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Acids and Bases

Acids and Bases. Acids. Bases. OH -. H +. Acid: a substance that gives off H + ions in water. Base: a substance that gives off OH - ions in water. Svante Arrhenius 1859-1927. Init <<5/12/2008 by Daniel R. Barnes.

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Acids and Bases

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  1. Acids and Bases Acids Bases OH- H+ Acid: a substance that gives off H+ ions in water. Base: a substance that gives off OH- ions in water. Svante Arrhenius 1859-1927 Init <<5/12/2008 by Daniel R. Barnes WARNING: This presentation includes a combination of original graphical images created by the author and images taken without specific permission from the world wide web. Do not distribute or copy this presentation.

  2. Acids and Bases Acids Bases OH- H+ H2O Acid: a substance that gives off H+ ions in water. Base: a substance that gives off OH- ions in water.

  3. BASE ACID

  4. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH

  5. + + H H H H H H O O O O O O S Acids and Bases Acids Bases hydronium ion CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH sulfuric acid CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH H3O+ “STRONG” +

  6. Don’t be fooled by the H3. H3PO4 is a strong molecule, so it is a “weak” acid. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 H3PO4 phosphoric acid NaHCO3 NaOH CH3COOH KOH NH3 X HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH

  7. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 acetic acid H3PO4 NaHCO3 NaOH CH3COOH CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH

  8. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH hydrochloric acid

  9. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 nitric acid HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH 721-815 AD Abu Musa Jābir ibn Hayyān

  10. O Acids and Bases Acids Bases H H O C O O O H CH3(CH2)16COONa C H2SO4 H3PO4 C ? O C NaHCO3 ? NaOH H C CH3COOH C ? O H KOH NH3 H H H citric acid HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH

  11. Acids and Bases Acids Bases sodium hydroxide CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH

  12. Acids and Bases Acids Bases CH3(CH2)16COONa sodium stearate H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 + HOOC–CH2–COH(COOH)–CH2–COOH

  13. NEUTRALIZATION Acids and Bases Acids Bases sodium hydrogen carbonate CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 + HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH WATER ACID BASE SALT NaHCO3 + CH3COOH NaCH3COO + CO2 + H2O

  14. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH ammonia CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 ammonium hydroxide HOOC–CH2–COH(COOH)–CH2–COOH

  15. Acids and Bases Acids Bases CH3(CH2)16COONa H2SO4 H3PO4 NaHCO3 NaOH CH3COOH KOH NH3 HCl HNO3 NH4OH Ca(OH)2 HOOC–CH2–COH(COOH)–CH2–COOH

  16. Our notions of Acids and Bases Acids Bases (at least the older definitions of “acid” and “base”) are prejudiced by the fact that Earth is a mostly water-covered planet and, that, consequently, Earth’s creatures, including people, are made mostly of water.

  17. Water molecules are very stable. Nonetheless, every once in a while, a water molecule breaks in two. H2O OH- + H+ The hydrogen and hydroxide ions that water breaks into like each other a lot because of their opposite charges, so they get back together again pretty fast. Therefore, the equation for the dissociation of water deserves a double arrow, since it is a reversible reaction.

  18. Because water molecules rarely break, and because they get back together again so quickly when they do break, the amount of broken molecules in a quantity of pure water is very low. H2O OH- + H+ << 1% > 99.9% The percentages listed here are quite rough. We can be even more precise if we want to.

  19. Because water molecules rarely break, and because they get back together again so quickly when they do dissociate, the amount of broken molecules in a quantity of pure water is very low. H2O OH- + H+ << 1% > 99.9% unbroken broken The percentages listed here are quite rough. We can be even more precise if we want to.

  20. In pure water, the concentration of broken water molecules is 10-7M OH- H+ + That’s the same thing as 10-7 mol/L broken water 10-7 mol/L = 0.0000001 mol/L One liter (L) of water has a mass of 1000 g. The molar mass of water is 18 g/mol. (1000 g)/(18 g/mol) = 55.6 mol, so the concentration of water in water is 55.6 mol/L. (55.6 mol/L)/(10-7 mol/L) = 556,000,000 In pure water, only one out of every 556,000,000 water molecules is broken.

  21. H+ OH- + BROKEN WATER In pure water, only one out of every 556,000,000 water molecules is broken. That’s about 0.002 ppm

  22. - + pH 7 0 14

  23. pH

  24. Click the link below to an FDA web page listing pH’s of different foods. • http://vm.cfsan.fda.gov/~comm/lacf-phs.html pH According to this web page, what is the overwhelming tendency for the pH of foods? Acids Foods tend to be . . .

  25. sour neutral bitter

  26. pH . . . the esoteric version . . . “pH” stands for “potential hydrogen”. (maybe) pH is a weird, numerical way of showing the hydrogen ion concentration in a solution. Mathematically, pH = -log[H+] That’s slightly confusing even if you know what logs are.

  27. log(10n) = n logs log(1000) = 3 log(0.1) = -1 log(10) = 1 log(1) = 0 log(1,000,000) = 6 log(0.0001) = - 4 log(100) = 2 log(1013) = 13 log(50) = 1.6987. . . log(10-5) = -5

  28. pH Let’s give an example of pH: normal water. In normal water, the hydrogen ion concentration is 10-7M. In other words, [H+] = 10-7M. Since pH = -log[H+] . . . The pH of normal water would be 7.

  29. pH In sea water, however, the pH is 8. What would the hydrogen ion concentration be in sea water? In sea water, [H+] = 10-8M. That’s a little more basic than pure water.

