Carbon Important Questions

---

Very Short Answer Questions (1 Marks Questions)

Ques 1: Which functional group is represented by —CHO?

Ans. Aldehydes is represented by —CHO.

Ques 2. What is the name of the homologous series of compounds C₃H₈?

Ans. Alkanes is the name of the homologous series of C₃H₈.

Ques 3. What is the count of pentane isomers?

Ans. 3 is the count of pentane isomers.

Ques 4. Which substances will undergo additional reactions?

Ans. C₂H₄ will undergo addition reaction.

Ques 5.What arе thе most prеvalеnt carbon allotropes?

Ans. Diamond, graphitе, and fullerene arе еxamplеs of common carbon allotropes.

Ques 6. What is carbon's atomic mass?

Ans. Carbon has an atomic mass of roughly 12. 01 atomic mass units.

Ques 7. What еxactly is carbon fixation?

Ans. Carbon fixation is thе procеss of converting atmosphеric carbon dioxidе into organic molеculеs via photosynthesis or chеmosynthеsis. 

Ques 8. What gas is released when ethanoic acid reacts with NaHCO₃?

Ans. The gas which is released is CO₂.

---

Short Answer Questions (2 Marks Questions)

Ques 1. In welding, a mixture of oxygen and ethyne is used instead of a mixture of ethyne and air. Can you explain why?

Ans. The reason for using a mixture of oxygen and ethyne for welding is to ensure complete combustion. 

• When ethyne is burned in the air, the combustion is incomplete, resulting in a sooty flame due to insufficient oxygen. 
• In contrast, burning ethyne in the presence of pure oxygen produces a clean and high-temperature flame (reaching up to 3000°C) due to complete combustion. 
• This oxy-acetylene flame is ideal for welding as it provides the necessary heat.
• While air cannot reach the same high temperature required for efficient welding.

Ques 2. What makes carbon highly significant?

Ans. Carbon holds great significance due to its essential role in all known biological systems, without which life would not exist. 

• It is not only present in food and wood but also forms the basis of hydrocarbons like fossil fuels, methane gas, and crude oil. 
• Carbon fibers, known for their strength, lightweight nature, and durability, find diverse applications. 
• They are utilized in the manufacturing of various items, including tennis rackets, fishing poles, airplanes, rockets, and even industrial diamonds used for drilling and cutting rocks.

Ques 3. What experimental methods can be employed to differentiate between an alcohol and a carboxylic acid?

Ans. Experimental differentiation between an alcohol and a carboxylic acid can be achieved by examining their functional groups. Alcohols contain the OH group, while carboxylic acids possess the COOH group. To distinguish between the two, various tests can be conducted.

Ques 4. What are the two properties of carbon that contribute to the vast number of carbon compounds observed in our surroundings?

Ans. The two properties of carbon that account for the extensive array of carbon compounds are its ability to form covalent bonds and its tetravalency.

1. Covalent Bonding: Carbon has the unique ability to form strong covalent bonds with other carbon atoms and various other elements. 

• This bonding allows carbon atoms to share electrons, resulting in the formation of stable molecules. 
• Covalent bonds enable carbon to create diverse and complex structures, giving rise to a wide range of compounds with different properties.

2. Tetravalency: Carbon has four valence electrons in its outermost shell, allowing it to form up to four covalent bonds. 

• This tetravalent nature of carbon provides immense flexibility in bonding with other atoms, including carbon itself. 
• It enables the formation of long carbon chains, branched structures, and rings, leading to the vast structural diversity observed in carbon compounds.
• Due to these properties, carbon can form countless organic compounds, such as hydrocarbons, alcohols, carboxylic acids, polymers, and more. 
• The combination of covalent bonding and tetravalency in carbon contributes to the richness and complexity of carbon chemistry.
• It makes it the foundation of life and the basis for the diverse array of carbon compounds we encounter in our daily lives.

Ques 5. What is the reason behind the low melting and boiling points of covalent compounds? (2020)

Ans. Covalent compounds have low melting and boiling points due to the weak intermolecular forces between their molecules. 

