a. A carbon atom forms a ….……………. bond with other atoms. In this bond the two atoms …. electrons.

Answer: A carbon atom forms a covalent bond with other atoms. In this bond the two atoms share. electrons.

b. All the carbon bonds in a saturated hydrocarbon ….……………. electrons.

Answer: All the carbon bonds in a saturated hydrocarbon Share electrons.

c. At least one carbon bond in an unsaturated hydrocarbon is ….…………….

Answer: At least one carbon bond in an unsaturated hydrocarbon is Multiple

d. ….……………. is the essential element in all the organic compounds.

Answer: Carbon is the essential element in all the organic compounds.

e. The element hydrogen is present in ….. organic compound.

Answer: The element hydrogen is present in all organic compound.

2. Answer the following questions

a. Why are carbon and its compounds used as fuels?

(1) The term “carbon” originates from the Latin word “carbo,” which translates to coal. Carbon constitutes approximately 0.27% of the Earth’s crust, existing in various forms such as carbonates, coal, and petroleum. Among these, coal stands out as a non-crystalline and amorphous manifestation of carbon. It holds the status of being a fossil fuel, integral to many aspects of human activity and industry.

(2) Peat, lignite, bituminous, and anthracite represent the four classifications of coal, ordered by their ascending carbon content and the heat they generate. Meanwhile, charcoal and coke serve as alternative amorphous carbon forms employed as fuel sources.

(3) Carbon compounds, like hydrocarbons, are composed of carbon and hydrogen, rendering them highly combustible. For instance, methane (CH4) found in natural gas is notably flammable. When ignited, it reacts with oxygen, producing a distinctive bluish flame. This combustion reaction releases approximately 213 Kcal/mol of heat. Notably, methane undergoes complete combustion in this process.

Chemical reaction:

CH4 + 2O2 → CO2 + 2H2O + Heat

b. In which compound forms does carbon occur?

Answer: Carbon takes on different forms in its combined state, including:

1. Carbon dioxide and carbonates like calcium carbonate, are present in materials such as marble and calamine (ZnCO3).
2. Fossil fuels such as coal, petroleum, and natural gas.
3. Carbon-containing nutrients are found in carbohydrates, proteins, and fats.
4. Natural fibres like cotton, wool, and silk.
5. Hydrocarbons, compounds composed of carbon and hydrogen.

1. Write the uses of the diamond.

Answer. Diamonds serve various purposes, including:

• Utilization in glass cutting and rock drilling machinery due to their exceptional hardness.
• Adorning jewellery and decorative items, adding a touch of elegance and luxury.
• Application in eye surgery through diamond knives, ensuring precision and accuracy.
• Employing diamond dust for polishing purposes, particularly in refining other diamonds.
• Crafting windows for shielding against radiation in space and outfitting artificial satellites with resilient components.

3. Explain the difference:

a. Diamond and graphite.

Graphite: Graphite is soft, opaque, and black in color. It has a slippery feel due to its layered structure. Graphite is a good conductor of electricity and heat due to the presence of delocalized electrons within its layers.

Diamond: Diamond is the hardest known natural material, renowned for its exceptional hardness and brilliance. It is transparent and colorless (although impurities can give it various colors). Diamond is a poor conductor of electricity due to its tightly bound electrons and lack of free electrons.

Uses:

Graphite: Graphite is widely used as a lubricant, in pencils, and as a moderator in nuclear reactors. It is also used in various industries, including metallurgy and electronics.

Diamond: Diamonds are primarily used in jewelry due to their beauty and durability. They are also utilized in cutting tools, such as diamond-tipped drills and saws, due to their hardness. Additionally, diamonds have applications in various industrial processes, including machining, grinding, and polishing.

b. Crystalline and non-crystalline forms of carbon.

Answer: Crystalline and non-crystalline forms of carbon

The main differences between crystalline and non-crystalline forms of carbon lie in their molecular structure, properties, and behaviour:

Molecular Structure:

Crystalline Carbon: Crystalline forms of carbon, such as diamond and graphite, have well-defined, ordered atomic arrangements. In diamond, carbon atoms are arranged in a three-dimensional, tetrahedral lattice structure, while graphite consists of layers of carbon atoms arranged in a hexagonal lattice.

Non-Crystalline Carbon: Non-crystalline forms, like amorphous carbon, lack long-range order in their atomic arrangement. Instead, they have a disordered, random structure with irregular bonding between atoms.

Properties:

Crystalline Carbon: Crystalline carbon materials exhibit unique properties based on their molecular structure. For example, diamond is the hardest naturally occurring substance, transparent, and has excellent thermal conductivity, while graphite is soft, opaque, and a good conductor of electricity.

Non-Crystalline Carbon: Non-crystalline carbon materials tend to have properties that are more uniform and isotropic due to their random atomic arrangement. They may exhibit characteristics such as low density, high porosity, and amorphous appearance.

Behavior:

Crystalline Carbon: Crystalline carbon materials often display anisotropic properties, meaning their properties vary depending on the direction of measurement relative to the crystal structure. They may also have specific cleavage planes along which they tend to fracture.

