Question

Describe how you would prepare (a) cadmium(II) carbonate from a solution of cadmium(II) nitrate. (b) copper(II) hydroxide from a solution of sodium hydroxide. (c) magnesium carbonate from a solution of magnesium chloride.

Short answer

Answer: The steps to prepare cadmium(II) carbonate from a solution of cadmium(II) nitrate are: 1. Prepare a solution of cadmium(II) nitrate by dissolving the required amount in deionized water. 2. Prepare a solution of sodium carbonate by dissolving the required amount in deionized water. 3. Slowly add the sodium carbonate solution to the cadmium nitrate solution with stirring, resulting in the formation of a white precipitate of cadmium carbonate. 4. Allow the precipitate to settle at the bottom of the container and separate the solid cadmium carbonate by decanting the supernatant liquid or using filtration. 5. Thoroughly wash the cadmium carbonate precipitate with deionized water to remove any remaining sodium nitrate and allow it to dry before use.

Step-by-step solution

(a) Preparing cadmium(II) carbonate from a solution of cadmium(II) nitrate

First, we need to write the chemical reaction between cadmium nitrate and a suitable compound that will produce cadmium carbonate as a precipitate. In this case, we can use sodium carbonate as the reagent: Cd(NO3)2 (aq) + Na2CO3 (aq) -> CdCO3 (s) + 2NaNO3 (aq) Follow these steps to prepare cadmium(II) carbonate: Step 1: Prepare a solution of cadmium(II) nitrate, by dissolving the required amount in deionized water. Step 2: Prepare a solution of sodium carbonate by dissolving the required amount in deionized water. Step 3: Slowly add the sodium carbonate solution to the cadmium nitrate solution with stirring. The reaction between the two solutions will result in the formation of a white precipitate, which is cadmium carbonate. Step 4: Allow the precipitate to settle at the bottom of the container. Decant the supernatant liquid or use filtration to separate the solid cadmium carbonate. Step 5: Thoroughly wash the cadmium carbonate precipitate with deionized water to remove any remaining sodium nitrate. Allow it to dry before use.

(b) Preparing copper(II) hydroxide from a solution of sodium hydroxide

First, we need to find a suitable compound to react with sodium hydroxide to produce copper(II) hydroxide as a precipitate. In this case, we can use copper(II) sulfate as the reagent: 2NaOH (aq) + CuSO4 (aq) -> Cu(OH)2 (s) + Na2SO4 (aq) Follow these steps to prepare copper(II) hydroxide: Step 1: Prepare a solution of sodium hydroxide by dissolving the required amount in deionized water. Step 2: Prepare a solution of copper(II) sulfate by dissolving a suitable amount in deionized water. Step 3: Slowly add the sodium hydroxide solution to the copper(II) sulfate solution, with stirring. A blue precipitate of copper(II) hydroxide will form. Step 4: Allow the precipitate to settle at the bottom of the container, then decant the supernatant liquid or use filtration to separate the solid copper(II) hydroxide. Step 5: Thoroughly wash the copper(II) hydroxide precipitate with deionized water to remove any remaining sodium sulfate. Allow it to dry before use.

(c) Preparing magnesium carbonate from a solution of magnesium chloride

To prepare magnesium carbonate, we need to react magnesium chloride with a compound that will produce magnesium carbonate as a precipitate. In this case, we can use sodium carbonate as the reagent: MgCl2 (aq) + Na2CO3 (aq) -> MgCO3 (s) + 2NaCl (aq) Follow these steps to prepare magnesium carbonate: Step 1: Prepare a solution of magnesium chloride by dissolving the required amount in deionized water. Step 2: Prepare a solution of sodium carbonate by dissolving the required amount in deionized water. Step 3: Slowly add the sodium carbonate solution to the magnesium chloride solution, with stirring. A white precipitate of magnesium carbonate will form. Step 4: Allow the precipitate to settle at the bottom of the container, then decant the supernatant liquid or use filtration to separate the solid magnesium carbonate. Step 5: Thoroughly wash the magnesium carbonate precipitate with deionized water to remove any remaining sodium chloride. Allow it to dry before use.

Key concepts

Cadmium(II) Carbonate Preparation

When it comes to creating compounds like cadmium(II) carbonate in the lab, understanding the process of chemical precipitation is crucial. Precipitation reactions involve combining aqueous solutions of different ions to form a new substance that is insoluble in water, causing it to settle out as a solid.

For the preparation of cadmium(II) carbonate, cadmium(II) nitrate and sodium carbonate are the reactants that undergo a double displacement reaction. When mixed, they produce cadmium carbonate, a white precipitate, and sodium nitrate, which remains in solution. The balanced chemical equation for this process is:
\[ Cd(NO_3)_2 (aq) + Na_2CO_3 (aq) \rightarrow CdCO_3 (s) + 2NaNO_3 (aq) \]

It is important to control the reaction conditions to ensure that a pure product is obtained. By slowly mixing the solutions and constant stirring, a complete reaction is encouraged, maximizing yield. Once the precipitate forms, it is crucial to remove the soluble impurities such as sodium nitrate by washing the cadmium carbonate with deionized water. Finally, drying the precipitate ensures that it is ready for further use or study.

Copper(II) Hydroxide Synthesis

Similarly, synthesizing copper(II) hydroxide employs a precipitation reaction between sodium hydroxide, a common base, and copper(II) sulfate. The result of this reaction is a distinctive blue precipitate of copper(II) hydroxide and a by-product of sodium sulfate in the solution. The chemical equation representing this synthesis is:
\[ 2NaOH (aq) + CuSO_4 (aq) \rightarrow Cu(OH)_2 (s) + Na_2SO_4 (aq) \]

The practical steps for copper(II) hydroxide production require careful addition of the sodium hydroxide solution to a copper(II) sulfate solution. Precipitation reactions are exothermic, so it's important to control the addition rate to manage the temperature and avoid unwanted side reactions. Students should note that the purity of the final product can be compromised by the incomplete washing of the precipitate. Ensuring thorough washing and proper drying is essential to obtain a sample of copper(II) hydroxide ready for application or further analytical procedures.

Magnesium Carbonate Production

Producing magnesium carbonate follows a approach analogous to the previous syntheses. The interaction between magnesium chloride and sodium carbonate in aqueous solution results in the formation of a white precipitate of magnesium carbonate and soluble sodium chloride. The chemical formula for this precipitation reaction is as follows:
\[ MgCl_2 (aq) + Na_2CO_3 (aq) \rightarrow MgCO_3 (s) + 2NaCl (aq) \]

The correct execution of this method consists of preparing and mixing the solutions, slowly combining them to form the precipitate, and then isolating it using filtration or decantation. Just as with the other compounds, the purity of the magnesium carbonate is critical; it must be washed to remove the sodium chloride. After allowing it to dry, the magnesium carbonate can be used for various applications ranging from industrial to pharmaceutical. It's essential to maintain optimal conditions throughout the procedure to ensure the highest yield and purity of the final product.