1 Acids and Bases Acids and Bases

2 Acids and bases are encountered frequently both in chemistry and in everyday living. They have opposite properties and have the ability to cancel or neutralize each other. Acids and bases are carefully regulated in the body by the lungs, blood, and kidneys through equilibrium processes.

3 Vinegar contains acetic acid, which makes it taste sour. Onions release a gas which turns into sulfuric acid when it reaches your eyes, making them burn.

4 Soap, baking soda, milk of magnesia, and ammonia all contain bases. These substances exhibit some of the physical properties of bases, such as feeling slippery, tasting bitter, and dissolving greases. Bases also irritate the skin and eyes just as acids do.

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8 Some Properties of Acids 1. Arhenius Theory: Acids produce H + ions in water: HCl => H + + Cl - 2. Taste sour 3. Corrode metals 4. Conduct electricity: Electrolytes 5. React with bases to form a salt and water HCl + NaOH => NaCl + H 2 O 6. pH is less than 7 7. Change color of indicators

9 Common Acids Acetic acid (CH 3 COOH): vinegar Acetylsalicylic acid (HOOCC 6 H 4 OOCCH 3 ): aspirin Ascorbic acid (H 2 C 6 H 6 O 6 ): vitamin C Carbonic acid (H 2 CO 3 ): soft drinks, seltzer water Citric acid (C 6 H 8 O 7 ): citrus fruits, artificial flavorings Hydrochloric acid (HCl): stomach acid Nitric acid (HNO 3 ): fertilizer, explosives Sulfuric acid (H 2 SO 4 ): car batteries

10 Common Bases Aluminum hydroxide (Al[OH] 3 ): antacids, deodorants Ammonium hydroxide (NH 4 OH): glass cleaner Magnesium hydroxide (Mg[OH] 2 ): laxatives, antacids Sodium bicarbonate/sodium hydrogen carbonate (NaHCO 3 ): baking soda Sodium carbonate (Na 2 CO 3 ): dish detergent Sodium hydroxide (NaOH): lye, oven and drain cleaner Sodium hypochlorite (NaClO): bleach

11 Acids have a pH less than 7

12 12 The pH Scale

13 Naming Acids

14 als/Naming/Acids.htm Anion name Acid name hypo___ite hypo___ous acid ___ite ___ous acid ___ate ___ic acid per___ate per___ic acid

15 Name of AnionName of AcidExamples.....-ideHydro.....-ic acidHBr bromide → hydrobromic acid Per.....-atePer.....-ic acidHClO 4 perchlorate → perchloric acid.....-ate.....-ic acidHClO 3 chlorate → chloric acid H 2 SO 4 sulfate → sulfuric acid.....-ite.....-ous acidHClO 2 chlorite → chlorous acid H 2 SO 3 sulfite → sulfurous acid Hypo...-iteHypo....-ous acidHClO hypochlorite → hypochlorous acid

16 HBr (aq)HBr (aq) H 2 CO 3H 2 CO 3 H 2 SO 3H 2 SO 3 H 2 SO 4H 2 SO 4  hydrobromic acid  carbonic acid  sulfurous acid Acid Nomenclature Review  Sulfuric acid

17 Some Properties of Bases  Produce OH - ions in water: NaOH => Na +1 + OH -1 NaOH => Na +1 + OH -1  Taste bitter, chalky  Are electrolytes  Feel soapy, slippery  React with acids to form salts and water  pH greater than 7  Change color of indicators

18 Common Bases NaOHsodium hydroxidelye KOHpotassium hydroxideliquid soap Ba(OH) 2 barium hydroxidestabilizer for plastics Mg(OH) 2 magnesium hydroxide“MOM” Milk of magnesia Al(OH) 3 aluminum hydroxideMaalox (antacid) Al(OH) 3 aluminum hydroxideMaalox (antacid)

19 Acid/Base definition Arrhenius (traditional) Acids – produce H + ions in aqueous solution Bases – produce OH - ions in aqueous solution

20 Concentration of a Solution An aqueous solution consists of at least two components, the solvent (water) and the solute (the stuff dissolved in the water). Usually one wants to keep track of the amount of the solute dissolved in the solution. We call this the concentration.

21 The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the acid. The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the acid. pH = - log [acid]

22 Concentration, M The amount of solute in a solution is given by its concentration, or molarity M = n / V and n = m / MM M = n / V and n = m / MM Molarity (M) = moles solute liters of solution

23 2.A basic solution was made by dissolving 15g of cadmium III hydroxide in 390 mL of water. What is the pH?

24 pH = -log [H + ] [ H + ] = 10 -pH pOH = -log [OH - ] [ OH - ] = 10 -pOH pH + pOH = 14 [H] [OH] = 1 x pH Formulas

25 Calculating the pH pH = - log [H + ] (Remember that the [ ] means Molarity) For HCl, [ H + ] = [HCl] For H 2 SO 4, [ H + ] = 2 x [H 2 SO 4 ]

26 Try These! Find the pH of these: 1)A 0.15 M solution of Hydrochloric acid. 2) A 3.00 X M solution of Sulfuric Acid. 3) A 1.2 x M solution of Aluminum hydroxide

27 pH calculations – Solving for H+ If the pH of Coke is 3.12, What is [H + ] = ???

28 pH calculations – Solving for H+ A solution has a pH of 8.5. What is the Molarity of hydrogen ions in the solution?A solution has a pH of 8.5. What is the Molarity of hydrogen ions in the solution?

29 [H 3 O + ], [OH - ] and pH What is the pH of the M NaOH solution?

30 The pH of rainwater collected in a certain region of the northeastern United States on a particular day was What is the H + ion concentration of the rainwater? The OH - ion concentration of a blood sample is 2.5 x M. What is the pH of the blood?

31 [OH - ] [H + ] pOH pH 10 -pOH 10 -pH -Log[H + ] Log[OH - ] -Log[OH - ] 14 - pOH 14 - pH 1.0 x [OH - ] [OH - ] 1.0 x [H + ] [H + ]

32 Calculating [H 3 O + ], pH, [OH - ], and pOH Problem 1: A chemist dilutes concentrated hydrochloric acid to make two solutions: (a) 3.0 M and (b) M. Calculate the [H 3 O + ], pH, [OH - ], and pOH of the two solutions at 25°C. Problem 2: What is the [H 3 O + ], [OH - ], and pOH of a solution with pH = 3.67? Is this an acid, base, or neutral? Problem 3: Problem #2 with pH = 8.05?

33 pH testing There are several ways to test pHThere are several ways to test pH –Blue litmus paper (red = acid) –Red litmus paper (blue = basic) –pH paper (multi-colored) –pH meter (7 is neutral, 7 base) –Indicators like phenolphthalein –Natural indicators like red cabbage

34 pH indicators Indicators are dyes that will change color in the presence of an acid or base Some indicators only work in a specific range of pH Some dyes are natural, like red cabbage. em/indtbl.htmhttp://dept.sfcollege.edu/natsci/ch em/indtbl.htm

35 LAB: Red Cabbage, Bromothymol Blue or pH paper ???

36 Phenophtalein & Bromothymol Blue

37 SampleRed Cabbage pH Bromothy mol Blue pH paperAcidic or Basic 1. Milk 2.Orange Juice

38 pH meter Tests the voltage of the electrolyteTests the voltage of the electrolyte Converts the voltage to pHConverts the voltage to pH Very cheap, accurateVery cheap, accurate Must be calibrated with a buffer solutionMust be calibrated with a buffer solution