  30. pH H2SO4 Car batteries are filled with very dangerous sulfuric acid. In battery acid, one of the most corrosive acids there is, the hydrogen ion concentration is about 1M. 1 = 100, so . . . In battery acid, the pH is . . . 0

  31. pH Lemon juice is one of the most acidic foods you can eat. In lemon juice, the hydrogen ion concentration is about 10-2M. 2 In lemon juice, the pH is . . . That’s not as strong as battery acid, but it can still rot your teeth.

  32. pH Sodium hydroxide is a strong base. It’s also known as “lye” and turns fat into soap, which makes it a handy drain opener. In a concentrated sodium hydroxide solution, the hydrogen ion concentration can be about 10-14M. In such a concentrated solution of sodium hydroxide, the pH is . . . 14

  33. pH A typical pH for vinegar is 3. What would the hydrogen ion concentration be in vinegar? In vinegar, [H+] = 10-3M. That’s not quite as acidic as lemon juice or battery acid, but that’s still pretty sour.

  34. High [H+] Low pH H+ Acids Low [H+] High pH

  35. High [OH-] Low pOH OH- Low p #'s = High Concentrations High p #'s = Low Concentrations Bases Low [OH-] High pOH

  36. H2O OH- + H+

  37. Unless disturbed, aqueous (watery) systems, such as a cup of water, an ocean, a car battery, or your bloodstream, will tend reach a state of equilibrium, in which the forward and reverse reactions shown below occur at equal rates. H2O OH- + H+ Equilibrium: when opposite processes occur at equal rates. Amounts of different chemicals are probably not equal to each other. However, at equilibrium, the amount of each chemical does not change as time goes by. At equilibrium, water molecules fall apart but they come back together again just as quickly as they fall apart.

  38. LeChatelier’s Principle H2O OH- + H+ If a system is at equilibrium, the amount of each chemical will remain constant as time goes by. However, if a system at equilibrium is disturbed by some kind of stress, the reaction rates will change in whatever way will oppose the effects of the disturbance. If a bunch of molecules are at equilibrium and you disturb them, the molecules will try to undo the work you have done.

  39. LeChatelier’s Principle H2O OH- + H+ Imagine a bathtub full of water. If not disturbed, it will reach an equilibrium with regard to the above reversible reaction. H+ = 3 OH- = 3

  40. LeChatelier’s Principle Cl Cl Cl H2O OH- + H+ However, if you raise the [H+], say, by pouring in some hydrochloric acid, this will disturb the equilibrium. Didn’t you see us being in equilibrium? RUDE! Sa-kurity! Oh no you di-ent just add more H+! H+ = 3 6 OH- = 3

  41. LeChatelier’s Principle Cl Cl Cl H2O OH- + H+ The system will now do whatever it takes to lower the [H+], to undo what you just did . . . at least partially . . . H+ = 3 6 OH- = 3

  42. LeChatelier’s Principle Cl Cl Cl H2O OH- + H+ The equilibrium, as they say, will “shift to the left”. Why? The forward reaction creates H+, but the reverse reaction (going to the left) uses up H+, turning it into water. Did you notice that by adding H+, you made OH- decrease? 1 H+ = 3 6 4 OH- = 3

  43. It is generally true that if you make [H+] increase, you will cause a decrease in [OH-]. This is expressed mathematically by the following equation: [H+][OH-] = 10-14M2 If two numbers always multiply to give the same result, then when one of the two numbers gets bigger, the other must get smaller. Take the following example: 1 x 24 = 24 2 x 12 = 24 3 x 8 = 24 4 x 6 = 24 6 x 4 = 24

  44. It is generally true that if you make [H+] increase, you will cause a decrease in [OH-]. This is expressed mathematically by the following equation: [H+][OH-] = 10-14M2 Now try some acid-base examples. These examples could be any aqueous (watery) system. If [H+] = 10-3M, then [OH-] = 10-11M 1 x 24 = 24 If [H+] = 10-12M, then [OH-] = 10-2M 2 x 12 = 24 If [H+] = 10-1M, then [OH-] = 10-13M 3 x 8 = 24 If [H+] = 10-7M, then [OH-] = 10-7M 4 x 6 = 24 If [H+] = 1M, then [OH-] = 10-14M 6 x 4 = 24

  45. It is generally true that if you make [H+] increase, you will cause a decrease in [OH-]. This is expressed mathematically by the following equation: [H+][OH-] = 10-14M2 Now, just for fun and review, tell me the pH for each of the following solutions, and tell me if it’s acid, base, or neutral. pH = 3 (acid) If [H+] = 10-3M, then [OH-] = 10-11M If [H+] = 10-12M, then [OH-] = 10-2M pH = 12 (base) If [H+] = 10-1M, then [OH-] = 10-13M pH = 1 (acid) If [H+] = 10-7M, then [OH-] = 10-7M pH = 7 (neutral) If [H+] = 1M, then [OH-] = 10-14M pH = 0 (acid)

  46. pH pH + pOH = 14 If the pH of a concentrated sodium hydroxide solution is 14, Then the pOH is . . . zero High pOH Low pH = acid (<< 7) pH of 7 = neutral (like water) Medium pOH High pH = base (>7) Low pOH

  47. High [H+] or low [H+]? High [OH-] or low [OH-]? High pH or low pH? High pOH or low pOH? H+ H+ Acid, base or neutral? H+ H+ H+ H+ H+ OH-

  48. High [H+] or low [H+]? High [OH-] or low [OH-]? High pH or low pH? High pOH or low pOH? H+ H+ Acid, base or neutral? OH- OH- H+ OH- OH- OH- OH- H+ OH-

  49. High [H+] or low [H+]? medium medium High [OH-] or low [OH-]? = 7 medium High pH or low pH? High pOH or low pOH? medium = 7 H+ OH- Acid, base or neutral? OH- H+ OH- H+ OH- H+ OH- H+

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