Question

Incomplete combustion of petrol or diesel in automobile engines can be best detected by testing the fuel gases for the presence of (a) sulphur dioxide (b) nitrogen dioxide (c) carbon monoxide (d) carbon monoxide and water vapour

Short answer

(c) carbon monoxide

Step-by-step solution

Understanding Incomplete Combustion

Incomplete combustion of petrol or diesel occurs when there isn't enough oxygen to allow the fuel to react completely to form carbon dioxide (CO₂) and water (H₂O). Instead, this can result in the production of other gases such as carbon monoxide (CO) due to incomplete oxidation.

Identifying Produced Compounds

In incomplete combustion, carbon monoxide (CO) is a major byproduct due to insufficient oxygen for the conversion of carbon to carbon dioxide. Water vapor (H₂O) is another probable byproduct, as it is commonly produced in combustion reactions.

Analyzing Multiple-Choice Options

Go through the options provided: - (a) Sulphur dioxide: Typically produced from the combustion of fuel containing sulfur, not directly from incomplete combustion. - (b) Nitrogen dioxide: Formed from nitrogen in the air at high temperatures, not typically a primary indicator of incomplete combustion. - (c) Carbon monoxide: A direct result of incomplete combustion. - (d) Carbon monoxide and water vapor: Incomplete combustion can result in both these products. However, water vapor's presence is not unique to incomplete combustion.

Conclusion: Best Indicator of Incomplete Combustion

The presence of carbon monoxide (Option c) is the best indicator of incomplete combustion, as it directly arises from the lack of sufficient oxygen during the combustion process.

Key concepts

Carbon Monoxide Detection

Carbon monoxide (CO) is a colorless and odorless gas that is produced during incomplete combustion. Due to its dangerous nature, detecting carbon monoxide is crucial in several settings, particularly in automobile emissions and domestic environments.

Here are some methods commonly used for carbon monoxide detection:

• **Chemical Indicator Paper**: These papers change color in the presence of carbon monoxide. They are simple to use but might not be very precise.
• **CO Detectors**: These are electronic devices that sound an alarm when carbon monoxide is detected. They are often installed in homes to alert residents of potentially dangerous CO levels.
• **Infrared Gas Analyzers**: These devices use infrared sensors to detect the presence of carbon monoxide. They are highly accurate and are often used in scientific and industrial applications.

Understanding carbon monoxide's properties and the ways to detect it can help in maintaining safer environments, particularly where fuel combustion occurs.

Combustion Reactions

Combustion reactions involve the burning of a fuel in the presence of oxygen to produce heat and light. This chemical process is fundamental in engines, industrial processes, and even household applications like cooking and heating.

In general, a combustion reaction can be represented as:\[ \text{Fuel} + \text{Oxygen} \rightarrow \text{Combustion Products (like } \text{CO}_2\text{, H}_2\text{O)} \]It's important to distinguish between complete and incomplete combustion:

• **Complete Combustion**: Occurs when sufficient oxygen is available, resulting in the formation of carbon dioxide (CO₂) and water vapor (H₂O). This type of combustion releases the maximum amount of energy stored in the fuel.
• **Incomplete Combustion**: Occurs when there's not enough oxygen, leading to the formation of byproducts like carbon monoxide (CO) and sometimes soot. This is less efficient and often releases harmful gases.

Complete understanding of these reactions is vital, particularly for developing efficient and cleaner burning engines.

Oxidation Process in Engines

The oxidation process in engines is part of the broader combustion reaction that powers vehicles. When the fuel inside an engine combusts, it undergoes oxidation, which is an exothermic reaction, releasing energy and heat.

Here's how the process unfolds:

• **Initiation**: When the fuel-air mixture is ignited within the engine cylinder, the chemical bonds in the fuel break, releasing energy.
• **Propagation**: The energy released causes a chain reaction where fuel molecules continue to oxidize, producing gases like CO₂ and water vapor under ideal conditions.
• **Termination**: The reaction continues until the fuel is consumed or the oxygen supply is depleted.

Issues arise with incomplete oxidation due to insufficient oxygen, leading to the production of carbon monoxide (CO). This not only reduces fuel efficiency but also increases emissions of harmful pollutants. Therefore, understanding and optimizing the oxidation process is crucial for developing more efficient and environmentally friendly engines.