Question

\(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \longrightarrow\) Gas \((\mathrm{P})+\operatorname{gas}(\mathrm{Q})+\) liquid \((\mathrm{R})\) Gas (P) burns with a blue flame and is oxidized to \(\operatorname{gas}(\mathrm{Q}) .\) Gas \((\mathrm{P})+\mathrm{Cl}_{2} \rightarrow(\mathrm{S}) \stackrel{\mathrm{NH}_{3} \Delta}{\longrightarrow}(\mathrm{T})\) (P), (Q), (R) and (T) are respectively (a) \(\mathrm{CO}, \mathrm{CO}_{2}, \mathrm{COCl}_{2}, \mathrm{HCONH}_{2}\) (b) \(\mathrm{CO}, \mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{COCl}_{2}\) (c) \(\mathrm{CO}_{2}, \mathrm{CO}, \mathrm{H}_{2} \mathrm{O}, \mathrm{HCONH}_{2}\) (d) \(\mathrm{CO}, \mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{NH}_{2} \mathrm{CONH}_{2}\)

Short answer

Option (a): \(\mathrm{CO}, \mathrm{CO}_2, \mathrm{COCl}_2, \mathrm{HCONH}_2\).

Step-by-step solution

Identify Potential Reaction Products

The decomposition of oxalic acid, \(\mathrm{H}_2\mathrm{C}_2\mathrm{O}_4\), typically results in the formation of gases and water. When heated, it often decomposes to form carbon monoxide \((\mathrm{CO})\), carbon dioxide \((\mathrm{CO}_2)\), and water \((\mathrm{H}_2\mathrm{O})\). These are the plausible products for \(\mathrm{P}\), \(\mathrm{Q}\), and \(\mathrm{R}\) respectively.

Analyze Combustion of Gas (P)

Gas \((\mathrm{P})\), which is carbon monoxide \((\mathrm{CO})\), burns with a blue flame when it reacts with oxygen, forming carbon dioxide \((\mathrm{CO}_2)\). This aligns with the description in the problem where gas \(\mathrm{P}\) is oxidized to gas \(\mathrm{Q}\). Thus, gas \(\mathrm{P}\) is \(\mathrm{CO}\) and gas \(\mathrm{Q}\) is \(\mathrm{CO}_2\).

Verify Liquid (R) Identification

Liquid \((\mathrm{R})\) is water \((\mathrm{H}_2\mathrm{O})\) produced from the decomposition of oxalic acid. This is consistent as water remains a liquid under standard conditions when produced from such decomposition reactions.

Examine Reaction Sequence for (S) and (T)

Gas \((\mathrm{P})\), \(\mathrm{CO}\), reacts with \(\mathrm{Cl}_2\) to form \(\mathrm{COCl}_2\) (phosgene) which, in reaction with \(\mathrm{NH}_3\) upon heating, produces \(\mathrm{HCONH}_2\) (formamide). Therefore, (T) is \(\mathrm{HCONH}_2\).

Match Against Options

Comparing our findings from the steps: (P) is \(\mathrm{CO}\), (Q) is \(\mathrm{CO}_2\), (R) is \(\mathrm{H}_2\mathrm{O}\), and (T) is \(\mathrm{HCONH}_2\). This matches option (a): \(\mathrm{CO}, \mathrm{CO}_2, \mathrm{COCl}_2, \mathrm{HCONH}_2\).

Key concepts

Oxalic Acid Decomposition

Oxalic acid, known chemically as \( \mathrm{H}_2\mathrm{C}_2\mathrm{O}_4 \), is an interesting compound due to its ability to decompose into gases and liquid. When subjected to heat, it breaks down into carbon monoxide \( (\mathrm{CO}) \), carbon dioxide \( (\mathrm{CO}_2) \), and water \( (\mathrm{H}_2\mathrm{O}) \). This decomposition is crucial in understanding many simple organic reactions.

• Carbon monoxide \( (\mathrm{CO}) \): A colorless, odorless gas that can burn, creating carbon dioxide.
• Carbon dioxide \( (\mathrm{CO}_2) \): A non-flammable, odorless gas, often found in combustion products.
• Water \( (\mathrm{H}_2\mathrm{O}) \): A simple liquid formed as product many decomposition reactions.

Understanding this decomposition can help grasp other reactions involving similar simple organic compounds.

Combustion Reactions

Combustion is a fascinating chemical process where a substance combines with oxygen, producing heat and light. In the case of carbon monoxide, \(\mathrm{CO}\), a combustion reaction involves its oxidation to carbon dioxide \(\mathrm{CO}_2\). This reaction is characterized by:\

• Blue Flame: This occurs due to the process of carbon monoxide burning in the presence of oxygen.
• Oxidation: Carbon monoxide gains oxygen atoms to become carbon dioxide.

These characteristics illustrate why combustion reactions are crucial in understanding chemical processes. They highlight how potentially harmful gases, like CO, can be converted into less harmful substances.

Chemical Reaction Products

Every chemical reaction results in the formation of products from reactants. The decomposition of oxalic acid clearly shows this, resulting in carbon monoxide, carbon dioxide, and water. Recognizing these products not only helps in predicting the outcomes of similar reactions but also in understanding natural processes.

• Carbon Monoxide (\(\mathrm{CO}\)): Often a reactant in further chemical reactions, such as combustion.
• Carbon Dioxide (\(\mathrm{CO}_2\)): Commonly found in numerous reactions, especially those involving organic compounds.
• Water (\(\mathrm{H}_2\mathrm{O}\)): A universal solvent, an essential product of many reactions.

So, comprehending reaction products empowers one in anticipating the direction of chemical reactions and their applications.

Phosgene Formation

Phosgene, represented as \(\mathrm{COCl}_2\), is a significant product formed when carbon monoxide \(\mathrm{CO}\) reacts with chlorine \(\mathrm{Cl}_2\). Phosgene is a less common chemical in natural settings but extremely pivotal in certain industrial applications.
This substance is notable due to

• Formation: Occurs when \(\mathrm{CO}\) combines with \(\mathrm{Cl}_2\) under controlled conditions.
• Uses: Vital in producing plastics and resins.
• Safety: Its presence requires careful handling due to potential toxicity.

Understanding phosgene's formation helps not only in industrial contexts but also offers insights into chemical synthesis and reaction pathways that transform everyday chemicals into crucial industrial substances.