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•pH less than 7 •Neutralizes bases(form salts and water) + •Forms H (H3O+) ions in solution •Corrosive-reacts with most metals •Good conductors of electricity •Taste sour HNO3 + H2O H3 + O + NO3 Weak Acids do not ionize completely: Acetic, Boric, Nitrous, Phosphoric, Sulfurous Strong Acids ionize completely: Hydrochloric, Nitric; Sulfuric, Hydriodic • • • • • • HCl- hydrochloric- stomach acid H2SO4- sulfuric acid - car batteries HNO3 – nitric acid - explosives HC2H3O2- acetic acid - vinegar H2CO3-carbonic acid – sodas H3PO4- phosphoric acid -flavorings pH greater than 7 Feels slippery, soapy Taste bitter, chalky Are electrolytes Dissolves fats and oils Usually forms OH ions solution Neutralizes acids in Weak Bases: ammonia; potassium carbonate, sodium carbonate Strong Bases: sodium hydroxide; sodium phosphate; barium hydroxide; calcium hydroxide NaOH- sodium hydroxide (LYE) soaps, drain cleaner Mg (OH)2 - magnesium hydroxide-antacids Al(OH)3-aluminum hydroxide-antacids, deodorants NH4OH-ammonium hydroxide- “ammonia” Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit LecturePLUS Timberlake 9 Describe each solution as: 1) acid 2) base or 3) neutral. A. _1_ soda B. _2_ soap C. _1_ coffee D. _1_ wine E. _3_ water F. _1_ grapefruit LecturePLUS Timberlake 10 Identify each as characteristic of an A) acid or B) base ____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions ____ 3. Chalky taste ____ 4. Is an electrolyte ____ 5. Produces H+ in aqueous solutions LecturePLUS Timberlake 11 Identify each as a characteristic of an A) acid or B) base _A_ 1. Sour taste _B_ 2. Produces OH- in aqueous solutions _B_ 3. Chalky taste A, B 4. Is an electrolyte _A_ 5. Produces H+ in aqueous solutions LecturePLUS Timberlake 12 We use this scale to measure the strength of an acid or base. pH is defined as the –log[H+] pH can use the concentration of hydronium ions or hydrogen ions. SOURCE: http://en.wikipedia.org/wiki/Image:PH_scale.png#file [H+] M 100 10-1 A strong acid 10-2 10-3 10-4 10-6 10-7 10-8 • [H+] is controlled in all biological organisms, and in virtually all biochemical experiments. 10-9 10-10 10-11 10-12 10-14 • Most living cells have a very narrow range of tolerance for pH, i.e. [H+]. • The [H+] concentration will be important (either explicitly or implicitly) for many other topics in biology. 10-5 10-13 pH A strong base • Each pH unit represents a factor of 10 difference in [H+]. The pH scale goes from 0 to 14—because [H+][OH-] = 10-14 14 More acidic More basic pH NaOH, 0.1 M Household bleach Household ammonia Lime water Milk of magnesia Borax Baking soda Egg white, seawater Human blood, tears Milk Saliva Rain Black coffee Banana Tomatoes Wine Cola, vinegar Lemon juice Gastric juice 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 [H1+] 1 x 10-14 1 x 10-13 1 x 10-12 1 x 10-11 1 x 10-10 1 x 10-9 1 x 10-8 1 x 10-7 1 x 10-6 1 x 10-5 1 x 10-4 1 x 10-3 1 x 10-2 1 x 10-1 1 x 100 [OH1-] 1 x 10-0 1 x 10-1 1 x 10-2 1 x 10-3 1 x 10-4 1 x 10-5 1 x 10-6 1 x 10-7 1 x 10-8 1 x 10-9 1 x 10-10 1 x 10-11 1 x 10-12 1 x 10-13 1 x 10-14 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pOH concentration (moles/L) 10-1 pH = 3 OH- H3O+ pH = 7 10-7 H3O+ OH- OH10-14 [H3O+] > [OH-] acidic Timberlake, Chemistry 7th pH = 11 Edition, page 332 H3 O+ [H3O+] = [OH-][H O ] < [OH-] neutral basic 3 + pH = -log [H+] Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 285 Indicator Acid color Neutral color Base color Phenolphthalein Colorless Faint pink Dark pink Bromthymol blue Yellow Green Blue Litmus Red ----- Blue pH paper changes color to indicate a specific pH value. A buffer is a solution that resists changes in pH when small amounts of acids and bases are added. “Heartburn” Planting vegetables and flowers Fish Tanks and Ponds Blood Swimming pools Digestion-process by which foods are broken down into simpler substances. Mechanical digestion-physical process in which food is torn apart (mouth) Chemical digestion- chemical reactions in which large molecules are broken down into smaller molecules. (stomach and small intestines) Mouth-pH around 7. Saliva contains amylase, an enzyme which begins to break carbohydrates into sugars. Stomach- pH around 2. Proteins are broken down into amino acids by the enzyme pepsin. Small intestine-pH around 8. Most digestion ends. Small molecules move to bloodstream toward cells that use them Digestive system mouth esophagus stomach small intestine large intestine