Lecture Notes: Making and Isolating Insoluble Salts

Introduction

• Some salts are soluble in water, while others are insoluble.
• Previously learned about making and isolating soluble salts.
• Focus of this lesson: Making and isolating insoluble salts.

Precipitation Method

• Example: Sodium iodide (NaI) and silver nitrate (AgNO₃) are soluble in water, forming aqueous solutions.

  • Add silver nitrate dropwise to sodium iodide.
  • A bright yellow solid (precipitate) is formed.
  • The reaction is a double displacement reaction:
    • Sodium ion (Na⁺) and silver ion (Ag⁺) switch places.
    • Products: Silver iodide (AgI) and sodium nitrate (NaNO₃).

• Representing Reactions:

  • Soluble salts in water: Represented with (aq) for aqueous.
  • Insoluble precipitate: Represented with (s) for solid.

Identifying the Precipitate

• Use the solubility table to determine the precipitate.

  • Nitrate salts are generally soluble in water.
  • Iodide salts are soluble, except with lead and silver.

• Result:

  • Silver iodide (AgI) is insoluble; hence, it is the precipitate.

Isolating the Precipitate

• Filtration Process:
  • Filter the mixture through a funnel lined with filter paper.
  • Rinse with distilled water to collect all precipitate.
  • The solid collected is the residue; the liquid is the filtrate.

Challenge

• Reaction Prediction: Predict products for barium chloride (BaCl₂) and potassium sulfate (K₂SO₄).

  • Balance the reaction equation and include state symbols.

• Solution:

  • Potassium chloride (KCl) is aqueous.
  • Barium sulfate (BaSO₄) is the insoluble precipitate.
  • Barium sulfate is used in medical imaging as it is not absorbed by the body.

Methods of Forming Insoluble Salts

• Precipitation Method: Using soluble solutions to form an insoluble precipitate.
• Direct Combination: Combining constituent elements.

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Key Points:

• Understanding solubility rules is crucial for identifying precipitates.
• Filtration is a key technique to isolate and collect precipitates.
• Insoluble salts have practical applications, such as in medical imaging.

Important Terms:

• Precipitate: An insoluble solid formed from a solution.
• Residue: Solid collected after filtration.
• Filtrate: Liquid separated from the solid during filtration.