CBCS B.Sc. 1st Sem Chemistry Sample Paper BRABU Muzaffarpur

CBCS B.Sc. 1st Semester Chemistry Sample Paper Session: 2025-2029 BRABU Muzaffarpur

Here you can find CBCS B.Sc. 1st Semester Chemistry Sample Paper of Major, Minor and multidisciplinary Session: 2025-2029 BRABU Muzaffarpur

MJC 1st Semester 2025

Sample Paper

Time: 3 Hours
Full Marks: 70

Candidates are required to give their answer in their own words as far as practicable.
The figure in the margin indicate full marks.
Answer from all the groups are directed.

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Group-A
Compulsory

1. Chose the correct answer of the following 2 × 10 = 20

a. Identify the pair that represents isotones among the following-
i. ₈O¹⁶ and ₇O¹⁵
ii. ₁₂Mg²⁴ and ₁₄Si²⁸
iii. ₁₇Cl³⁷ and ₁₈Ar³⁸
iv. None of these

b. Balmer series of hydrogen spectra appears in
i. UV region
ii. Visible region
iii. IR region
iv. Microwave region

c. Anthracene is classified as
i. Aliphatic compound
ii. Aromatic compound
iii. Alkene
iv. Cycloalkane

d. Which carbocation is least stable?
i. CH₃⁺
ii. (CH₃)₂CH⁺
iii. C₆H₅⁺
iv. (CH₃)₃C⁺

e. Which of the following molecules has unpaired electrons (is paramagnetic)?
i. O₂
ii. F₂
iii. N₂
iv. CO

f. A hydrocarbon with formula C₆H₆ is-
i. Alkane
ii. Alkene
iii. Aromatic compound
iv. Cycloalkane

g. What is the bond order of superoxide ion?
i. 2.5
ii. 1.0
iii. 2.0
iv. 3.0

h. Which among the following contains a planar chiral center?
i. Cis-1,2-dichloroethene
ii. Trans-2-butene
iii. 2-chloropropane
iv. Glycine

i. Electrolysis of aqueous sodium malonate yields-
i. Propane
ii. Carbon dioxide
iii. Ethylene
iv. Acetylene

j. Compounds exhibiting optical isomerism include-
i. 2-chlorobutane
ii. 1-butanol
iii. 2-butene
iv. Butanone

Answer:
a. i. ₈O¹⁶ and ₇N¹⁵
b. ii. Visible region.
c. ii. Aromatic compound.
d. i. CH₃+.
e. i. O₂.
f. iii. Aromatic compound.
g. i. 2.5.
h. i. Cis-1,2-dichloroethene.
i. ii. Carbon dioxide.
j. i. 2-chlorobutane.

Group-B
Answer any FOUR questions of the following
5 × 4 = 20

2. Write electronic configuration for:
Mg(12), Fe(26), Br(35), Zn²⁺(30), Cr³⁺(24)

3. Define free radicals and carbanions with suitable examples.

4. Compare bond angles in CH₄ and NH₃. Which is larger and why?

5. Ethyne forms precipitate with ammoniacal silver nitrate but ethene does not. Explain.

6. State the requirements for a molecule to exhibit geometrical isomerism.

7. State Heisenberg's uncertainty principle and explain its significance in atomic structure.

Group-C
Answer any THREE questions of the following
10 × 3 = 30

8. a. Discuss the main types of orbitals (s, p, d, f) and their significance in electron arrangement.
b. State and explain Hund's rule of maximum multiplicity.

9. With the help of diagrams, explain the hybridization, structure and geometry of the following:
BF₃, NH₄⁺, PCl₅, XeF₂, SO₂

10. a. Describe Saytzeff’s and Hofmann’s rules for elimination reactions with examples.
b. Explain the mechanism of halogenation of alkanes using free radicals.

11. Write short notes on any FOUR:
a. Resonance energy
b. Diastereomers
c. Newman projections
d. Homolytic and heterolytic fission
e. Ionization energy
f. Schrodinger wave equation

12. a. Explain why the N–N bond in hydrazine is longer than in N₂ and shorter than in N₂H₄.
b. Arrange the following in decreasing order of basic strength. Justify your answer: Aniline, Methylamine, Ethylamine, Ammonia

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