8.4 - Strong and Weak Acids and Bases

• Acid and Base Strength

  The strength of an acid or base is determined by its extent of ionization in water. Strong acids and bases ionize completely, while weak acids and bases only partially ionize.
• Ionization of Strong Acids and Bases

  Strong acids and bases dissociate entirely into their ions in aqueous solutions, producing a high concentration of $H^+$ or $OH^-$ions, respectively. Examples include HCl (hydrochloric acid) and NaOH (sodium hydroxide).
• Ionization of Weak Acids and Bases

  Weak acids and bases only partially dissociate in water, resulting in a low concentration of $H^+$ or $OH^-$ ions and the presence of undissociated molecules in the solution. Examples include CH3COOH (acetic acid) and NH3 (ammonia).
• Commonality of Weak Acids and Bases

  Weak acids and bases are more common than strong ones in nature and biological systems.
• Distinguishing Between Strong and Weak Bases: Conductivity

  Conductivity measures a solution's ability to conduct electricity, which depends on the concentration of ions present. Weak acids and bases ionize partially in solution, leading to lower conductivity compared to strong acids and bases, which dissociate completely and produce more ions.
• Distinguishing Between Strong and Weak Bases: pH

  pH is a direct indicator of the acidity or basicity of a solution and can be used to distinguish between strong and weak acids and bases. Strong acids and bases change the pH of a solution more significantly upon dilution due to their complete ionization. Weak acids and bases result in less dramatic changes in pH when diluted, as the equilibrium between the ionized and unionized forms adjusts to partially restore the ion concentration.
• Distinguishing Between Strong and Weak Bases: Rate of Reaction

  The rate of reaction involving acids or bases can indicate their strength. Strong acids and bases, due to their higher concentration of $H^+$ions, typically participate in reactions more quickly and completely than weak acids and bases.
• Is this a weak or strong acid - Hydrochloric Acid (HCl)?

  Strong Acid
• Is this a weak or strong acid - Acetic/ethanoic Acid (CH3COOH)?

  Weak Acid
• Is this a weak or strong acid - Sulfuric Acid (H2SO4)?

  Strong Acid
• Is this a weak or strong acid - Carbonic Acid (H2CO3)?

  Weak Acid
• Is this a weak or strong base - Sodium Hydroxide (NaOH)?

  Strong Base
• Is this a weak or strong base - Ammonia (NH3)?

  Weak Base
• Is this a weak or strong base - Potassium Hydroxide (KOH)?

  Strong Base
• Is this a weak or strong base - Methylamine (CH3NH2)?

  Weak Base
• Is this a weak or strong acid - Nitric Acid (HNO3)?

  Strong Acid
• Is this a weak or strong acid - Phosphoric Acid (H3PO4)?

  Weak Acid
• Is this a weak or strong base - Lithium Hydroxide (LiOH)?

  Strong Base
• Is this a weak or strong base - Barium Hydroxide (Ba(OH)2)?

  Strong Base
• Is this a weak or strong base - Ethylamine (C2H5NH2)?

  Weak Base