Non-Crystalline Carbon: Non-crystalline carbon materials typically exhibit isotropic properties, meaning their properties are the same in all directions. They may be more resistant to fracture along specific planes and have a more uniform response to external stimuli.

4. Write scientific reasons

a. Graphite is a conductor of electricity.

Answer: In graphite, carbon atoms are interconnected in a manner where each carbon atom forms bonds with three neighbouring carbon atoms, shaping a hexagonal layered structure. This configuration allows for the presence of free electrons within the layers of graphite. These liberated electrons exhibit mobility throughout the entire layer, contributing to graphite’s conductivity. Consequently, graphite demonstrates proficiency in conducting electricity due to the availability and movement of these free electrons.

b. Graphite is not used in ornaments.

Answer: Graphite presents as a black, soft, brittle, and lacklustre manifestation of carbon, lacking both malleability and ductility. These distinctive properties render graphite unsuitable for ornamentation purposes. Consequently, graphite finds no application in the crafting of ornaments.

C. Limewater turns milky when CO2 is passed through it.

Answer. Traditionally, limewater denotes a dilute solution containing the alkaline compound calcium hydroxide (Ca(OH)2). When carbon dioxide (CO2) is introduced into limewater, it undergoes a reaction with calcium hydroxide, resulting in the formation of insoluble particles known as precipitates, primarily composed of calcium carbonate (CaCO3). Calcium carbonate, classified as a weak basic salt, manifests as a milky white precipitate in the solution. Consequently, the once clear limewater transforms into a milky appearance upon the passage of CO2 gas.

d. Biogas is an eco-friendly fuel.

Answer: Biogas, generated through the decomposition of organic materials like animal dung, dry leaves, and wet garbage in specialized biogas plants, primarily consists of methane gas. Methane, also known as biogas, serves as an economical and environmentally friendly fuel source, particularly for cooking purposes. Composed of approximately 55% to 60% methane and the remaining portion being carbon dioxide, biogas combustion minimizes the release of harmful pollutants into the atmosphere. Not only is biogas easy to use as a fuel, but the process also yields valuable organic fertilizer as a byproduct, enhancing its eco-friendly credentials. Overall, biogas has emerged as a sustainable and eco-friendly fuel option for various energy needs.

5. Explain the following.

a. Diamond, graphite, and fullerenes are crystalline forms of carbon.

Answer:

• Carbon exhibits the phenomenon of allotropy, wherein it can exist in multiple forms in nature.
• Despite sharing similar chemical properties, these various forms of carbon display distinct physical characteristics.
• Carbon occurs in both crystalline and non-crystalline (amorphous) states.

• Crystalline carbon allotropes possess a regular and well-defined atomic arrangement, resulting in high melting and boiling points.
• They also feature specific geometric shapes, sharp edges, and plane surfaces. Notable examples of crystalline carbon include diamond, graphite, and fullerene.

• Diamond boasts a tetragonal three-dimensional structure, with each carbon atom forming four covalent bonds with neighboring atoms, rendering it exceptionally hard. Renowned as the hardest natural substance, pure diamond exhibits brilliance and durability.

• In contrast, graphite’s structure comprises layers of carbon atoms arranged in a hexagonal lattice, with each carbon atom bonded to three others. These layers can easily slide over each other, giving graphite its characteristic slippery texture. Individual layers of graphite are known as graphene.

• Fullerene, a less common allotrope, is found in soot and interstellar space.
• The archetype of fullerene, Buckminsterfullerene (C60), derives its name from architect Richard Buckminster Fuller, as its structure resembles his geodesic dome design.
• Fullerene molecules exist in various forms, such as buckyballs and buckytubes, containing 30 to 900 carbon atoms per molecule.
• Additional examples include C70, C76, C82, and C86, which occur in small quantities in soot.

b. Methane is called marsh gas.

Answer: Methane originates from the breakdown of organic materials in wetland environments like swamps and marshes. When methane rises to the surface in these areas, it’s commonly referred to as marsh gas.

c. Petrol, diesel, coal are fossil fuels.

Answer: (i) Fossil fuels, derived from natural processes like anaerobic decomposition, are rich in carbon. The term “carbon” originates from the Latin word ‘Carbo’, signifying coal.

(ii) Coal forms from ancient vegetation trapped in swamps, evolving over millions of years under heat and pressure into dense layers known as peat. Subsequent burial further transforms peat into coal.

(iii) Petrol and diesel stem from mineral oil, also known as crude oil or petroleum, originating from ancient marine plant and animal remains. Over millions of years, these organic materials undergo significant geological processes, resulting in the formation of mineral oil.

(iv) Mineral oil, often found in seabed rocks, yields petrol and diesel through fractional distillation. “Petroleum” stems from the Latin term ‘Rock oil’. Thus, petrol, diesel, and coal are classified as fossil fuels.

e. Use of CO2 in fire extinguisher.

Answer. CO2 fire extinguishers, being non-corrosive and non-conductive, are ideal for addressing small-scale fires involving electrical and electronic equipment. However, their efficacy may be limited against larger fires.

f. Practical uses of CO2.