• In covalent compounds, bonding occurs through the sharing of electrons between atoms. 
• The intermolecular forces, such as London dispersion forces, dipole-dipole interactions, or hydrogen bonding, are relatively weak compared to the strong covalent bonds within the molecules.
•  As a result, only a small amount of heat energy is required to overcome these weak forces 
• It converts the covalent compounds from solid to liquid or gas phase, leading to their low melting and boiling points.

Ques 6. What are covalent compounds and how do they differ from ionic compounds? Also, list three characteristic properties of covalent compounds. (Delhi 2016)

Ans. Covalent compounds are compounds formed through the sharing of valence electrons between atoms. For example, a hydrogen molecule is formed when two hydrogen atoms share their electrons.

• They differ from ionic compounds, which are formed through the complete transfer of electrons from one atom to another. 
• For instance, NaCl is formed when a sodium atom completely transfers one valence electron to the outer shell of a chlorine atom.

The characteristic properties of covalent compounds include:

1. Solubility: Covalent compounds are generally insoluble or have low solubility in water, but they are soluble in organic solvents. This is because covalent compounds do not dissociate into ions in water like ionic compounds do.
2. Melting and boiling points: Covalent compounds have lower melting and boiling points compared to ionic compounds. This is because the intermolecular forces between covalent molecules, such as van der Waals forces, are weaker than the electrostatic forces between ions in ionic compounds.
3. Electrical conductivity: Covalent compounds do not conduct electricity in their pure form. This is because they do not contain freely moving ions or delocalized electrons that can carry an electric current. However, some covalent compounds can conduct electricity when they are ionized or undergo chemical reactions.

Also Read:

---

Long Answer Questions (3 Marks Questions)

Ques 1. What is a homologous series? Explain with an example.

Ans. A homologous series is a group of organic compounds that share the same functional group and have a similar chemical structure, with a difference of -CH₂ group between each member.

Characteristics of a homologous series:

(i) They have the same general formula, which can be used to represent all members of the series. 

For example, the general formula for the alkane homologous series is CⁿH²ⁿ⁺².

(ii) Each successive member differs by a -CH₂ group.

(iii) The molecular mass of adjacent homologues differs by 14u.

(iv) Chemical properties of the compounds in a homologous series are similar.

(v) As the molecular mass increases, there is a gradual change in the physical properties of the compounds.

Example: The alkane homologous series includes methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀), where the difference between each member is a -CH₂ unit.

Ques 2. What are the distinguishing physical and chemical properties of ethanol and ethanoic acid?

Ans. Ethanol and ethanoic acid can be differentiated based on their physical and chemical properties:

Physical Properties:

1. Odor: Ethanol has a characteristic alcoholic smell, while ethanoic acid has a pungent vinegar-like odor.
2. State: Ethanol is a colorless liquid at room temperature, while ethanoic acid is also a liquid but may exhibit a slightly different appearance.
3. Solubility: Ethanol is soluble in water, whereas ethanoic acid is highly soluble in water.

Chemical Properties:

1. Reactivity with Bases: Ethanol does not react with bases, whereas ethanoic acid reacts with bases to form salts known as acetates.
2. Reaction with Carbonates: Ethanol does not react with carbonates, while ethanoic acid reacts with carbonates to produce carbon dioxide gas.
3. Reaction with Metals: Ethanol does not react with metals, whereas ethanoic acid can react with certain metals to produce hydrogen gas.

By observing these differences in physical and chemical properties, ethanol and ethanoic acid can be distinguished from each other.

Ques 3. What is hydrogenation? What is its industrial application?

Ans. Hydrogenation is a chemical reaction where hydrogen gas is added to another molecule in the presence of a catalyst.

• An example of hydrogenation is the addition of hydrogen to an alkene, converting it into an alkane.
•  For instance, ethene (CH₂=CH₂) can be hydrogenated to form ethane (CH₃CH₃).

The industrial application of hydrogenation is widespread. Some of its uses include:

1. Production of Saturated Fats: Hydrogenation is employed in the food industry to convert unsaturated fats into saturated fats, resulting in the production of solid fats like vegetable ghee from vegetable oils.
2. Manufacturing of Petrochemicals: Hydrogenation plays a vital role in the production of various petrochemicals, such as the conversion of unsaturated hydrocarbons into more stable and usable saturated hydrocarbons.
3. Hydrogenation of Oils: Hydrogenation is utilized in the production of hydrogenated oils, which have enhanced stability and longer shelf life. These oils are used in food processing and the manufacture of margarine, spreads, and other edible products.
4. Pharmaceutical Industry: Hydrogenation is employed in the synthesis of pharmaceutical compounds, including the reduction of functional groups and the production of intermediates for drug manufacturing.

