OH-] = 10-14 L1 only [H+][OH-] = 10-14 Enter 10^-14/1.66E-4 Acid or base? Example pH [H+] pOH [OH-] 3.78 1.66 x 10-4 10.22 6.0 x 10-11 Acid Orange juice pH>7 = base pH<7 = acid pH + pOH = 14 [H+] = 10-pH Enter 14-3.78 Enter 10^-3.78 Use the change sign (-) button, not the subtract button

Neutralization HCl + NaOH  NaCl + H2O Acid base Salt water HBr NaOH NaBr H2O 2 HBr Mg(OH)2 MgBr2 2 H2O HNO3 KOH KNO3 H2O

20.00 mL HNO3 is neutralized with 43.33 mL of 0.1000M KOH. I have 20 mL of nitric acid. I’m scared. I have no idea how concentrated it is. How can I find out? Titration (movie) Neutralize it with a base of known concentration. Molarity known x liters known Molarity unknown = Liters unknown 20.00 mL HNO3 is neutralized with 43.33 mL of 0.1000M KOH. [HNO3] ? 43.33 x 0.1/20 = 0.2167 M