Making Insoluble Salts

• Insoluble compounds cannot be made by reacting acids with insoluble bases or carbonates due to the formation of an impervious coat.

• To create an insoluble compound, mix two solutions leading to a precipitate.

Choosing Solutions

• Identify the Bivalent Cation:

  • Look at the first part of the name of the insoluble compound.

• Identify the Anion:

  • Look at the second part of the name.

• Select solutions containing these ions.

Examples of Making Insoluble Compounds

• Lead Sulfate (White Precipitate):

  • Use Lead Nitrate and Sodium Sulfate.

  • Equation:
    $\text{Lead nitrate} + \text{Sodium sulfate} \rightarrow \text{Lead sulfate} + \text{Sodium nitrate}$

• Lead Iodide (Yellow Precipitate):

  • Use Lead Nitrate and Potassium Iodide.

  • Equation:
    $\text{Lead nitrate} + \text{Potassium iodide} \rightarrow \text{Lead iodide} + \text{Potassium nitrate}$

• Aluminium Hydroxide (White Precipitate):

  • Use Aluminium Sulfate and Sodium Hydroxide.

  • Equation:
    $\text{Aluminium sulfate} + \text{Sodium hydroxide} \rightarrow \text{Aluminium hydroxide} + \text{Sodium sulfate}$

Purification of Insoluble Compounds

• Filter the mixture to collect the residue (the precipitate).

• Rinse the residue on filter paper with distilled water to remove soluble impurities.

• Dry the residue in an oven at 50°C.