Worksheet on Carbon and its Compounds

Solved Questions on Carbon and its Compounds

1. Which of the following compounds is a structural isomer of pentane?

a)
b)
c)
d)

Answer: a) Option a) represents 2-methylbutane which is a structural isomer of pentane. It has the same molecular formula C₅H₁₂ but a different arrangement of carbon atoms. In 2-methylbutane, there is a branching or substituent group (methyl group, CH₃) attached to one of the carbon atoms in the pentane chain

2. In a laboratory experiment, a chemist is attempting to synthesise an ester. Which of the following combinations of reactants is most likely to produce an ester?

a) CH₃COOH (Ethanoic acid) + NaOH (Sodium hydroxide)
b) CH₃COOH (Ethanoic acid) + C₂H₅OH (Ethanol)
c) C₂H₅OH (Ethanol) + NaOH (Sodium hydroxide)
d) C₂H₅OH (Ethanol) + C₂H₄ (Ethene)

Answer: b) Esters are typically synthesised through a reaction known as esterification, where a carboxylic acid reacts with an alcohol in the presence of an acid catalyst.

In this case:
Ethanoic acid (CH₃COOH) is a carboxylic acid.
Ethanol (C₂H₅OH) is an alcohol.
The reaction between ethanoic acid and ethanol produces ethyl ethanoate (CH₃COOC₂H₅), which is an ester.

The chemical reaction is as follows: CH₃COOH (Ethanoic acid) + C₂H₅OH (Ethanol) → CH₃COOC₂H₅ (Ethyl ethanoate, an ester) + H₂O (Water)

3. A researcher is studying the solubility of various organic compounds in water. Which functional group in a molecule is most likely to increase its water solubility?

a. Hydroxyl (-OH)
b. Carbonyl (C=O)
c. Carboxyl (-COOH)
d. Alkyl (C-C)

Answer: a) The functional group that is most likely to increase the water solubility of a molecule is the hydroxyl (-OH) group. This is because the hydroxyl group can form hydrogen bonds with water molecules. Hydrogen bonds are relatively strong intermolecular forces that help molecules dissolve in water. When a molecule contains a hydroxyl group, it can readily interact with water molecules, leading to improved solubility.

4. In a region with very hard water, residents often complain about soap scum buildup in bathtubs and on glass surfaces. Explain the chemical process behind soap scum formation when using soap in hard water.

a) Soap reacts with calcium ions to form insoluble calcium carbonate.
b) Soap reacts with magnesium ions to form a sticky residue.
c) Soap reacts with sodium ions to create a slippery surface.
d) Soap reacts with chloride ions to produce a foamy lather.

Answer: a) Soap scum formation in hard water occurs due to a chemical reaction between the soap (which is typically a sodium or potassium salt of a long-chain fatty acid) and the calcium ions (Ca²⁺) present in hard water. Hard water contains high concentrations of calcium and magnesium ions.

5. Which allotrope of carbon is characterised by the following properties?

I. Composed of a single layer of carbon atoms.
II. Has excellent electrical conductivity.
III. Possesses exceptional mechanical strength.
IV. Forms a hexagonal lattice structure.

a) Graphite
b) Diamond
c) Graphene
d) Buckminsterfullerene

Answer: c) Graphene, among the carbon allotropes mentioned, is characterised by a single layer of carbon atoms arranged in a hexagonal lattice. It possesses excellent electrical conductivity due to delocalised electrons and exceptional mechanical strength. These properties make it unique and suitable for a range of applications.

FAQs

1. How does carbon bond with other elements to form compounds?

Carbon forms covalent bonds with other elements, sharing electrons to achieve stability. This bonding versatility enables carbon to create a wide range of compounds, from simple hydrocarbons to complex biomolecules.

2. What are hydrocarbons, and how are they classified?

Hydrocarbons are solely hydrogen and carbon compounds. The kind of carbon-carbon bonds that are present in their structures determines which grouping of compounds they belong to: alkanes, alkenes, and alkynes.

3. What are the key properties and uses of carbon dioxide?

Carbon dioxide is a colourless gas with properties that contribute to climate regulation. It is important for photosynthesis, but excessive emissions can lead to environmental concerns such as global warming.

4. What is the importance of carbon cycles in ecosystems?

The transfer of carbon through several activities, including photosynthesis, respiration, and decomposition, is known as the carbon cycle. Maintaining ecological balance and ecosystem health requires an understanding of these cycles.

5. What is the role of carbon compounds in the formation of fossil fuels?

Coal, oil, and natural gas are examples of fossil fuels. These materials are generated from carbon-rich biological matter that has been buried and changed over millions of years. These fuels are important worldwide energy sources.