(SEM II) THEORY EXAMINATION 2024-25 ENGINEERING CHEMISTRY

B.Tech (Semester II) Theory Examination 2024–25

Maximum Marks: 70 | Time: 3 Hours

This question paper evaluates students’ understanding of Engineering Chemistry concepts including molecular orbital theory, spectroscopy, corrosion, water treatment, polymers, green chemistry, batteries, cement, fuels, calorimetry, and organic reaction mechanisms. The paper is divided into three sections: A, B, and C.

SECTION A — Short Answer Questions (Q1a–Q1g)

[Total 14 Marks | 2 Marks Each]

This section tests basic definitions, concepts, and small numerical calculations.

Q1(a)

Arrange O₂, O₂⁺⁺, and O₂²⁻ in increasing order of bond length based on molecular orbital theory.

Q1(b)

Number of NMR signals expected in:
– CH₃–CH₂–CH₂Br
– CH₃–O–CH₃

Q1(c)

Reason for corrosion of the part of a nail that is inside the wood.

Q1(d)

Why zeolite softener is not recommended for feed water in high-pressure boilers.

Q1(e)

Why ethane (C₂H₆) cannot polymerise but ethene (C₂H₄) forms polymers.

Q1(f)

Explain why F₂ is diamagnetic and O₂ is paramagnetic using MO diagrams.

Q1(g)

Calculate the hardness of water containing Ca(HCO₃)₂ = 81 mg/L in ppm and °Fr.

This section checks clarity of concepts from MO theory, spectroscopy, polymerisation, corrosion, water chemistry, and numericals.

SECTION B — Descriptive Questions (Attempt Any 3)

[21 Marks | 7 Marks Each]

Q2(a)

Draw MO diagram of HF molecule and calculate bond order.

Q2(b)

Identify IR active molecules among H₂, HCl, CO₂, H₂O.
Explain types of vibrational modes in CO₂ (asymmetric, symmetric stretch, and bending).

Q2(c)

Explain corrosion of a metal rod half-immersed in water – concept of differential aeration cell.

Q2(d)

Explain Lime–Soda process, with:

Advantages

Limitations

Numerical: Calculate lime & soda required for 10,000 L water with given impurities.

Q2(e)

Define conducting polymers.
Identify polymer used in touch screens.
Write advantages and limitations of conducting polymers.

This section tests knowledge of water treatment, spectroscopy, corrosion cells, polymer chemistry, and numerical applications.

SECTION C — Long Answer Questions (Q3 to Q7)

[35 Marks | Attempt 1 Part from Each Question | 7 marks each]

Q3 – Green Chemistry / MO Theory

Q3(a)

Explain five principles of Green Chemistry.
Describe green synthesis of Paracetamol.

Q3(b)

Given an XY₂ molecule with bond order = 2.5, draw possible MO energy level diagram, electronic configuration, and explain its magnetic nature (diamagnetic/paramagnetic).

Q4 – Stereochemistry / NMR Spectroscopy

Q4(a)

Explain why:

Even number of cumulative double bonds → optical isomerism

Odd number → geometrical isomerism
Give proper reasons.

Q4(b)

Why TMS (Tetramethylsilane) is used as reference in NMR?
Give number of ¹H-NMR signals and splitting patterns for:
(i) (CH₃)₃COCH₃
(ii) CH₃CH(Cl)CH₂Cl
(iii) CH₃COOH
(iv) C₆H₅OH

Q5 – Batteries / Cement

Q5(a)

Construction and chemistry of charging & discharging of Lead-acid battery.

Q5(b)

Constituents of cement.
Explain manufacturing, setting, and hardening mechanism.

Q6 – Fuels / Water Hardness

Q6(a)

Explain parameters in proximate analysis of coal.
Bomb calorimeter numerical: Calculate GCV & NCV.

Q6(b)

Explain how scales form in boilers.
Give four disadvantages.
Numerical: Calculate hardness of 10,000 L water after zeolite softener regeneration.

Q7 – Organometallic Chemistry / Polymers

Q7(a)

Define organometallic compounds.
Preparation of Grignard reagent.
Write reactions of CH₃CH₂MgBr with:
– HCHO
– CH₃CHO
– CH₃COCH₃

Q7(b)

Define Vulcanization of rubber.
Preparation & uses of any 3 polymers:

Nylon-6,6

Bakelite

BUNA-N

Neoprene

Teflon