Lecture on Salts

Introduction to Salts

• Commonly perceived as table salt (sodium chloride).
• Salt refers to a large family of compounds with diverse properties and uses.

Definition of a Salt

• Ionic Compound: Made up of positively charged cations and negatively charged anions.
  • Electrically neutral.
• Cation: Usually a metal, often from Group 1 or 2 of the periodic table.
• Anion: Commonly a halide from Group 7 or a member of Group 6.
• Inorganic Salts: Traditional definition but not exclusive.
• Polyatomic Ions: Made up of more than one atom (e.g., ammonium salts).

Diversity of Salts

• Appearance: Not all salts are clear crystals.
  • Sodium chromate: Yellow.
  • Potassium permanganate: Purple.
  • Iron disulfide: Shiny and metallic, aka "fool's gold."
• Taste: Not all salts taste salty.
  • Some are bitter, others sweet (e.g., lead diacetate, which is poisonous).
• Special Types:
  • Diazonium Salts: Brightly colored, used for dye pigments in clothing.
  • Fireworks: Colors produced by burning metal salts.

Chemical Reactions Involving Salts

• Acid-Base Reaction: Produces a salt and water.
  • Example: Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water.
  • Monitoring Reaction: Use pH indicator like methyl orange.
    • Methyl orange turns from orangey-red to yellow as pH rises.
    • Neutralization observed by pH change; evaporate water to collect salt crystals.
• Industrial Production: Sodium chloride mined or evaporated from seawater.

Alternative Methods of Making Salts

• Metal and Acid Reaction.
• Metal and Non-metal Combination (e.g., metal and halogen).

Solubility of Salts

• Water Solubility:
  • Salts with sodium, potassium, ammonium cations, and nitrate anions are water soluble.
  • Carbonate anion salts are often water insoluble.
• Insoluble and Sparingly Soluble Salts:
  • Some salts dissolve slightly, leaving crystals.

Properties of Salts in Solution

• Electrolytes: Conduct electricity when dissolved in solution.