Question

Oxalic acid is heated with concentrated \(\mathrm{H}_{2} \mathrm{SO}_{4} .\) when the resultant gases are passed over red hot carbon, \(\mathrm{X}\) is obtained. X, is: (a) \(\mathrm{CO}\) (b) \(\mathrm{CO}_{2}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{4}\) (d) \(\mathrm{CH}_{4}\)

Short answer

X is (a) \( \mathrm{CO} \).

Step-by-step solution

Understand the Problem

We need to determine which gas, designated as \( \mathrm{X} \), is produced when oxalic acid is heated with concentrated \( \mathrm{H}_{2} \mathrm{SO}_{4} \) and the gases are passed over red hot carbon.

Identify the Reaction with Concentrated Sulfuric Acid

When oxalic acid \( (\mathrm{H}_2\mathrm{C}_2\mathrm{O}_4) \) is heated with concentrated sulfuric acid \( (\mathrm{H}_2\mathrm{SO}_4) \), it decomposes to produce carbon monoxide \( (\mathrm{CO}) \), carbon dioxide \( (\mathrm{CO}_2) \), and water vapor \( (\mathrm{H}_2\mathrm{O}) \). The relevant reaction can be written as:\[ \mathrm{H}_2\mathrm{C}_2\mathrm{O}_4 \rightarrow \mathrm{CO} + \mathrm{CO}_2 + \mathrm{H}_2\mathrm{O} \]

Reaction Over Red Hot Carbon

The gases produced, \( \mathrm{CO} \) and \( \mathrm{CO}_2 \), are passed over red hot carbon. Over red hot carbon, \( \mathrm{CO}_2 \) undergoes the following reaction:\[ \mathrm{CO}_2 + \mathrm{C} \rightarrow 2\mathrm{CO} \]This means that any \( \mathrm{CO}_2 \) is converted into \( \mathrm{CO} \), resulting in an increase in the amount of \( \mathrm{CO} \).

Conclusion on Gas X

As a result of the reactions, the gas \( \mathrm{X} \) obtained is predominantly carbon monoxide \( (\mathrm{CO}) \) because the \( \mathrm{CO}_2 \) is converted into \( \mathrm{CO} \) over red hot carbon. Therefore, \( \mathrm{X} \) is \( \mathrm{CO} \).

Key concepts

Oxalic Acid

Oxalic acid, a relatively simple organic compound, is represented by the formula \( \mathrm{H}_2\mathrm{C}_2\mathrm{O}_4 \). It's naturally found in many plants, such as spinach and rhubarb, giving them a slightly tart taste. Oxalic acid plays an essential role in different chemical processes; however, it needs to be handled with care as it can be toxic when ingested in large amounts.
When oxalic acid is heated, interesting chemical reactions occur. It decomposes, breaking down into smaller elements including water vapor \( \mathrm{H}_2\mathrm{O} \), carbon monoxide \( \mathrm{CO} \), and carbon dioxide \( \mathrm{CO}_2 \). This decomposition process is crucial because it forms the basis for other reactions, especially when involved with substances like sulfuric acid.

Carbon Monoxide

Carbon monoxide \( (\mathrm{CO}) \) is a colorless, odorless gas that results from incomplete combustion. In the context of oxalic acid decomposition, it is one of the products generated when oxalic acid is heated.
Carbon monoxide plays a significant role in this scenario. When the gases produced from heated oxalic acid are passed over red hot carbon, \( \mathrm{CO_2} \) reacts to form additional \( \mathrm{CO} \). This reaction enhances the amount of carbon monoxide present, making it the dominant compound. Although abundant in controlled reactions and industrial processes, carbon monoxide is infamous for being a "silent killer" due to its toxic effects on the human body, which is why handling it safely is imperative.

Sulfuric Acid

Sulfuric acid \( (\mathrm{H}_2\mathrm{SO}_4) \) is one of the most potent acids widely used in industrial and laboratory settings. Known for its ability to dehydrate substances by removing water, it plays a key role in the breakdown of compounds like oxalic acid.
When concentrated sulfuric acid is heated with oxalic acid, it catalyzes the decomposition of oxalic acid into carbon monoxide, carbon dioxide, and water vapor. This is because sulfuric acid aids in removing the components of oxalic acid, facilitating their breakdown at a faster rate. Its effectiveness in driving the reaction showcases its energetic nature and reactive capabilities.

Red Hot Carbon

Red hot carbon refers to carbon that has been heated to high temperatures. At such a state, carbon becomes highly reactive, making it a powerful agent in facilitating chemical reactions.
In the scenario we are exploring, red hot carbon plays a pivotal role in converting \( \mathrm{CO_2} \) into additional carbon monoxide \( \mathrm{CO} \). This is because the elevated temperature of the carbon provides enough energy for reactions that would otherwise not occur at lower temperatures. The equation \( \mathrm{CO}_2 + \mathrm{C} \rightarrow 2\mathrm{CO} \) highlights this transformation. The presence of red hot carbon ensures that the \( \mathrm{CO} \) levels increase significantly, leading to the dominance of carbon monoxide as a product.