Vidaara.orgClass 10 · Chemistry
CodeC10-CHEM-4-CW
Carbon and its Compounds — Chapter Worksheet
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- This is a full-length worksheet covering the whole chapter — every topic is included.
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Write balanced equations and structural formulae where asked. Show all working for Sections B, C and D.
Section A — Multiple Choice Questions
6 × 1 = 6 marks
1.
The valency of carbon is:
- A.2
- B.3
- C.4
- D.6
2.
The general formula of an alkene is:
- A.CnH2n+2
- B.CnH2n
- C.CnH2n-2
- D.CnHn
3.
The functional group in ethanoic acid is:
- A.−OH
- B.−CHO
- C.−COOH
- D.−CO−
4.
Hydrogenation of oils uses a catalyst of:
- A.iron
- B.nickel
- C.copper
- D.zinc
5.
Soaps form scum in water that is:
- A.soft
- B.hard
- C.distilled
- D.boiled
6.
The allotrope of carbon shaped like a football is:
- A.diamond
- B.graphite
- C.fullerene
- D.coke
Section B — Short Answer (2 marks)
4 × 2 = 8 marks
7.
Why does carbon form covalent and not ionic compounds?
8.
Define a homologous series and give one example.
9.
Write the equation for the combustion of ethanol.
10.
Distinguish between soap and detergent in one respect.
Section C — Short Answer (3 marks)
3 × 3 = 9 marks
11.
Explain why diamond is hard and a non-conductor, while graphite is soft and conducts electricity.
12.
Explain the cleansing action of soap using the idea of a micelle.
13.
What is esterification? Write the equation for the ester formed from ethanoic acid and ethanol.
Section D — Long Answer (5 marks)
2 × 5 = 10 marks
14.
Define combustion, oxidation, addition and substitution reactions of carbon compounds, giving one balanced equation for each.
15.
Describe the preparation idea and important properties of ethanoic acid, including its reaction with sodium hydroxide, with sodium carbonate, and esterification with ethanol. Write balanced equations.
Answer Key
Section A — Multiple Choice Questions
- (C) 4
- (B) CnH2n
- (C) −COOH
- (B) nickel
- (B) hard
- (C) fullerene
Section B — Short Answer (2 marks)
- Carbon has 4 valence electrons; gaining or losing 4 electrons to form an ion needs too much energy, so carbon shares its electrons, forming covalent bonds.
- A homologous series is a family of compounds with the same functional group in which successive members differ by -CH2, e.g. the alcohols methanol, ethanol, propanol.
- C2H5OH + 3O2 -> 2CO2 + 3H2O + heat.
- Soap is a sodium/potassium salt of a fatty acid and forms scum in hard water; a detergent is a sulphonate/ammonium salt of a long-chain hydrocarbon and works even in hard water.
Section C — Short Answer (3 marks)
- In diamond each carbon is bonded to four others in a rigid 3-D network with no free electrons, so it is hard and does not conduct. In graphite each carbon is bonded to three others in layers; the layers slide (soft) and the fourth free electron carries current (conducts).
- Soap molecules have a hydrophobic tail and a hydrophilic head. In water they form micelles with tails pointing into the oily dirt and heads facing the water. The oil is trapped inside the micelle and washed away with rinse water.
- Esterification is the reaction of a carboxylic acid with an alcohol (conc. H2SO4 catalyst) to form a sweet-smelling ester and water: CH3COOH + C2H5OH -> CH3COOC2H5 + H2O.
Section D — Long Answer (5 marks)
- Combustion: burning in oxygen to release heat and light, e.g. CH4 + 2O2 -> CO2 + 2H2O. Oxidation: an alcohol is oxidised to an acid by an oxidising agent, e.g. C2H5OH + 2[O] -> CH3COOH + H2O (alkaline KMnO4). Addition: hydrogen adds across a double bond over a Ni catalyst, e.g. C2H4 + H2 -> C2H6 (hydrogenation). Substitution: an atom replaces a hydrogen, e.g. CH4 + Cl2 -> CH3Cl + HCl in sunlight.
- Ethanoic acid (CH3COOH) is a weak acid (the acid of vinegar; pure form is glacial acetic acid). With a base: CH3COOH + NaOH -> CH3COONa + H2O (neutralisation). With a carbonate: 2CH3COOH + Na2CO3 -> 2CH3COONa + H2O + CO2 (brisk effervescence of CO2). Esterification with ethanol: CH3COOH + C2H5OH -> CH3COOC2H5 + H2O (conc. H2SO4 catalyst), giving a sweet-smelling ester used in perfumes and flavours.
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