Ionic Equilibrium Quick Revision Sheet

Key Concepts

• Electrolytes: Substances that ionize in solution to conduct electricity.
  • Strong Electrolytes: Completely ionize (e.g., NaCl, HCl).  
  • Weak Electrolytes: Partially ionize (e.g., CH₃COOH).  
   
• Ionic Equilibrium: The state where the rate of ionization is equal to the rate of recombination of ions.
• Dissociation Constant (Ka/Kb): Measures the extent of ionization of a weak acid/base.
  • Larger Ka/Kb: Stronger acid/base.  
• pH and pOH: Measures acidity/basicity of a solution.
  • pH = -log[H+]  
  • pOH = -log[OH-]  
  • pH + pOH = 14  
   

Acid-Base Theories

• Arrhenius Theory: Acids produce H+ ions, bases produce OH- ions.  
• Brønsted-Lowry Theory: Acids donate protons (H+), bases accept protons.  
• Lewis Theory: Acids accept electron pairs, bases donate electron pairs.  

Ionic Product of Water (Kw)

• Kw = [H+][OH-] = 1.0 × 10^-14 at 25°C  

Buffer Solutions

• Solutions that resist changes in pH upon addition of small amounts of acid or base.  
• Composed of a weak acid and its conjugate base, or a weak base and its conjugate acid.  
• Henderson-Hasselbalch Equation: pH = pKa + log([A-]/[HA])  

Solubility Product (Ksp)

• The product of the molar concentrations of ions in a saturated solution of a sparingly soluble salt.
• Ksp > Q: Solution is unsaturated.
• Ksp = Q: Solution is saturated.  
• Ksp < Q: Precipitate will form.

Salt Hydrolysis

• The reaction of a salt with water to produce an acidic or basic solution.
• Salts of strong acid and strong base undergo neutral hydrolysis.
• Salts of strong acid and weak base undergo acidic hydrolysis.
• Salts of weak acid and strong base undergo basic hydrolysis.

Common Ion Effect

• The addition of a common ion to a solution containing a weak electrolyte decreases the degree of ionization of the weak electrolyte.  

Applications of Ionic Equilibrium

• Titrations: To determine the concentration of an unknown solution.  
• Buffer systems: To maintain a constant pH in biological systems and chemical processes.  
• Solubility: To predict the formation of precipitates.

Remember: Ionic equilibrium involves dynamic processes where ions are constantly being formed and recombining. Understanding these concepts is crucial for mastering acid-base chemistry and other related topics.