BT-101 Engineering Chemistry - Dec 2024 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 Temporary and Permanent hardness water, How it is differentiate? Give suitable examples.
   How to answer

   • Definition of temporary hardness (carbonate hardness) caused by bicarbonates of Ca and Mg
   • Definition of permanent hardness (non-carbonate hardness) caused by chlorides, sulfates of Ca and Mg
   • Methods of removal (boiling vs chemical treatment / ion exchange)
   • Key differences tabulated
   • Representative chemical formulas and examples
2. 7 Marks
   bWrite a note on scales and sludges.
   How to answer

   • Definition of sludges (loose, slimy precipitates like MgCO3, MgCl2)
   • Definition of scales (hard, adherent coating like CaSO4, silicates)
   • Disadvantages caused (fuel wastage, overheating, danger of explosion)
   • Prevention and removal methods (blow-down, internal/external conditioning)
3. 7 Marks
   aExplain Ion-exchange process of water softening with neat diagram.
   How to answer

   • Principle of ion-exchange (demineralization/deionization)
   • Cation exchanger reactions ($RH_2 + Ca^{2+} \rightarrow RCa + 2H^+$)
   • Anion exchanger reactions ($R'(OH)_2 + SO_4^{2-} \rightarrow R'SO_4 + 2OH^-$)
   • Regeneration of exhausted resins using dilute acid and dilute alkali
   • Neat schematic diagram of cation and anion exchange columns
4. 7 Marks
   bWhat are boiler troubles? How are they caused? Suggest steps for minimizing the boiler troubles.
   How to answer

   • Definition of boiler troubles (problems arising from using hard/impure water in boilers)
   • Types and causes: Scales/sludges, Priming & Foaming, Caustic embrittlement, Boiler corrosion
   • Mechanisms of each boiler trouble
   • Remedial measures and prevention steps (water softening, blow-down operation, addition of antifoaming agents, phosphate conditioning)
5. 7 Marks
   aGive short note on mechanism thick film of lubrication process.
   How to answer

   • Definition of hydrodynamic / thick film lubrication
   • Mechanism: complete separation of moving metallic surfaces by thick fluid lubricant layer (at least 1000 Å)
   • Role of viscosity of lubricant and fluid shear resistance
   • Diagram showing shaft/journal rotating inside a bearing with fluid wedge
   • Typical engineering applications (delicate instruments, light/heavy journal bearings)
6. 7 Marks
   bExplain about flash and fire point and their significance.
   How to answer

   • Definition of flash point (lowest temperature at which oil gives off sufficient vapors to ignite momentarily with a flash)
   • Definition of fire point (lowest temperature at which vapors burn continuously for at least 5 seconds)
   • Experimental determination apparatus (e.g., Pensky-Martens or Cleveland open cup)
   • Significance: safety guide in storage, transport, handling, and operation of lubricants under high operating temperatures
7. 7 Marks
   aWhat are polymers? Give their classification with examples.
   How to answer

   • Definition of polymers and repeating monomer units
   • Classification based on source: Natural, Semi-synthetic, Synthetic (with examples)
   • Classification based on structure: Linear, Branched, Cross-linked
   • Classification based on molecular forces: Elastomers, Fibers, Thermoplastics, Thermosetting plastics
   • Classification based on mode of synthesis: Addition vs Condensation polymers
8. 7 Marks
   bGive preparation, properties and uses of Bakelite.
   How to answer

   • Monomers: Phenol and Formaldehyde
   • Preparation steps: Acid/base catalyzed reaction forming o- and p-hydroxybenzyl alcohols, formation of Novolac, cross-linking with hexamethylenetetramine to form thermoset Bakelite
   • Chemical reaction equations showing cross-linked structure
   • Key properties: rigid, scratch-resistant, electrical insulator, chemical resistant
   • Important uses: electrical switches, plugs, handles of utensils, laminates
9. 7 Marks
   aWhat is oxidation corrosion and how does it take place? Describe the mechanism of oxidation corrosion.
   How to answer

   • Definition of oxidation corrosion (dry corrosion occurring by direct action of atmospheric oxygen on metals)
   • Mechanism: Oxidation of metal ($M \rightarrow M^{n+} + ne^-$) and reduction of oxygen ($O_2 + 4e^- \rightarrow 2O^{2-}$)
   • Formation of metal oxide film at the surface
   • Pilling-Bedworth ratio and types of oxide films formed (stable/protective, unstable, volatile, porous non-protective)
10. 7 Marks
    bExplain water line corrosion and galvanic corrosion.
    How to answer

    • Explanation of waterline corrosion as a case of differential aeration corrosion (metal just below meniscus is less aerated and becomes anodic)
    • Reactions and damage just below water level in steel tanks and ships
    • Explanation of galvanic corrosion (contact between two dissimilar metals in conductive medium)
    • Metal higher in electrochemical series acts as anode and corrodes preferentially
    • Examples and methods of prevention for both types
11. 14 Marks
    What is 'spectroscopy'? Discuss about Ultra -violet spectroscopy principle, instrumentation and applications.
    How to answer

    • Definition of spectroscopy (interaction of electromagnetic radiation with matter)
    • Principle of UV-Vis spectroscopy: electronic transitions ($\sigma \rightarrow \sigma^*$, $n \rightarrow \sigma^*$, $\pi \rightarrow \pi^*$, $n \rightarrow \pi^*$) and Beer-Lambert's law
    • Components of UV spectrophotometer: radiation source, monochromator, sample and reference cells, detector, recorder
    • Block diagram of single or double-beam UV spectrophotometer
    • Applications: detection of conjugation, functional groups/chromophores, quantitative analysis, identification of unknown compounds
12. 7 Marks
    aWrite short notes on Electro negativity variation in groups and periods.
    How to answer

    • Definition of electronegativity (tendency of an atom to attract shared pair of electrons)
    • Trend across a period: increases from left to right due to increased effective nuclear charge and decreased atomic radius
    • Trend down a group: decreases down the group due to addition of shells, increased atomic radius and screening effect
    • Examples using Halogens and second period elements (e.g. Li to F)
13. 7 Marks
    bExplain about polarisability.
    How to answer

    • Definition of polarisability (ease of distortion of an electron cloud of an atom or anion by an external electric field or cation)
    • Relationship between induced dipole moment and electric field ($\mu_{ind} = \alpha E$)
    • Factors affecting polarisability: size of anion/atom, charge on anion, electronic configuration
    • Significance in chemical bonding (Fajans' rules and covalent character in ionic compounds)
14. 14 Marks
    Write brief note on (Any two):

    1. i)Alkalinity
    2. ii)Emulsification number
    3. iii)Conducting polymers
    4. iv)Atomic and Ionic sizes
    How to answer

    • Alkalinity: Definition (measure of capacity to neutralize acids), ions causing alkalinity ($OH^-$, $CO_3^{2-}$, $HCO_3^-$), titration using phenolphthalein and methyl orange indicators
    • Emulsification number: Steam emulsion number (SEN), time in seconds for separation of an oil-water emulsion, significance in lubrication
    • Conducting polymers: Definition, conjugated $\pi$-electron backbone (polyacetylene, polyaniline), doping mechanism (p-doping and n-doping), applications in sensors and LEDs
    • Atomic and Ionic sizes: Definitions of atomic and ionic radius, trends across periods and down groups, comparison of cation and anion sizes with parent atoms