Neutralization Reactions and Hydrolysis of Salts

Overview

• Neutralization Reaction: Reaction between an acid and a base to form salt and water.
• Hydrolysis of Salts: Reaction of salts with water, analyzing three scenarios.

Scenario 1: Strong Acid and Strong Base

• Example: Hydrochloric acid (HCl) + Sodium hydroxide (NaOH)
• Products: Sodium chloride (NaCl) and water
• Conjugate Pairs:
  • Sodium ion (Na⁺) from NaOH: Conjugate acid (weak)
  • Chlorine ion (Cl⁻) from HCl: Conjugate base (weak)
• Hydrolysis Reaction:
  • Cl⁻ and Na⁺ are weak and do not react significantly with water.
  • No further hydrolysis reaction occurs.
• Conclusion: Salt formed (NaCl) is neutral.

Scenario 2: Strong Acid and Weak Base

• Example: Hydrochloric acid (HCl) + Ammonium hydroxide (NH₄OH)
• Products: Ammonium chloride (NH₄Cl) and water
• Conjugate Pairs:
  • Ammonium ion (NH₄⁺): Strong conjugate acid
  • Chlorine ion (Cl⁻): Weak conjugate base
• Hydrolysis Reaction:
  • NH₄⁺ donates a proton to water, forming hydronium ions (H₃O⁺) and ammonia (NH₃).
  • This indicates that NH₄Cl is acidic.
• Conclusion: Salt formed (NH₄Cl) is acidic, resulting in an acidic solution.

Scenario 3: Weak Acid and Strong Base

• Example: Acetic acid (CH₃COOH) + Sodium hydroxide (NaOH)
• Products: Sodium acetate (CH₃COONa) and water
• Conjugate Pairs:
  • Acetate ion (CH₃COO⁻): Strong conjugate base
  • Sodium ion (Na⁺): Weak conjugate acid
• Hydrolysis Reaction:
  • CH₃COO⁻ accepts a proton from water, forming hydroxide ions (OH⁻).
  • Presence of OH⁻ makes the solution more basic.
• Conclusion: Salt formed (CH₃COONa) is basic, resulting in a basic solution.

Key Takeaways

• Strong Acid + Strong Base: Neutral salt, neutral solution.
• Strong Acid + Weak Base: Acidic salt, acidic solution.
• Weak Acid + Strong Base: Basic salt, basic solution.
• Hydrolysis: Determines the nature of the salt and the resulting solution's pH.