CO2 finds practical applications in various domains:

1. CO2 plays a crucial role in carbonating beverages.
2. Utilized in fire extinguishers, CO2, obtained through chemical reactions or stored under pressure, proves effective in managing emergencies.
3. Liquid CO2 serves as a solvent in contemporary and environmentally friendly dry cleaning processes.
4. Solid carbon dioxide, commonly known as dry ice, serves in cold storage, ensuring the preservation and transport of perishable goods like milk and frozen substances.
5. Additionally, it contributes to creating special mist effects in theatrical productions and films

• Write two physical properties each.

a. Diamond

Answer: The properties of diamond are:

1. Diamond is renowned as the hardest natural material. boasts a density of 3.5 g/cm3 and a melting point of 3500°C.
2. Heating the diamond to 800°C in oxygen yields only CO2 without any other byproduct.
3. It remains insoluble in solvents and unaffected by acids or bases.
4. Moreover, its lack of free electrons renders the diamond a poor conductor of electricity.

b. Charcoal

• Charcoal derived from animals is crafted from their bones, horns, and similar materials.
• plant-derived from charcoal results from the incomplete combustion of wood, typically in conditions of limited air supply.

c. Fullerenes

Fullerenes characteristics:

• Fullerene molecules manifest in structures like buckyballs and buckytubes.
• A single fullerene molecule may contain anywhere from 30 to 900 carbon atoms.
• Solubility in organic solvents like carbon disulphide and chlorobenzene is a notable property of fullerenes.

7. Complete the following Chemical reactions.

1. ………………..+………………..→ CO + 2H2O + Heat

2. ………………..+………………..→ HCl + Cl + HCl

3. 2 NaOH + CO2 →………………..+………………..

Answer.

• CH_{4   + 2}O₂ → CO2 + 2H₂O + Heat
• CH_{4     +} Cl₂ → CH₃Cl + HCl
• 2 NaOH + CO₂ →Na₂CO3 +H2O

8. Write answers to the following in detail.

a. What are the different types of coal? What are their uses?

• Coal, a fossil fuel, encompasses carbon, hydrogen, oxygen, as well as nitrogen, phosphorus, and sulphur. It’s solid and categorized into four types:
• Peat: The initial stage of coal formation, it has high water content and less than 60% carbon, resulting in limited heat production.
• Lignite: Evolved from peat due to elevated pressure and temperature, it consists of 60 to 70% carbon, marking the second stage.
• Bituminous Coal: The third stage, comprising 70 to 90% carbon.
• Anthracite: Renowned as the purest coal form, it’s hard and contains approximately 95% carbon.

Coal Used for various purposes:

• As a fuel, coal powers factories and homes alike.
• It’s crucial in the production of coke, coal gas, and coal tar.
• Coal plays a pivotal role in thermal power plants, facilitating electricity generation.

b. How will you prove experimentally that graphite is good conductor of electricity?

Answer:

Materials needed: Pencil lead, electrical wires, battery or cell, small bulb, etc.

Procedure:

Step 1: Extract the lead from a pencil and set up the apparatus as illustrated in the diagram.

Step 2: Activate the electric current in the circuit. Upon passing the electric current through the circuit, the bulb illuminates.

Explanation:

This experiment demonstrates the conductivity of graphite. Graphite, being a good conductor of electricity, contains free electrons that continuously move within its layers. These free electrons enable the conduction of electricity through the pencil lead.

c. Explain the properties of carbon.

Answer: Answer: Allotropic nature of Carbon: Some elements occur in nature in more than one form. The chemical properties of these different forms are the same but their physical properties are different. This property of elements is called allotropy. Carbon shows the property of allotropy.

Carbon exhibits allotropy, a phenomenon where an element can exist in multiple forms with identical chemical properties but distinct physical attributes. Carbon demonstrates this characteristic through its various allotropes.

(A) Crystalline Forms:

Diamond, graphite, and fullerene are the three crystalline allotropes of carbon.

These forms showcase a precise and orderly arrangement of carbon atoms.

Comprising solely of carbon atoms, they boast high melting and boiling points.

Crystalline forms exhibit distinct geometrical shapes with sharp edges and flat surfaces.

(B) Amorphous Forms or Non-crystalline Forms:

Coal, charcoal, and coke represent non-crystalline forms of carbon.

In these forms, carbon atoms lack a regular arrangement.

Besides carbon atoms, they contain elements like hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

Non-crystalline forms generally possess lower melting and boiling points compared to crystalline forms. These forms are primarily utilized as fuels.

d. Classify carbon.

9. How will you verify the properties of carbon dioxide?

Answer: The properties of carbon dioxide can be demonstrated through several experiments:

• When a lit candle is introduced into a gas jar filled with carbon dioxide, it immediately extinguishes. This reveals that carbon dioxide does not support combustion and is a non-combustible gas.
• Passing carbon dioxide gas through lime water results in the solution turning milky. This occurs due to the formation of insoluble calcium carbonate.
• When moist blue litmus paper is exposed to carbon dioxide in a gas jar, it undergoes a color change to red, indicating the acidic nature of carbon dioxide.
• Carbon dioxide exhibits fair solubility in water, leading to the formation of carbonic acid upon dissolution.