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.