Carbon and Its Compounds – Solved Board Questions & NCERT Exercises
Solved CBSE board questions for Carbon and Its Compounds Class 10 Chemistry. Functional groups, reactions, soaps, and IUPAC naming practice.
Carbon and Its Compounds — Solved Board Questions
Section A: Very Short Answer (1 Mark)
Q1. What is the general formula of alkenes?
Answer
The general formula of alkenes is CₙH₂ₙ, where n ≥ 2.
Q2. Name the functional group present in ethanol.
Answer
The functional group present in ethanol is the hydroxyl group (–OH).
Q3. What is the valency of carbon?
Answer
The valency of carbon is 4 (tetravalent), as it has 4 electrons in its outermost shell that it shares to form covalent bonds.
Q4. What are hydrocarbons?
Answer
Hydrocarbons are organic compounds composed of only carbon and hydrogen atoms. Examples: methane (CH₄), ethene (C₂H₄).
Section B: Short Answer (2-3 Marks)
Q5. Differentiate between saturated and unsaturated hydrocarbons with examples.
Answer
| Saturated Hydrocarbons | Unsaturated Hydrocarbons |
|---|---|
| Contain only single bonds (C–C) | Contain double (C=C) or triple (C≡C) bonds |
| Undergo substitution reactions | Undergo addition reactions |
| Burn with a clean blue flame | Burn with a yellow sooty flame |
| Example: Ethane (C₂H₆) | Example: Ethene (C₂H₄), Ethyne (C₂H₂) |
Q6. What is a homologous series? State two characteristics.
Answer
A homologous series is a family of organic compounds having the same functional group and similar chemical properties, where successive members differ by a –CH₂– unit.
Two characteristics:
- All members can be represented by the same general formula (e.g., CₙH₂ₙ₊₂ for alkanes).
- The difference in molecular mass between two successive members is always 14 u (one –CH₂– unit).
Q7. Write the chemical equation for the reaction of ethanoic acid with sodium bicarbonate. What is observed?
Answer
Observation: Brisk effervescence is observed due to the evolution of CO₂ gas. This is a standard test to detect carboxylic acids.
Q8. Explain with a diagram how a soap micelle is formed and how it helps in cleaning.
Answer
A soap molecule has a hydrophobic (water-hating) hydrocarbon tail and a hydrophilic (water-loving) ionic head (–COO⁻Na⁺).
When soap is dissolved in water near a greasy surface:
- The hydrophobic tails of soap molecules penetrate into the grease/oil.
- The hydrophilic heads remain in the water.
- This forms a spherical aggregate called a micelle, with grease trapped at the centre.
- The micelle is soluble in water and gets washed away, carrying the dirt with it.
Section C: Long Answer (5 Marks)
Q9. (a) What are the two properties of carbon that lead to a large number of compounds? (b) Name the following compounds: CH₃OH, CH₃COOH, HCHO (c) Write one use of each.
Answer
(a) The two properties are:
- Catenation: The ability of carbon atoms to form bonds with other carbon atoms, creating chains, branches, and rings of varying lengths.
- Tetravalency: Since carbon has a valency of 4, it can bond with four other atoms (including other carbon atoms) simultaneously, leading to diverse molecular structures.
(b) and (c):
- CH₃OH — Methanol (Methyl alcohol). Use: As an industrial solvent and in the production of formaldehyde.
- CH₃COOH — Ethanoic acid (Acetic acid). Use: In food preservation (vinegar) and as a laboratory reagent.
- HCHO — Methanal (Formaldehyde). Use: As a preservative for biological specimens (formalin is a 40% aqueous solution).
Indexed Topics & Examination Keywords
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