Problem 57 - Introductory Chemistry Atoms First

Question

Suppose you had oxalic acid, \(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\), and you wanted to make sodium oxalate, \(\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4} .\) How might you do this?

Step-by-Step Solution

Answer

To convert oxalic acid (H₂C₂O₄) into sodium oxalate (Na₂C₂O₄), follow these steps: 1. Write the balanced chemical equation: \(H_{2}C_{2}O_{4} + 2NaOH \rightarrow Na_{2}C_{2}O_{4} + 2H_{2}O\). 2. Obtain the reactants, oxalic acid (H₂C₂O₄) and sodium hydroxide (NaOH). 3. Prepare separate solutions of oxalic acid and sodium hydroxide by dissolving the solids in distilled water. 4. Slowly add the sodium hydroxide solution to the oxalic acid solution, stirring continuously. 5. Allow the mixture to stand undisturbed, letting the sodium oxalate precipitate at the bottom of the container. 6. Filter the solution to isolate the solid sodium oxalate, rinsing it with distilled water to remove any remaining impurities. 7. Dry the sodium oxalate on a watch glass or use a gentle heat source to speed up the drying process, then store it in an appropriate container.

Step 1: Write the balanced chemical equation

First, we need to write the balanced chemical equation for the conversion of oxalic acid to sodium oxalate. The balanced chemical equation is: \(H_{2}C_{2}O_{4} + 2NaOH \rightarrow Na_{2}C_{2}O_{4} + 2H_{2}O\) In this reaction, oxalic acid reacts with sodium hydroxide (NaOH) to form sodium oxalate and water.

Step 2: Obtain the reactants

In order to perform this reaction, we need to obtain the reactants, which are oxalic acid (H₂C₂O₄) and sodium hydroxide (NaOH). Oxalic acid is a white crystalline solid, while sodium hydroxide can be obtained in the form of pellets or flakes.

Step 3: Prepare a solution of oxalic acid

To prepare a solution of oxalic acid, weigh out an appropriate amount of the solid and dissolve it in a known volume of distilled water. It's important to use a suitable container (such as a beaker or a flask) and a stirring rod to help the oxalic acid dissolve.

Step 4: Prepare a solution of sodium hydroxide

Similar to the preparation of the oxalic acid solution, weigh out an appropriate amount of sodium hydroxide and dissolve it in a separate container with distilled water. Take care when working with sodium hydroxide, as it is highly caustic and can cause severe burns; always wear appropriate protective gear (e.g., gloves, goggles).

Step 5: Combine the solutions

Slowly add the sodium hydroxide solution to the container holding the oxalic acid solution, while continuously stirring the mixture. The reaction will produce sodium oxalate (Na₂C₂O₄) and water (H₂O) as the end products. It is critical to add the sodium hydroxide solution slowly to prevent any sudden heat release and unwanted reactions.

Step 6: Let the sodium oxalate precipitate

After combining the solutions, allow the mixture to stand undisturbed. Sodium oxalate will gradually precipitate (form solid crystals) at the bottom of the container.

Step 7: Isolate the sodium oxalate

Once the sodium oxalate has fully precipitated, carefully filter the solution through a Buchner funnel to separate the solid sodium oxalate from the liquid. Make sure to rinse the solid with distilled water to remove any remaining impurities.

Step 8: Dry the sodium oxalate

Finally, place the isolated sodium oxalate on a watch glass to air dry or use a gentle heat source (e.g., a hot plate) to speed up the drying process. Once completely dry, the sodium oxalate can be stored in an appropriate container for future use.

Key Concepts

Oxalic Acid

Oxalic acid is a naturally occurring organic compound with the formula \( \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \). It's commonly found in many plants, including spinach and rhubarb.
It appears as a white crystalline solid and is known for its role in various chemical processes.

• Physical Properties: Oxalic acid has a melting point of about 189.5 °C (373.1 °F).
• Uses: It's used in cleaning and bleaching applications because of its ability to act as a reducing agent.

Oxalic acid is relatively strong among organic acids, meaning it can effectively donate protons to other compounds. This property is crucial in its reactions, including its interaction with sodium hydroxide to form sodium oxalate.

Sodium Hydroxide

Sodium hydroxide, often known as caustic soda or lye, is another critical reactant in the formation of sodium oxalate.
Its chemical formula is \( \mathrm{NaOH} \), and it is a highly caustic base and alkali.

• Physical Properties: Sodium hydroxide is a white solid that absorbs moisture from the air and is typically available as pellets or flakes.
• Safety Precautions: Due to its corrosive nature, handle sodium hydroxide with care, using protective equipment like gloves and goggles.
• Applications: It is widely used in the manufacture of soaps, detergents, and paper.

Upon dissolving in water, sodium hydroxide dissociates completely to provide hydroxide ions, making it an excellent candidate for neutralizing acids in reactions like forming sodium oxalate.

Sodium Oxalate

The final product of the reaction between oxalic acid and sodium hydroxide is sodium oxalate with the chemical formula \( \mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \). This compound forms as a precipitate when the two solutions are mixed.

• Chemical Properties: Sodium oxalate is insoluble in water, which makes it easy to separate from the reaction mixture.
• Uses: It is used in analytical chemistry and has applications in the field of electroplating and as a reducing agent.

As it forms from the reaction, sodium oxalate precipitates out of solution which can then be isolated through filtration for further use.

Chemical Equation

A chemical equation represents a chemical reaction, showcasing the reactants undergoing change to form products.
The equation for this particular reaction is:\[ \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} + 2 \mathrm{NaOH} \rightarrow \mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4} + 2 \mathrm{H}_{2} \mathrm{O} \]In this reaction:

• Reactants: Oxalic acid and sodium hydroxide react to produce.
• Products: The main products are sodium oxalate and water.

Balancing the chemical equation is crucial because it ensures that the number of atoms for each element is conserved during the reaction, complying with the law of conservation of mass.

Reaction Stoichiometry

Reaction stoichiometry involves the calculation of the relationships between reactants and products in a chemical reaction.
It uses the coefficients of the balanced chemical equation to ensure the correct proportions.

• Molecular Proportions: In the balanced equation \( \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} + 2 \mathrm{NaOH} \rightarrow \mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4} + 2 \mathrm{H}_{2} \mathrm{O} \), each mole of oxalic acid reacts with two moles of sodium hydroxide.
• Importance: Stoichiometry is vital for predicting the amounts of products generated and for optimizing the efficiency of the reaction.

Understanding stoichiometry is essential for ensuring that all reactants fully convert to the products desired, which is particularly important in industrial and laboratory chemical synthesis.