Question

What are hydrocarbons ?

Answer 1

Step 1: Understanding the term "hydrocarbons":
The term "hydrocarbon" is derived from "hydro" (hydrogen) and "carbon" (carbon atoms).

Step 2: Composition of hydrocarbons:
Hydrocarbons are organic compounds composed exclusively of:
- Carbon (C)
- Hydrogen (H)
These elements form a wide array of compounds through various bonding arrangements.

Step 3: Types of hydrocarbons:
Hydrocarbons are primarily categorized as:
- Alkanes: Saturated hydrocarbons with single bonds (e.g., methane CH₄)
- Alkenes: Unsaturated hydrocarbons with at least one double bond (e.g., ethene C₂H₄)
- Alkynes: Unsaturated hydrocarbons with at least one triple bond (e.g., ethyne C₂H₂)
- Aromatic hydrocarbons: Compounds featuring a benzene ring structure (e.g., benzene C₆H₆)

Step 4: Conclusion:

Hydrocarbons are organic compounds comprising only carbon and hydrogen.

Answer 2

Step 1: Why Carbon Forms Many Compounds:
Carbon's ability to form millions of compounds stems from two key properties.

Step 2: Property 1 – Tetravalency:
- Carbon (atomic number 6) has an electronic configuration of 2, 4.
- With 4 valence electrons, it requires 4 more to achieve a full octet.
- Consequently, carbon forms four covalent bonds with atoms like hydrogen, oxygen, nitrogen, or other carbon atoms.
- This tetravalency enables the formation of diverse and stable molecular structures.

Step 3: Property 2 – Catenation:
- Carbon atoms can link to one another, creating long chains, branched structures, or rings.
- This characteristic is termed catenation.
- The robust and stable carbon-carbon bonds facilitate the construction of extensive and intricate molecules, including hydrocarbons, proteins, and DNA.

Step 4: Summary of Properties:
Carbon's extensive compound formation is attributed to:
1. Tetravalency: The capacity to form four covalent bonds.
2. Catenation: The capability to form strong covalent bonds with itself, resulting in chains and complex architectures.

Answer 3

Step 1: Functional Groups in Aldehydes and Ketones:
1. Aldehydes possess the aldehyde group (-CHO).
   Example: Formaldehyde (H–CHO), Acetaldehyde (CH₃–CHO)

2. Ketones contain the ketone group (>C=O), also represented as (-CO-).
    Example: Propanone (CH₃–CO–CH₃)

Step 2: Reaction Between Ethanoic Acid and Ethanol:
- Ethanoic acid: CH₃COOH
- Ethanol: C₂H₅OH
- Catalyst: Concentrated H₂SO₄ (sulfuric acid)
- This reaction is classified as esterification.

Step 3: Chemical Equation:
CH₃COOH + C₂H₅OH  $\xrightarrow{\text{conc. H}_2\text{SO}_4}$  CH₃COOC₂H₅ + H₂O
(Ethanoic acid + Ethanol → Ethyl ethanoate + Water)

Step 4: Conclusion:
- The functional group of aldehydes is –CHO.
- The functional group of ketones is >C=O.
- Under the influence of concentrated sulfuric acid, ethanoic acid reacts with ethanol to yield an ester, specifically ethyl ethanoate, and water. This process exemplifies esterification.

Answer 4

Step 1: Define Structural Isomers:
Structural isomers are compounds sharing the identical molecular formula but differing in their structural formula. This indicates an equal quantity and type of atoms, arranged distinctively within the molecular structure.

Step 2: Butane's Molecular Formula:
The molecular formula for butane is C₄H₁₀.
It possesses two structural isomers due to the varied arrangements of its carbon atoms, while the molecular formula remains constant.

Step 3: Structure of the First Isomer – n-Butane:
In n-butane, the carbon atoms are arranged in a linear configuration:
CH₃–CH₂–CH₂–CH₃
This represents a straight-chain structure without any branching.

Step 4: Structure of the Second Isomer – Isobutane (Methylpropane):
Isobutane features a branched arrangement of carbon atoms, with a branch occurring at the second carbon atom:
CH₃–CH(CH₃)–CH₃
This can also be depicted as a branched structure (as illustrated in the accompanying image).

Step 5: Conclusion:
The two structural isomers of butane (C₄H₁₀) are:
1. n-Butane: CH₃–CH₂–CH₂–CH₃
2. Isobutane (Methylpropane): CH₃–CH(CH₃)–CH₃
These are classified as structural isomers due to their identical molecular formulas but distinct structural arrangements.