Lecture Notes: Strengths of Acids and Bases

Introduction

• Acids donate protons (H+), while bases accept protons.
• The strength of acids or bases depends on their ability to donate or accept protons in water.

Strong Acids

• Definition: Completely dissociate in water; no reverse reaction.
• Key Example: Hydrochloric acid (\text{HCl}) dissociates fully into (\text{Cl}^-) and (\text{H}_3\text{O}^+).
• List of Six Strong Acids:
  • Nitric Acid (\text{HNO}_3)
  • Sulfuric Acid (\text{H}_2\text{SO}_4)
  • Perchloric Acid (\text{HClO}_4)
  • Hydrochloric Acid (\text{HCl})
  • Hydrobromic Acid (\text{HBr})
  • Hydroiodic Acid (\text{HI})_

Strong Bases

• Definition: Completely dissociate in solution, forming hydroxide ions.
• Common Strong Bases: Typically from Group 1 and 2 elements, e.g., calcium hydroxide (\text{Ca(OH)}_2), sodium hydroxide (\text{NaOH}), barium hydroxide (\text{Ba(OH)}_2).

Electrolytes

• Strong acids and bases are strong electrolytes, conducting electricity well.
• Conductivity comparison:
  • Strong electrolyte: bright light bulb.
  • Weak electrolyte: dim light bulb.
  • Non-electrolyte: no light.

Weak Acids and Bases

• Definition: Partially dissociate in solution; reversible reactions.
• Characteristics:
  • Produce few ions, thus weak electrolytes.
  • Reversible reaction indicated by double arrows.
  • Most acids and bases are weak except the strong ones listed.
  • Example of weak base: Ammonia (\text{NH}3).

Le Chatelier's Principle

• Reactions shift to counteract disturbances:
  • Adding/removing substances affects reaction direction.
  • Forward reaction: shifts right.
  • Reverse reaction: shifts left.

Equilibrium and Reaction Shifts

• Ammonia Reaction Example:
  • Base in aqueous solution forms an equilibrium with water.
  • Added hydroxide ions cause shift left (towards reactants).
  • Removing ammonia shifts the reaction right (towards products).

Conclusion

• Memorize strong acids and bases to understand others as weak.
• Apply understanding of equilibria and Le Chatelier's principle to predict reaction shifts.