BT-101 Engineering Chemistry - Nov 2022 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aWhat is the principle of EDTA method? Explain the estimation of total hardness of water by complexometric method.
   How to answer

   • Principle of EDTA titration using Eriochrome Black T indicator at pH 10
   • Formation of unstable wine-red metal-indicator complex followed by stable colourless EDTA-metal complex
   • End point colour change from wine-red to clear blue
   • Stepwise procedure and calculation formula for estimation of total hardness
2. 7 Marks
   bCalculate the total hardness of a water sample which shows following analysis : $\text{Ca(HCO}_3)_2 = 4.86\text{ mg/L}$; $\text{Mg(HCO}_3)_2 = 5.84\text{ mg/L}$; $\text{CaSO}_4 = 6.8\text{ mg/L}$ and $\text{MgSO}_4 = 8.4\text{ mg/L}$.
   How to answer

   • Formula: CaCO3 equivalent = Amount of hardness-causing salt * (50 / Equivalent weight of salt)
   • Convert Ca(HCO3)2 (MW 162, Eq. wt 81): 4.86 * (50 / 81) = 3 mg/L
   • Convert Mg(HCO3)2 (MW 146, Eq. wt 73): 5.84 * (50 / 73) = 4 mg/L
   • Convert CaSO4 (MW 136, Eq. wt 68): 6.8 * (50 / 68) = 5 mg/L
   • Convert MgSO4 (MW 120, Eq. wt 60): 8.4 * (50 / 60) = 7 mg/L
   • Total Hardness = 3 + 4 + 5 + 7 = 19 mg/L (or ppm) as CaCO3 equivalent
3. 7 Marks
   aWhat is Caustic embrittlement? How do you prevent it?
   How to answer

   • Definition of caustic embrittlement as a type of boiler corrosion / cracking at bends and joints
   • Mechanism involving decomposition of Na2CO3 to NaOH and concentration in microscopic cracks
   • Formation of galvanic cell: stressed iron (anode) vs unstressed iron (cathode)
   • Methods of prevention: adding sodium phosphate, sodium sulphate, tannin, or lignin
4. 7 Marks
   bHow is portable water disinfected by ozonation?
   How to answer

   • Definition of ozonation and its role as a powerful oxidizing disinfectant
   • Generation and decomposition of ozone: O3 -> O2 + [O] (nascent oxygen)
   • Action of nascent oxygen on bacteria and pathogens (destruction of cell walls)
   • Advantages of ozonation over chlorination (no residual taste/odor)
5. 14 Marks
   Write a note on lubricants with special reference to their (i) classification (ii) mode of action with examples and uses.
   How to answer

   • Classification of lubricants: solid, semi-solid, and liquid lubricants with examples
   • Mechanism / mode of action: hydrodynamic (fluid film), boundary, and extreme pressure lubrication
   • Examples of each class and their industrial uses
6. 7 Marks
   aWhat is the difference between free radical and ionic polymerization?
   How to answer

   • Initiators: peroxides/azo compounds vs Lewis acids/bases (electrophiles/nucleophiles)
   • Active species: neutral free radicals vs carbocations/carbanions
   • Effect of temperature and solvents
   • Termination mechanisms: coupling/disproportionation vs combination with counter-ion/solvent
7. 7 Marks
   bWrite a note on preparation, properties and uses of i) Bakelite ii) NYLON 6,6
   How to answer

   • Bakelite: Preparation from phenol and formaldehyde (Novolac and cross-linked structure), key properties (thermosetting, electrical insulator), and uses
   • Nylon 6,6: Preparation from adipic acid and hexamethylenediamine, key properties (high tensile strength, abrasion resistance), and uses (fibres, gears, ropes)
8. 14 Marks
   Differentiate the following with suitable examples. a) Galvanic series and Electrochemical series. b) Thermosettic polymers and Thermoplastic polymers.
   How to answer

   • Differences between Galvanic series (practical environments/sea water, includes alloys) and Electrochemical series (standard states/unit activity, pure metals only)
   • Differences between Thermoplastic (linear/branched, meltable, recyclable) and Thermosetting polymers (cross-linked, decompose on heating, not recyclable) with examples
9. 7 Marks
   aWhat is Spectroscopy? Describe the principle, instrumentation process of vibrational and rotational spectroscopy.
   How to answer

   • Definition of spectroscopy (interaction of EM radiation with matter)
   • Principle of rotational spectroscopy (microwave region, permanent dipole moment change required)
   • Principle of vibrational spectroscopy (infrared region, change in dipole moment during vibration)
   • Instrumentation components: radiation source, monochromator, sample cell, detector, and recorder
   • Schematic diagram of spectrometer setup
10. 7 Marks
    bExplain about Lambert and beer's law
    How to answer

    • Statement of Lambert's Law: absorbance is directly proportional to path length
    • Statement of Beer's Law: absorbance is directly proportional to concentration
    • Combined Beer-Lambert law: A = log(I0/I) = epsilon * c * l
    • Definitions of terms (molar absorptivity, path length, concentration) and limitations
11. 14 Marks
    Describe about the following: i) Zeolite process ii) ion-exchange process with neat diagram
    How to answer

    • Zeolite process: Principle, reactions with hydrated sodium aluminosilicate, and regeneration with 10% NaCl solution
    • Ion-exchange process: Cation and anion resin exchangers, reactions for removing all ions
    • Regeneration using dil. HCl and dil. NaOH
    • Labeled schematic diagram of ion-exchange demineralization plant
12. 14 Marks
    Write brief note on (Any two): i) Phase diagram of single component systems ii) Electronic transitions iii) Vibrational modes in IR spectroscopy iv) Electro negativity
    How to answer

    • Water/Sulphur system phase diagram showing triple point, curves, and degrees of freedom using Gibbs Phase Rule F = C - P + 2
    • Types of electronic transitions: sigma -> sigma*, n -> sigma*, pi -> pi*, n -> pi* with energy order
    • Fundamental IR modes: stretching (symmetric, asymmetric) and bending (scissoring, rocking, wagging, twisting) with 3N-6 / 3N-5 degrees of freedom
    • Electronegativity definition, trends across the periodic table, and scales (Pauling/Mulliken)