Problem 131 - Chemistry The Molecular Science

Question

Explain how you could prepare barium sulfate by (a) an acid-base reaction, (b) a precipitation reaction, and (c) a gas-forming reaction. The materials you have to start with are \(\mathrm{BaCO}_{3}, \mathrm{Ba}(\mathrm{OH})_{2}, \mathrm{Na}_{2} \mathrm{SO}_{4},\) and \(\mathrm{H}_{2} \mathrm{SO}_{4}\) .

Step-by-Step Solution

Answer

Combine barium hydroxide or carbonate with sulfuric acid or sodium sulfate to form barium sulfate.

Step 1: Acid-Base Reaction

To prepare barium sulfate using an acid-base reaction, we can react barium hydroxide, \( \mathrm{Ba(OH)}_2 \), with sulfuric acid, \( \mathrm{H}_2\mathrm{SO}_4 \). This will result in the formation of barium sulfate and water:\[ \mathrm{Ba(OH)}_2 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + 2 \mathrm{H}_2\mathrm{O}.\]Barium sulfate, \(\mathrm{BaSO}_4\), is insoluble in water and will precipitate out of solution.

Step 2: Precipitation Reaction

For a precipitation reaction, we can mix barium hydroxide, \(\mathrm{Ba(OH)}_2\), or barium carbonate, \(\mathrm{BaCO}_3\), with \(\mathrm{Na}_2\mathrm{SO}_4\) in aqueous solution. We will use \(\mathrm{Na}_2\mathrm{SO}_4\) here:\[ \mathrm{Ba(OH)}_2 + \mathrm{Na}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + 2\mathrm{NaOH} \]The barium sulfate, \(\mathrm{BaSO}_4\), will again precipitate, as it is insoluble in water.

Step 3: Gas-Forming Reaction

In a gas-forming reaction, \(\mathrm{BaCO}_3\) can react with \(\mathrm{H}_2\mathrm{SO}_4\), resulting in the evolution of carbon dioxide gas and the formation of barium sulfate and water:\[ \mathrm{BaCO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2 \uparrow\]The release of \(\mathrm{CO}_2\) gas indicates the reaction, and \(\mathrm{BaSO}_4\) forms as an insoluble solid.

Key Concepts

Acid-Base Reaction

An acid-base reaction is a fundamental chemical process where an acid reacts with a base to produce water and a salt. In our scenario, we mix barium hydroxide, \( \mathrm{Ba(OH)}_2 \), a base, with sulfuric acid, \( \mathrm{H}_2\mathrm{SO}_4 \), an acid. This combination yields the insoluble compound barium sulfate, \( \mathrm{BaSO}_4 \), along with water.The reaction can be summarized as follows:\[ \mathrm{Ba(OH)}_2 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + 2 \mathrm{H}_2\mathrm{O} \]Barium sulfate precipitates out of solution because it is not soluble in water, making it easy to separate from the liquid mixture. This characteristic is useful in various industrial and medical applications, where barium sulfate finds use due to its chemical inertness and opacity to X-rays.
Understanding acid-base reactions helps in predicting outcomes when acids and bases are mixed, a crucial aspect in fields like chemistry and medicine.

Precipitation Reaction

Precipitation reactions occur when two aqueous solutions combine to form an insoluble salt, known as a precipitate. This type of reaction is highly valuable in isolation and purification processes.

For preparing barium sulfate, a precipitation reaction involves mixing barium hydroxide (\( \mathrm{Ba(OH)}_2 \)) with sodium sulfate (\( \mathrm{Na}_2\mathrm{SO}_4 \)). The chemical equation for this reaction is:\[ \mathrm{Ba(OH)}_2 + \mathrm{Na}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + 2\mathrm{NaOH} \]Barium sulfate will appear as a solid precipitate because of its very low solubility in water. Precipitation reactions are pivotal for laboratory and industrial processes where specific compounds need to be extracted or removed from a solution. The visual clue of a solid formation in liquid can be fascinating, showing a direct transformation that helps in identifying the reaction's completion.

Gas-Forming Reaction

Gas-forming reactions are intriguing because they produce a gaseous byproduct, often making the reaction visible and dynamic. Here, when barium carbonate (\( \mathrm{BaCO}_3 \)) reacts with sulfuric acid (\( \mathrm{H}_2\mathrm{SO}_4 \)), it not only forms barium sulfate but also releases carbon dioxide gas. The equation for the gas-forming reaction is:\[ \mathrm{BaCO}_3 + \mathrm{H}_2\mathrm{SO}_4 \rightarrow \mathrm{BaSO}_4 + \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2 \uparrow \]The carbon dioxide gas evolution is an observable phenomenon that serves as an indicator of the reaction's occurrence. Meanwhile, barium sulfate, being insoluble, will precipitate. This type of reaction is used in applications such as CO2 production for industrial purposes and serves educational purposes in illustrating reaction evidence visually.
Understanding gas-forming reactions helps in grasping concepts related to chemical kinetics and dynamic system visualizations.