Acidity and Basicity of Salts

Introduction

• Topic: Acidity and basicity of salts
• Instructor: Chad from Chad's Prep
• Purpose: Stress-free learning of science
• Related Prep Courses: MCAT, DAT, OAT (links in description)
• Part of General Chemistry Playlist

Key Concepts

Definition of Salts

• Salts are ionic compounds
• Different from acids (H+ with non-metals) and strong bases (Group 1 and 2 hydroxides)

Types of Salts

1. Acidic Salts
   • pH < 7 when dissolved in water
2. Basic Salts
   • pH > 7 when dissolved in water
3. Neutral Salts
   • pH = 7 when dissolved in water

Importance of Strong Acids/Bases

• Need to memorize strong acids and bases to classify salts correctly
• Cations and anions should be treated separately

Lewis Definitions

• Lewis Acid: Electron acceptor, usually cations
• Lewis Base: Electron donor, usually anions
• General rule:
  • Cations are often acidic (electron acceptors)
  • Anions are often basic (electron donors)

Anions

• Negligible Bases: Chloride, Bromide, Iodide, Nitrate, Chlorate, Perchlorate
  • Conjugate bases of strong acids; do not affect pH
• Special Case: H2SO4
  • HSO4- is a weak acid (not negligible)

Cations

• Negligible Cations: Group 1 and 2 metals
  • Transition metals with +1 charge
• Strength of Lewis Acids:
  • More positive charge = stronger acid
  • Smaller size = stronger acid

Identification of Salt Types

• Neutral Salt: Negligible cation and anion
• Acidic Salt: Acidic cation and negligible anion
• Basic Salt: Negligible cation and basic anion

Examples of Ionic Compounds

1. Magnesium Hydroxide
   • Strong base; basic salt
2. Sodium (Na+) and Barium (Ba2+)
   • Negligible cations; analyze anions for classification
3. Aluminium Perchlorate
   • Acidic salt
4. Ammonium Cyanide
   • Requires k_a and k_b values to classify

pH Calculations

Sodium Fluoride (NaF)

• Cation: Na+ (negligible)
• Anion: F- (basic)
• Expected pH: > 7
• Kb Calculation: Need to find Kb using Ka of HF

Ammonium Chloride (NH4Cl)

• Cation: NH4+ (weak acid)
• Anion: Cl- (negligible)
• Expected pH: < 7
• Ka Calculation: Need to find Ka using Kb of NH3

Challenges in Calculations

• Recognizing the type of acid/base is crucial for calculations
• Identify if you have a strong acid/base, weak acid/base, or salt to determine the appropriate method
• Importance of understanding the relationship between K_a, K_b, and K_w

Conclusion

• Mastering acidity and basicity of salts is essential
• Next chapter will cover buffers and titrations, which increase complexity
• Encouragement to practice and utilize resources available (links in description)

• If this lesson was helpful, thumbs up on the YouTube channel is appreciated
• Links for practice questions and final exam reviews in description.