chem lesson 9

• Acids and bases


  Chemical compounds that can be grouped according to their physical and chemical properties
• Properties of acids


  • Taste sour
  • Turn litmus paper red
  • React with some metals to produce hydrogen gas
  • Good conductor of electricity
  • React with carbonates to produce carbon dioxide gas
• Acids in water


  Release hydrogen ions
• (aq)


  (aq)
• Properties of bases (also referred to as alkaline)


  • Taste bitter
  • Feel slippery
  • Turn litmus paper blue
  • Good conductor of electricity
  • Do not react with metals nor carbonates
• Bases in water


  Release hydroxide ions
• Acid formulas


  Begin with one or more hydrogen atoms
• Acid formulas


  • H2SO4 - sulfuric acid
  • HCl - hydrochloric acid
  • H3PO4 - phosphoric acid
• Base formulas


  End with one or more hydroxide ions (OH-)
• Base formulas


  • KOH - potassium hydroxide
  • Ca(OH)2 - calcium hydroxide
• pH scale


  Used to determine how acidic or basic a solution is
• pH


  Represents the "power of Hydrogen", the concentration of hydrogen ions in a solution
• Acids, bases, neutral solutions


  • Acids have pH < 7
  • Bases have pH > 7
  • Neutral solutions have pH = 7
• pH scale


  Logarithmic scale, every 1 unit represents a tenfold effect on the concentration of hydrogen ions
• Concentration of H+ ions

  The higher the concentration, the lower the pH, and the more acidic it is
• Decrease of 1 pH unit

  Represents multiplying the concentration by 10
• pH differences


  • pH 3 is 10 times more acidic than pH 4
  • pH 3 is 100 times more acidic than pH 5
  • pH 3 is 1000 times more acidic than pH 6
  • pH 13 is 10 times more basic than pH 12
  • pH 13 is 100 times more basic than pH 11
  • pH 13 is 1000 times more basic than pH 10
• pH indicators


  Substances that turn different colours at different pH
• pH indicators


  • Litmus, phenolphthalein, universal indicator
• Natural pH indicators


  • Strawberries, red cabbage, hydrangeas
• Neutralization reactions


  Involve the reaction of an acid and a base to produce an ionic compound (a "salt") and water
• Neutralization reactions


  Are a special case of double displacement
• Neutralization reaction


  • HCl + NaOH → HOH + NaCl
• Neutralization reactions


  The hydrogen ion (H+) from the acid combines with the hydroxide ion (OH-) from the base to produce water (HOH)
• Neutralization reactions


  1. HF + LiOH → HOH + LiF

  2. NaOH + HI → HOH + NaI

  3. HI + Be(OH)2 → HOH + BeI2
• Everyday neutralization


  • Stomach acid + antacids
  • Acidic foods + toothpaste
• Acid rain


  • Burning fossil fuels produces CO2, sulfur oxides, and nitrogen oxides
  • These oxides combine with water in clouds to form acids
  • The acids fall to the ground as acid rain
• Effects of acid rain

  • Kills vegetation
  • Changes soil pH
  • Changes water pH
  • Destroys buildings