In summary, hydrogenation is a versatile process with various industrial applications, ranging from food production to petrochemicals and pharmaceuticals.

Ques 4. What is the reason behind the extensive use of carbon and its compounds as fuels in various applications?

Ans. Carbon and its compounds are widely used as fuels in numerous applications due to the following reasons:

1. High Energy Content: Carbon-based fuels possess a high energy content, which is released during combustion. 

• This energy is harnessed for various purposes, including heating, power generation, and transportation. 
• Carbon compounds, such as hydrocarbons, store a significant amount of energy in their chemical bonds, making them efficient sources of fuel.

2. Availability: Carbon is abundantly available on Earth, and carbon-based compounds can be found in various forms, such as fossil fuels (coal, oil, and natural gas), biomass, and organic matter. 

• This widespread availability makes carbon fuels easily accessible and economically viable for energy production.

3. Combustion Properties: Carbon fuels exhibit favorable combustion properties, including high ignition temperatures and controlled burning rates. 

• They release heat energy in a controlled manner, allowing for safe and efficient utilization in different applications. 
• Carbon compounds also produce carbon dioxide (CO₂) and water (H₂O) as byproducts during combustion
• Which are relatively less harmful to the environment compared to other combustion products.

Ques 5. How does scum form when hard water is treated with soap?

Ans. When hard water is treated with soap, scum is formed due to a reaction between soap molecules and the ions present in hard water, particularly calcium and magnesium ions. 

• Hard water contains dissolved calcium and magnesium salts, primarily calcium carbonate (CaCO₃) and magnesium carbonate (MgCO₃).
• When soap is added to hard water, the sodium or potassium salts of fatty acids present in the soap undergo a chemical reaction known as saponification. 
• During saponification, the soap molecules react with the calcium and magnesium ions in the hard water to form insoluble compounds called calcium or magnesium soaps.
•  These soaps appear as a white, sticky residue known as scum.

The formation of scum occurs because the calcium and magnesium ions in hard water react with the soap molecules, causing them to precipitate out of the solution. This process reduces the effectiveness of soap for cleaning purposes, as the scum does not readily dissolve in water and can leave a residue on surfaces, fabrics, and skin.

---

Very Long Answer Questions (5 Marks Questions)

Ques 1. Why is it not possible for carbon to attain a noble gas electronic configuration by gaining or losing electrons to form compounds? What are the types of bonds formed in ionic compounds and carbon compounds? Additionally, explain the reason for carbon compounds being poor conductors of electricity. (Foreign 2015, AI 2014)

Ans. Ionic compounds are formed by the transfer of electrons from one element to another, resulting in the formation of electrovalent bonds. However, carbon, with four electrons in its outermost shell, cannot attain a noble gas electronic configuration by either gaining or losing electrons. This is because:

1. Gaining four electrons: If carbon were to gain four electrons to attain a noble gas configuration, it would result in a highly unstable arrangement. 

• The increased number of electrons would create strong repulsive forces within the atom, making it energetically unfavorable.

2. Losing four electrons: On the other hand, losing four electrons would require a significant amount of energy as the four valence electrons are relatively close to the nucleus and strongly attracted to it. Overcoming this attraction would require substantial energy input.

• Due to these limitations, carbon forms covalent bonds by sharing its valence electrons with other atoms. 
• Covalent bonds are formed in compounds involving carbon, where atoms share electrons to achieve a more stable electron configuration.

Ionic compounds have the ability to conduct electricity when dissolved in water or in a molten state due to the presence of ions that can move and carry electric charges. In contrast, carbon compounds are generally poor conductors of electricity. This is because covalent compounds do not dissociate into ions in solution and do not have freely moving charged particles that can conduct electricity.

