Vidaara.orgClass 11 · Chemistry
CodeVID-C11-12-T1-01
Assignment — Classification, Nomenclature & Isomerism
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Show all working for Sections B, C and D. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions
5 × 1 = 5 marks
1.
The bond angle in an $sp^3$ hybridised carbon is about:
- A.$90^\circ$
- B.$109.5^\circ$
- C.$120^\circ$
- D.$180^\circ$
2.
The suffix for a carboxylic acid in IUPAC naming is:
- A.-al
- B.-one
- C.-oic acid
- D.-ol
3.
Successive members of a homologous series differ by:
- A.$CH_3$
- B.$CH_2$
- C.$C_2H_4$
- D.$CH_4$
4.
The number of chain isomers of $C_5H_{12}$ is:
- A.2
- B.3
- C.4
- D.5
5.
A chiral carbon must be bonded to:
- A.two like groups
- B.three different groups
- C.four different groups
- D.one double bond
Section B — Short Answer (2 marks)
3 × 2 = 6 marks
6.
Distinguish between a condensed formula and a bond-line formula with one example each for propan-1-ol.
7.
Define functional group and homologous series.
8.
Why is the cis isomer of but-2-ene different from the trans isomer?
Section C — Short Answer (3 marks)
2 × 3 = 6 marks
9.
Give the IUPAC names of (i) $CH_3CH(Cl)CH_2CH_3$ and (ii) $CH_3COCH_2CH_3$ and (iii) $CH_2=CHCH_2CH_3$.
10.
Identify the type of isomerism in each pair: (i) propan-1-ol & propan-2-ol; (ii) ethanol & dimethyl ether; (iii) $CH_3CH_2CH_2CH_3$ & $(CH_3)_3CH$.
Section D — Long Answer (5 marks)
1 × 5 = 5 marks
11.
State the rules of IUPAC nomenclature for branched-chain compounds and apply them to name $CH_3CH(CH_3)CH(C_2H_5)CH_2CH_3$.
Answer Key
Section A — Multiple Choice Questions
- (B) $109.5^\circ$
- (C) -oic acid
- (B) $CH_2$
- (B) 3
- (C) four different groups
Section B — Short Answer (2 marks)
- Condensed: $CH_3CH_2CH_2OH$ (bonds to H omitted). Bond-line: a three-vertex zig-zag ending in $−OH$, where each vertex/end is a carbon with H understood.
- A functional group is the reactive atom/group that governs a compound's chemistry (e.g. $−OH$). A homologous series is a family with the same functional group and a constant $CH_2$ (14 u) difference between members, sharing a general formula.
- Rotation about the C=C double bond is restricted, so the two methyl groups are locked either on the same side (cis) or on opposite sides (trans), giving two distinct compounds with different physical properties.
Section C — Short Answer (3 marks)
- (i) 2-chlorobutane; (ii) butan-2-one; (iii) but-1-ene.
- (i) position isomerism; (ii) functional isomerism; (iii) chain isomerism.
Section D — Long Answer (5 marks)
- Rules: (1) select the longest chain containing the principal functional group as the parent; (2) number it to give the principal group/first substituent the lowest locant set; (3) name substituents as prefixes in alphabetical order with locants; (4) combine prefix + root + suffix, using di-/tri- for repeats. Applying to the molecule: the longest chain is 5 carbons (pentane) with a methyl on C-2 and an ethyl on C-3 — name: 3-ethyl-2-methylpentane (ethyl before methyl alphabetically).
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