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

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

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)

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)

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

Properties of Acids  Acids are proton (hydrogen ion, H + ) donors  Acids react with active metals, produce H 2  Acids react with carbonates  Acids neutralize bases

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

Acids Have a pH less than 7

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

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

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

Bases have a pH greater than 7

Common Strong Acids Sulfuric Acid, H 2 SO 4 Perchloric acid, HClO 4 Hydrochloric Acid, HCl Hydrobromic Acid, HBr Nitric Acid, HNO 3 Hydroiodic Acid, HI

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

Common Weak Acids Formic Acid, HCOOH Acetic Acid, CH 3 COOH Hydrofluoric, Acid HF Hydrocyanic acid, HCN

Common Weak Bases Sodium hydroxide, NaOH Ammonia, NH 3 Potassium hydroxide, KOH Calcium hydroxide, Ca(OH) 2

Formation of Hydronium ion, H 3 O + H 2 O + HCl  H 3 O + + Cl - Proton donor Proton acceptor Hydronium

Acids and Bases Can Be Strong or Weak Strong acids are assumed to be 100% ionized in solution (good proton donors). Weak acids are usually less than 5% ionized in solution (poor proton donors). HClH 2 SO 4 HNO 3 H 3 PO 4 HC 2 H 3 O 2 Organic acids

Strong Acid Dissociation

Weak Acid Dissociation

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?

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

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

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

Products of Neutralization HCl + NaOH  H 2 SO 4 + Ca(OH) 2  The products of neutralization are always a ______ and _______. NaCl + H 2 O CaSO H 2 O salt water