Question 2. Explain why carbon cannot form C₄⁺ cations or C₄^- anions, but instead forms covalent compounds. Additionally, provide reasons to explain why covalent compounds are (i) poor conductors of electricity and (ii) have low melting and boiling points. (Delhi 2014)

Ans. Carbon cannot form C₄⁺ cations or C₄^- anions because it would require a significant amount of energy to remove or gain four electrons from its outermost shell. 

• Carbon has a total of four valence electrons, and its atomic structure does not favor the formation of stable cations or anions.
• Covalent compounds, on the other hand, are formed when atoms share electrons in order to achieve a more stable electron configuration. 
• The reasons why covalent compounds exhibit certain characteristics are as follows:

(i) Covalent compounds are bad conductors of electricity because they do not contain freely moving charged particles.

•  In covalent compounds, electrons are shared between atoms rather than transferred to form ions. 
• As a result, there are no mobile ions or charged species that can carry an electric current.

(ii) Covalent compounds have low melting and boiling points compared to ionic compounds. 

• This is because the intermolecular forces in covalent compounds, such as van der Waals forces or dipole-dipole interactions, are relatively weak. 
• These forces are easily overcome by applying heat, resulting in the lower energy required to break the bonds between covalent molecules, hence the lower melting and boiling points.

Question 3. Provide the chemical equations to illustrate the reactions that occur when:

(i) Sodium hydroxide is combined with ethanoic acid.

(ii) Solid sodium hydrogen carbonate is mixed with ethanoic acid.

(iii) Ethanol undergoes a reaction with sodium. (Foreign 2014)

Ans. (i) When sodium hydroxide is added to ethanoic acid, a neutralization reaction occurs. By referring to the following chemical equation, the reaction can be understood:

CH₃COOH + NaOH → CH₃COONa + H₂O

In this reaction, the sodium hydroxide (NaOH) reacts with ethanoic acid (CH₃COOH) to form sodium acetate (CH₃COONa) and water (H₂O). 

• The sodium hydroxide provides the hydroxide ions (OH^-) which react with the hydrogen ions (H⁺) from the ethanoic acid to form water. 
• The sodium cation (Na+) from the sodium hydroxide combines with the acetate anion (CH₃COO^-) from the ethanoic acid to form sodium acetate, which is a salt.

(ii) When solid sodium hydrogen carbonate (NaHCO₃), also known as baking soda, is added to ethanoic acid, a double displacement reaction occurs. By referring to the following chemical equation, the reaction can be understood:

CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

• In this reaction, the sodium hydrogen carbonate reacts with ethanoic acid to produce sodium acetate, water, and carbon dioxide gas. 
• The carbon dioxide gas is released as bubbles, giving the reaction a fizzy or effervescent nature. 
• This reaction is commonly used in baking, where the carbon dioxide gas produced helps dough rise.

(iii) When ethanol (C₂H₅OH) reacts with sodium (Na), a single displacement reaction occurs. By referring to the following chemical equation, the reaction can be understood:

C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

In this reaction, the sodium (Na) displaces the hydrogen (H) from the ethanol molecule, resulting in the formation of sodium ethoxide (C₂H₅ONa) and hydrogen gas (H₂). 

• Sodium ethoxide is a salt-like compound formed by the reaction of sodium with ethanol.
• It is important to note that these reactions are simplified representations and may occur in different steps or under specific reaction conditions. 
• The actual reaction mechanisms and conditions can vary depending on factors such as temperature, concentration, and the presence of catalysts.

---

Previous Year Questions

1. Extraction of metal from the ore cassiterite involves...[JEE Advanced 2011]
2. Commonly used vectors for human genome sequencing are...[NEET UG 2014]
3. Interfascicular cambium and cork cambium are formed due to​..
4. Pneumotaxic centre is present in​...[UP CPMT 2007]
5. Reaction of HBr with propene in the presence of peroxide gives….[NEET UG 2004]
6. Assuming the expression for the pressure exerted by the gas on the walls of the container, it can be shown that pressure is...[MHT CET 2016]
7. Which among the following is the strongest acid?...[TS EAMCET 2017]
8. Isopropyl alcohol on oxidation forms​..
9. A vector is not changed if​..
10. Which of the following arrangements does not represent the correct order of the property stated against it?...[JEE Main 2013]

For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates

---

Check-Out: