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Starting with solid calcium nitrate, describe how a pure dry sample of calcium carbonate can be prepared in the laboratory

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To prepare a pure dry sample of calcium carbonate (\( \text{CaCO}_3 \)) starting with solid calcium nitrate (\( \text{Ca(NO}_3\text{)}_2 \)), you can follow these steps:

Materials Needed:

  1. Solid calcium nitrate (\( \text{Ca(NO}_3\text{)}_2 \))
  2. A source of carbonate ions (e.g., sodium carbonate (\( \text{Na}_2\text{CO}_3 \)) or sodium bicarbonate (\( \text{NaHCO}_3 \)))
  3. Distilled water
  4. Beaker
  5. Stirring rod
  6. Filter paper and funnel
  7. Evaporating dish
  8. Heat source (optional, if evaporation of water is needed)

Procedure:

  1. Dissolve Calcium Nitrate:

    • Measure an appropriate amount of solid calcium nitrate and dissolve it in distilled water in a beaker to make a saturated solution. Stir the solution with a stirring rod until all the solid has dissolved.

  2. Add Carbonate Source:

    • In a separate container, prepare a solution of sodium carbonate or sodium bicarbonate in distilled water. Choose sodium carbonate for a more direct reaction (as it produces carbonate ions directly).
    • Slowly add the carbonate solution to the calcium nitrate solution while stirring continuously. This will cause a double displacement reaction to take place: \[ \text{Ca(NO}_3\text{)}_2 (aq) + \text{Na}_2\text{CO}_3 (aq) \rightarrow \text{CaCO}_3 (s) + 2\text{NaNO}_3 (aq) \]
    • As the reaction occurs, white precipitate of calcium carbonate (\( \text{CaCO}_3 \)) will form.

  3. Filter the Precipitate:

    • Once the precipitate has formed, it can be collected by filtration. Set up a funnel with filter paper and pour the mixture through the filter. The calcium carbonate will remain on the filter paper while the sodium nitrate solution will pass through.

  4. Wash the Precipitate:

    • Rinse the collected calcium carbonate on the filter paper with distilled water to remove any soluble impurities (sodium nitrate).

  5. Dry the Precipitate:

    • Transfer the washed calcium carbonate to an evaporating dish. Either allow it to air dry or gently heat it to remove any remaining water. Be careful not to overheat, as \( \text{CaCO}_3 \) can decompose at higher temperatures.

  6. Collect the Dry Product:

    • Once dried, collect the pure dry sample of calcium carbonate.

Notes:

  • Ensure that the calcium nitrate and carbonate sources are of high purity to avoid contamination.
  • It is important to perform this procedure in a well-ventilated area or under a fume hood, especially during the heating stage, to avoid inhaling any fumes.
  • Keep in mind that calcium carbonate can also form in different crystal forms (calcite, aragonite) based on the conditions of the reaction and crystallization.

By following these steps, you will successfully prepare a pure dry sample of calcium carbonate in the laboratory.