Making and Isolating Insoluble Salts

Key Concepts

• Some salts are soluble in water, while others are insoluble.
• This lesson focuses on the formation and isolation of insoluble salts.

Precipitation Method

• Example: Sodium iodide + Silver nitrate
  • Both salts are soluble, forming aqueous solutions.
  • Reaction: Add silver nitrate dropwise to sodium iodide.
  • Observation: Formation of a bright yellow solid (precipitate).
  • Definition: A precipitate is an insoluble solid formed from the reaction of two solutions.
  • Type of Reaction: Double displacement reaction, where ions switch places.
  • Products: Silver iodide (insoluble) and Sodium nitrate (soluble).
  • State Symbols:
    • Aqueous solutions: (aq)
    • Solid precipitate: (s)

Identifying the Precipitate

• Reference: Use the solubility table.
• **Solubility Rules: **
  • All nitrate salts are soluble in water.
  • All iodide salts are soluble, except when combined with lead and silver.
• Conclusion: Silver iodide is the insoluble precipitate, represented as (s) in the equation.

Isolating the Precipitate

• Method: Filtration through a funnel lined with filter paper.
  • Step: Rinse with distilled water to ensure all precipitate is collected.
  • Terms:
    • Residue: The solid collected.
    • Filtrate: The liquid separated from the solid.

Challenge Example

• Task: Predict the products for the reaction between barium chloride and potassium sulfate.
  • Solubility Rules:
    • Most chloride salts are soluble (potassium chloride forms an aqueous solution).
    • Most sulfate salts are soluble, except for barium sulfate (forms a precipitate).
• Reaction Equation: Include all state symbols and balance the equation.
  • Products: Barium sulfate (precipitate) and Potassium chloride (aqueous).

Real-World Application

• Barium Sulfate:
  • So insoluble it can be ingested and safely pass through the gastrointestinal tract.
  • Used as a contrast agent in x-ray imaging.

Methods to Form Insoluble Salts

• Two Methods:
  1. Precipitation
  2. Direct combination of constituent elements