Test: Carbon and Its Compounds - Class 8 MCQ

Diamond is recognized as the hardest natural substance due to its crystalline structure, where each carbon atom is tetrahedrally bonded to four other carbon atoms. This rigid arrangement makes diamond incredibly durable and resistant to scratching.

In the baking industry, carbon dioxide is used to make dough rise. When baking soda reacts with acidic components like vinegar, it produces CO2, which forms bubbles and causes the dough to expand, creating light and airy baked goods.

The process of breaking down carbon compounds through heating in the absence of air is known as destructive distillation. This method is used to produce various forms of carbon, including charcoal and coke.

Charcoal's porous structure allows it to trap gases, liquids, and solids on its surface, making it an effective absorbent. This property is utilized in various applications, including air and water purification.

When carbon burns in sufficient oxygen, it produces carbon dioxide (CO2). This gas is a significant contributor to the greenhouse effect and is vital for photosynthesis in plants.

Carbon dioxide is indeed a colorless, odorless gas that does not support combustion. This property makes it useful in fire extinguishers to smother flames, as it displaces oxygen.

Activated charcoal is widely used in water purification due to its high surface area and porous structure, which allows it to adsorb impurities and contaminants effectively, making water safe to drink.

Coke is primarily used as a reducing agent in the extraction of metals from their ores. Its high carbon content allows it to react with metal oxides, removing oxygen and yielding pure metals.

Lignite, commonly referred to as brown coal, is the lowest grade of coal, containing about 60-70% carbon. It is used primarily for electricity generation but has a higher moisture content and lower energy value compared to higher-grade coals.

Graphite is primarily used in pencils because it is soft and can leave a mark on paper. Its layered structure allows the sheets to slide over each other easily, which is ideal for writing.

A covalent bond is formed when atoms share electrons. Carbon's ability to form four covalent bonds enables it to create complex organic molecules, which are essential for life.

Anthracite is the highest grade of coal, containing over 90% carbon. It burns efficiently and produces minimal smoke, making it a preferred choice for heating and industrial processes.

Carbonization is the slow process through which ancient plant matter transforms into coal over millions of years. This process involves heat and pressure that gradually convert organic material into carbon-rich coal.

The chemical formula for carbon monoxide is CO, indicating that it consists of one carbon atom and one oxygen atom. It is a colorless, odorless gas that is highly toxic and produced by incomplete combustion of carbon-containing fuels.

When carbon reacts with a limited amount of oxygen, it forms carbon monoxide (CO). This gas is particularly dangerous because it can prevent oxygen from binding with hemoglobin in the blood, leading to asphyxiation.

Diamond possesses a very high melting point, around 3500°C, due to the strong covalent bonds between carbon atoms in its structure. This makes it suitable for high-temperature applications.

The increase in carbon dioxide levels in the atmosphere is a significant contributor to global warming. CO2 is a greenhouse gas that traps heat, leading to changes in climate patterns and environmental conditions.

Buckminsterfullerene, commonly referred to as C60, is a unique allotrope of carbon with a spherical structure. Discovered in 1985, it has potential applications in materials science and nanotechnology.

Carbon's ability to form a large variety of compounds is largely attributed to its valency of 4, which allows it to form stable covalent bonds with many other elements, including itself. This unique property enables carbon to create long chains and complex structures, leading to millions of known compounds.

When carbon dioxide is passed through lime water, it reacts with calcium hydroxide to form calcium carbonate, which is insoluble in water and causes the lime water to turn milky. This reaction is often used as a test for the presence of CO2.