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CBSE · Class 11 · Chemistry

Organic Chemistry – Some Basic Principles and Techniques

Standard difficulty · 20 questions · 40 marks

Name: Date: Score: ____ / 40

Show your working for Sections B and C. Answers are on the last page — try every question first!

Section A — Choose the correct answer8 × 1 = 8 marks
1.
The ability of carbon to form long chains by bonding to itself is called:
  1. isomerism
  2. resonance
  3. hybridisation
  4. catenation
2.
The IUPAC name of CH2=CHCH3 is:
  1. 2-methylpropene
  2. propan-1-amine
  3. propene
  4. 2-methylpropan-1-ol
3.
CH3CH2CHO belongs to the class:
  1. ether
  2. alkane
  3. ketone
  4. aldehyde
4.
How many structural isomers are possible for C4H8 (open-chain alkenes (ignoring cis–trans))?
  1. 5
  2. 2
  3. 3
  4. 4
5.
Propanal and propanone are:
  1. functional group isomers
  2. metamers
  3. chain isomers
  4. position isomers
6.
Which of these is an electrophile?
  1. NO2+
  2. Cl−
  3. CH3O−
  4. OH−
7.
Which shows the correct order of increasing acid strength?
  1. BrCH2COOH < ICH2COOH < ClCH2COOH
  2. ClCH2COOH < ICH2COOH < BrCH2COOH
  3. BrCH2COOH < ClCH2COOH < ICH2COOH
  4. ICH2COOH < BrCH2COOH < ClCH2COOH
8.
Assertion (A): Cl2CHCOOH is a stronger acid than Cl3CCOOH.
Reason (R): Electron-withdrawing groups stabilise the carboxylate ion by the −I effect; the effect grows with more, closer and more electronegative substituents.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, but R is true.
Section B — Short answer8 × 2 = 16 marks
9.
What is the difference between homolytic and heterolytic cleavage?
10.
3 g of an organic compound gave 6.6 g of CO2 and 3.6 g of H2O on complete combustion. Find the percentages of carbon and hydrogen in it. (2 decimal places where needed.)
11.
In a Kjeldahl estimation, the ammonia from 0.6 g of a compound neutralised 35 mL of 0.25 M H2SO4. Find the percentage of nitrogen. (2 decimal places where needed.)
12.
In a Dumas estimation, 0.25 g of a compound gave 83 mL of nitrogen at STP. Find the percentage of nitrogen. (2 decimal places where needed.)
13.
In a Carius estimation, 0.3 g of a compound gave 0.75 g of AgCl. Find the percentage of chlorine. (AgCl = 143.5 g/mol; Cl = 35.5) (2 decimal places where needed.)
14.
0.5 g of an organic compound gave 1.45 g of BaSO4 in the estimation of sulphur. Find the percentage of sulphur. (BaSO4 = 233 g/mol) (2 decimal places where needed.)
15.
In thin-layer chromatography a spot moved 6.4 cm while the solvent front moved 8 cm. Find the Rf value.
16.
Write the condensed structural formula of methoxyethane, and name its class of compound.
Section C — Word problems4 × 4 = 16 marks
17.
Explain the inductive effect, resonance effect, electromeric effect and hyperconjugation, with one example each.
18.
3.52 g of an organic compound containing C, H and O gave 7.04 g of CO2 and 2.88 g of H2O. (a) Find the percentages of C, H and O. (b) Find its empirical formula. (c) Its molar mass is 88 g/mol; find its molecular formula. (2 decimal places where needed.)
19.
(a) Classify as electrophile or nucleophile: NO2+, H+, AlCl3, CH3+, Br+. (b) Arrange these carbanions in order of increasing stability, and give the reason: (CH3)3C−, (CH3)2CH−, CH3CH2−.
20.
Write the structures and IUPAC names of all the structural isomers of C2H6O (alcohols and ethers). How many are there?
AmbifulWorksheets
Practice that never repeats
CBSE · Class 11 · Chemistry

Answer key

Organic Chemistry – Some Basic Principles and Techniques · AW-11C-OCB-2026-V1 · For parents — fold back or tear off before handing the sheet to your child.

QAnswerWorking
1(d) catenation—
2(c) propenelongest chain, lowest locants, functional group as suffix
3(d) aldehydelook at the functional group
4(c) 3but-1-ene, but-2-ene, 2-methylpropene
5(a) functional group isomers—
6(a) NO2+it is electron-deficient and accepts an electron pair
7(d) ICH2COOH < BrCH2COOH < ClCH2COOHelectron-withdrawing groups (more, closer, more electronegative) stabilise the carboxylate ion
8(d) A is false, but R is true.A is false: Cl3CCOOH is the stronger. R is true.
9In homolytic cleavage each atom keeps one electron of the bond, giving free radicals. In heterolytic cleavage one atom takes both electrons, giving a cation and an anion (for carbon, a carbocation or a carbanion).—
10C 60%; H 13.33% (it is propan-1-ol)%C = 12 × mass CO2 × 100/(44 × mass); %H = 2 × mass H2O × 100/(18 × mass)
1140.83%%N = 1.4 × molarity × 2 × volume of acid ÷ mass = 1.4 × 0.25 × 2 × 35 ÷ 0.6
1241.5%%N = 28 × 83 × 100/(22400 × 0.25)
1361.85%%X = 35.5 × 0.75 × 100/(143.5 × 0.3)
1439.83%%S = 32 × 1.45 × 100/(233 × 0.5)
150.8Rf = distance moved by substance ÷ distance moved by solvent
16CH3CH2OCH3 (ether)the root gives the chain length; suffix and locants give the group and its position
17Inductive: permanent σ-electron shift towards an electronegative atom; in CH3CH2Cl, chlorine pulls electrons from carbon. Resonance: delocalisation of π electrons or lone pairs through conjugation; in phenol the O lone pair spreads into the ring (+R). Electromeric: temporary complete π-electron shift when a reagent attacks a C=C or C=O. Hyperconjugation: delocalisation of C–H σ electrons into an adjacent empty p orbital or π bond; it makes (CH3)3C+ more stable than CH3+.—
18(a) C 54.55%, H 9.09%, O 36.36%; (b) C2H4O; (c) C4H8O2 (ethyl ethanoate)%O by difference; divide each % by its atomic mass and by the smallest; (Atomic masses: H = 1 u, C = 12 u, O = 16 u)
19(a) NO2+ electrophile; H+ electrophile; AlCl3 electrophile; CH3+ electrophile; Br+ electrophile. (b) (CH3)3C− < (CH3)2CH− < CH3CH2−: alkyl groups (+I) push electron density onto the negative carbon, so more alkyl groups destabilise it.—
202: ethanol, methoxymethane—