All questions of Carbon and Its Compounds for Class 8 Exam

Understanding Brown Coal
Brown coal is commonly referred to as lignite, which is a type of coal that is characterized by its lower carbon content and distinct properties.
Characteristics of Lignite (Brown Coal)
- Carbon Content: Lignite has a carbon content of about 25-35%, which is significantly lower than that of higher-ranked coals like bituminous and anthracite.
- Moisture Content: Lignite contains a high moisture content, often between 30-60%. This moisture affects its energy density and makes it less efficient compared to harder coals.
- Color and Texture: Lignite is usually brownish in color and has a soft, crumbly texture, making it easily breakable.
Formation and Uses
- Formation: Lignite is formed from peat, the precursor to coal, through geological processes that involve heat and pressure over millions of years. It is the earliest stage in the coal formation process.
- Uses: Due to its lower energy output, lignite is primarily used for electricity generation in power plants and is often found close to surface deposits, making it easier and cheaper to mine.
Comparison with Other Coal Types
- Bituminous Coal: Contains more carbon (45-86%) and is used for electricity generation and steel production.
- Anthracite: Contains the highest carbon content (86-97%) and is known for its high energy output and burning efficiency.
In summary, lignite or brown coal is distinguished by its lower carbon content, higher moisture, and unique formation. It serves important functions, especially in energy production, despite its limitations compared to higher-ranked coals.

Understanding Carbon Dioxide
Carbon dioxide (CO2) is an essential gas in our atmosphere, and several key facts clarify its characteristics.
Colorless and Odorless
- CO2 is indeed a colorless and odorless gas, which means it cannot be seen or smelled in its natural state.
- This property makes it less noticeable in the environment, unlike other gases that might have distinct odors.
Non-flammable Nature
- One of the most important properties of carbon dioxide is that it does not support combustion.
- This means that fire cannot burn in the presence of CO2, making it a useful gas in fire extinguishers.
State at Room Temperature
- Contrary to option b, carbon dioxide is not a solid at room temperature.
- It exists as a gas under standard atmospheric conditions. However, it can be found in solid form as dry ice, but only at very low temperatures.
Toxicity and Suffocation
- While CO2 is not classified as a toxic gas in the same way that carbon monoxide is, high concentrations can lead to suffocation.
- This occurs because CO2 displaces oxygen in the air, leading to insufficient oxygen for breathing.
Density Compared to Air
- Option d is also incorrect as carbon dioxide is denser than air, causing it to settle rather than rise in the atmosphere.
In conclusion, the correct answer is option 'A': Carbon dioxide is a colorless, odorless gas that does not support combustion, making it a unique and important component of our atmosphere.

Understanding Destructive Distillation
Destructive distillation is the process where carbon compounds are broken down by heat in the absence of air. This method primarily focuses on the thermal decomposition of organic materials.
Key Features of Destructive Distillation:
- Absence of Air:
The process takes place without oxygen, preventing combustion. This allows the materials to break down without burning.
- Heating Organic Materials:
Carbon-based substances, like wood, coal, or organic waste, are subjected to high temperatures. This heat causes the materials to decompose into simpler compounds.
- Production of Byproducts:
Destructive distillation produces various useful byproducts, including:
- Coal Gas: A mixture of gases that can be used as a fuel.
- Tar: A thick, black liquid that can be further refined into chemicals or used for paving.
- Ammoniacal Liquor: A solution containing ammonia, which can be used in fertilizers.
Applications of Destructive Distillation:
- Fuel Production:
The gas produced can be used for heating or as an energy source in industries.
- Chemical Manufacturing:
Byproducts like tar are essential in making dyes, drugs, and plastics.
- Charcoal Creation:
The carbon-rich residue left after distillation is charcoal, which has applications in cooking and filtration.
Conclusion
In summary, destructive distillation is a vital process in chemistry that allows for the conversion of carbon compounds into useful products without the influence of air, making it significant for both industrial applications and environmental sustainability.

Reaction of Carbon with Limited Oxygen
When carbon reacts with a limited amount of oxygen, the primary product formed is carbon monoxide (CO). Here's a detailed explanation of this reaction:
Understanding Combustion
- Combustion is a chemical process where a substance reacts with oxygen to produce energy, light, and new compounds.
Limited Oxygen Conditions
- When carbon burns in a limited supply of oxygen, complete combustion does not occur.
- Instead of forming carbon dioxide (CO2), which requires a sufficient amount of oxygen, the reaction results in the formation of carbon monoxide (CO).
Formation of Carbon Monoxide
- The chemical reaction can be summarized as follows:
- C + ½ O2 → CO
- In this reaction, one carbon atom reacts with half a molecule of oxygen to form one molecule of carbon monoxide.
Characteristics of Carbon Monoxide
- Toxicity: Carbon monoxide is a colorless, odorless gas that is highly toxic to humans and animals.
- Incomplete Combustion: It is a product of incomplete combustion, commonly seen in situations like car exhaust or poorly ventilated heating systems.
Conclusion
- Therefore, when carbon reacts with a limited amount of oxygen, the correct answer is option 'B' - Carbon Monoxide.
- This emphasizes the importance of ensuring sufficient oxygen supply during combustion processes to avoid hazardous situations.