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Acids and Bases

Acids and Bases. Acids: Compounds that dissociate (give off) one or more hydrogen ions (H+) when dissolved in water (proton donors) Bases: Compounds that dissociate (give off) one or more hydroxide ions (OH-) when dissolved in water (proton acceptors). The pH Scale.

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Acids and Bases

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  1. Acids and Bases

  2. Acids: Compounds that dissociate (give off) one or more hydrogen ions (H+) when dissolved in water (proton donors) Bases: Compounds that dissociate (give off) one or more hydroxide ions (OH-) when dissolved in water (proton acceptors)

  3. The pH Scale pH is a measure of H+ ion concentration. The formula for calculating pH is: pH = -log[H+]

  4. The pH ScalepH = -log[H+] I Do: A solution has a hydrogen ion concentration of 0.001 M. What is the pH of this solution?____ We Do: What is the pH of a solution with a hydrogen ion concentration of 0.0001 M?_______ You Do: What is the pH value of a solution that has a hydrogen ion concentration of 0.0000005 M?_______

  5. The pH Scale Acids have a pH value less than 7. Bases have a pH value greater than 7. Neutral substances have a pH of exactly 7. (Alkaline is another way to say basic)

  6. pH Indicators An indicator is a compound used to detect the presence of H+ ions in solution. Indicators typically change color when exposed to acids and bases and can be used to determine whether a substance is acidic, basic, or neutral. Some common indicators are: Litmus paper (turns red when exposed to acid, blue when exposed to base) Phenolphthalein (clear = acid, pink = base) Universal indicator (red = acid, blue = base) Bromothymol blue (yellow = acid, blue = base) Cyanidin (red cabbage juice) (red = acid, yellow/green = base) Phenol red (yellow = acid, red = base)

  7. Properties of Acids • Acids taste sour • Acids have a pH lower than 7 • Acids effect indicators • Blue litmus turns red • Universal indicator turns red

  8. Properties of Acids • Acids are proton (hydrogen ion, H+) donors • Acids react with active metals, produce H2 • Acids react with carbonates • Acids neutralize bases

  9. Acids Effect Indicators Blue litmus paper turns red in contact with an acid.

  10. Acids Have a pH less than 7

  11. Properties of Bases • Bases taste bitter • Bases have a pH greater than 7 • Bases effect indicators • Red litmus turns blue • Universal indicator turns blue • Phenolphthalein turns purple

  12. Properties of Bases • Bases are proton (H+) acceptors and usually have hydroxide ions- OH- • Solutions of bases feel slippery • Bases neutralize acids

  13. Bases Effect Indicators Red litmus paper turns blue in contact with a base. Phenolphthalein turns purple in a base.

  14. Bases have a pH greater than 7

  15. Common Strong Acids Sulfuric Acid, H2SO4 Perchloric acid, HClO4 Hydrochloric Acid, HCl Hydrobromic Acid, HBr Nitric Acid, HNO3 Hydroiodic Acid, HI

  16. Common Strong Bases Lithium Hydroxide, LiOH Sodium Hydroxide, NaOH Potassium Hydroxide, KOH Calcium Hydroxide Ca(OH)2 Strontium Hydroxide, Sr(OH)2 Barium Hydroxide, Ba(OH)2

  17. Common Weak Acids Formic Acid, HCOOH Acetic Acid, CH3COOH Hydrofluoric, Acid HF Hydrocyanic acid, HCN

  18. Common Weak Bases Sodium hydroxide, NaOH Ammonia, NH3Potassium hydroxide, KOH Calcium hydroxide, Ca(OH)2

  19. Formation of Hydronium ion, H3O+ H3O+ + Cl- H2O + HCl  Proton donor Hydronium Proton acceptor

  20. Acids and Bases Can Be Strong or Weak Strong acids are assumed to be 100% ionized in solution (good proton donors). HCl H2SO4 HNO3 Weak acids are usually less than 5% ionized in solution (poor proton donors). H3PO4 HC2H3O2 Organic acids

  21. Strong Acid Dissociation

  22. Weak Acid Dissociation

  23. Acids Can Be Strong or Weak Which acid is a strong acid?____________ How do you know? Which acid is a weak acid? ___________ How do you know?

  24. Acids and Bases Can Be Concentrated or Dilute A concentrated solution contains a high amount of solute per liter of solution. Example: 12M HCl A dilute solution contains a low amount of solute per liter of solution. Example: 0.01 M HCl

  25. Acids and Bases Can Be Concentrated or Dilute B A Which solution is most concentrated? ___ How do you know? Which solution is lease concentrated?___ How do you know?

  26. Neutralization What happens when an acid is mixed with a base? Neutralization!

  27. Products of Neutralization HCl + NaOH  NaCl + H2O H2SO4 + Ca(OH)2 CaSO4 + 2 H2O The products of neutralization are always a ______ and _______. salt water

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