Lecture on Soluble and Insoluble Salts

Introduction

• Some salts are soluble in water; some are insoluble.
• Previous lesson: Making and isolating soluble salts.
• Current lesson: Making and isolating insoluble salts.

Precipitation Method

• Example Reaction: Sodium iodide (NaI) and silver nitrate (AgNO₃)
  • Both form aqueous solutions (soluble in water).
  • Combining them results in a bright yellow solid (precipitate).
  • Reaction Type: Double displacement reaction.
    • Sodium ion (Na⁺) and silver ion (Ag⁺) switch places.
  • Products: Silver iodide (AgI) and sodium nitrate (NaNO₃).
  • State Symbols:
    • Aqueous solutions denoted by (aq).
    • Precipitate denoted by (s).

Identifying the Precipitate

• Use the solubility table:
  • All nitrate salts are soluble in water.
  • Most iodide salts are soluble except with lead and silver.
• Result: Silver iodide (AgI) is the precipitate (insoluble).

Isolation of Precipitate

• Method: Filtration
  • Use filter paper and funnel.
  • Rinse with distilled water to collect all precipitate.
  • Definitions:
    • Residue: Collected solid.
    • Filtrate: Liquid separated from the solid.

Challenge Problem

• Reaction: Barium chloride (BaCl₂) and potassium sulfate (K₂SO₄).
• Predict products using solubility rules.
  • Chloride salts generally soluble.
  • Sulfate salts mostly soluble except for some like barium sulfate (BaSO₄).
• Balanced Reaction Equation
  • Barium sulfate forms as an insoluble precipitate.

Applications of Insoluble Salts

• Barium sulfate as a contrast agent for x-rays.

Alternative Method for Insoluble Salt Formation

• Direct Combination: Combine constituent elements directly.

Summary

• Two methods to form insoluble salts:
  1. Precipitation.
  2. Direct combination.