BT-101 Engineering Chemistry - Dec 2023 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
   aDiscuss the zeolite process for softening of water.
   How to answer

   • Principle of zeolite / permutit process with chemical reactions
   • Process schematic diagram showing bed, hard water inlet, soft water outlet, brine tank
   • Regeneration of exhausted zeolite with 10% NaCl solution
   • Advantages and limitations of the process
2. 7 Marks
   b100 ml of a water sample required 18 ml of standard EDTA solution. 20 ml of standard $\text{CaCO}_3$ (15g/L) solution required 25 ml of EDTA solution. 100 ml of the sample after boiling required 12 ml of EDTA solution. Calculate the temporary and permanent hardness of the sample.
   How to answer

   • Calculate strength of standard $\text{CaCO}_3$ solution in mg/ml
   • Calculate 1 ml of EDTA equivalence in mg of $\text{CaCO}_3$
   • Calculate Total Hardness from titration with 100 ml raw sample
   • Calculate Permanent Hardness from titration with 100 ml boiled sample
   • Determine Temporary Hardness by subtracting permanent from total hardness
3. 7 Marks
   aHow is water softened by the lime-soda process? What are its advantages?
   How to answer

   • Principle of lime-soda process and role of hydrated lime $\text{Ca(OH)}_2$ and soda ash $\text{Na}_2\text{CO}_3$
   • Chemical reactions involved in removing temporary and permanent hardness
   • Comparison/brief mention of cold and hot lime-soda processes
   • Key advantages: economical, reduces iron/manganese, increases pH/reduces corrosion
4. 7 Marks
   bGive a detailed account on the following: i) Caustic embrittlement ii) Boiler corrosion
   How to answer

   • Caustic embrittlement: formation of $\text{NaOH}$ from $\text{Na}_2\text{CO}_3$, concentration in boiler crevices/hairline cracks, stress corrosion cracking, prevention using sodium phosphate or tannin/lignin
   • Boiler corrosion: causes (dissolved oxygen, dissolved $\text{CO}_2$, dissolved mineral salts/acidic salts)
   • Reactions involved and methods of prevention (chemical/mechanical deaeration)
5. 14 Marks
   What is Lubricant? With the help of neat diagrams, explain the following criteria of lubricants: i) Viscosity index ii) Flash and fire point
   How to answer

   • Definition and classification/functions of lubricants
   • Viscosity index: definition, formula $\text{VI} = \frac{L - U}{L - H} \times 100$, and viscosity-temperature plot
   • Flash and fire point: definitions, significance, and sketch of apparatus (e.g. Pensky-Martens or Cleveland apparatus)
6. 7 Marks
   aExplain the preparation, properties and uses of Bakelite.
   How to answer

   • Chemical reaction of phenol and formaldehyde under acidic/basic catalyst
   • Formation of Novolac and subsequent cross-linking to form Bakelite (cross-linked 3D network structure)
   • Properties: rigid, hard, excellent electrical insulator, chemical resistant
   • Uses: electrical switches, plugs, handles of cookware, brake linings
7. 7 Marks
   bWrite a short note on synthetic rubber with a suitable example.
   How to answer

   • Definition of synthetic rubber / elastomer
   • Example (e.g., Neoprene, Buna-S, or Buna-N)
   • Preparation reaction of chosen example from its monomers
   • Properties and applications of the example
8. 7 Marks
   aWhat is meant by a phase diagram? Explain two-component system by taking Cu-Ag system as an example.
   How to answer

   • Definition of phase diagram and reduced phase rule $F' = C - P + 1$
   • Sketch of Cu-Ag simple eutectic phase diagram showing liquidus curves, solidus line, and eutectic point
   • Discussion of phases, eutectic temperature, and eutectic composition (71.9% Ag, 28.1% Cu at 779 °C)
   • Degrees of freedom at various areas, lines, and the eutectic point
9. 7 Marks
   bHow do you explain electro negativity, ionic sizes and electron affinity of s, p - block elements?
   How to answer

   • Definition of electronegativity, ionic size, and electron affinity
   • Trends across periods and down groups for s-block elements
   • Trends across periods and down groups for p-block elements
   • Factors influencing these trends: nuclear charge, shielding effect, and atomic radius
10. 7 Marks
    aState and explain beer-Lambert's Law.
    How to answer

    • Statement of Lambert's Law and Beer's Law
    • Derivation combining both laws: $A = \epsilon \cdot c \cdot l$
    • Definition of terms: $A$ (absorbance), $\epsilon$ (molar extinction coefficient), $c$ (concentration), $l$ (path length)
    • Limitations of Beer-Lambert law
11. 7 Marks
    bDefine the following terms: i) Bathochromic shift ii) Hypsochromic shift iii) Hyperchromic shift iv) Chomophore
    How to answer

    • Bathochromic shift (Red shift): shift of absorption maximum ($\lambda_{\max}$) towards longer wavelength
    • Hypsochromic shift (Blue shift): shift of $\lambda_{\max}$ towards shorter wavelength
    • Hyperchromic shift: increase in absorption intensity ($\epsilon_{\max}$)
    • Chromophore: covalently unsaturated group responsible for electronic absorption (color generation)
12. 14 Marks
    What is periodic Table? Write trends of following in a group and in a period giving suitable reason: i) Ionic size ii) Electro negativity iii) Electro affinity
    How to answer

    • Definition of modern periodic table based on Moseley's periodic law
    • Ionic size: variation down a group (increases) and across a period (decreases) with reasons (effective nuclear charge, number of shells)
    • Electronegativity: variation along period and down group with reasons
    • Electron affinity: trends across a period (increases) and down a group (decreases) with reasons
13. 14 Marks
    Write brief note on (Any two) i) Alkalinity ii) Scales and sludge's iii) Triple point iv) Urea- formaldehyde
    How to answer

    • Alkalinity: causes ($\text{OH}^-$, $\text{CO}_3^{2-}$, $\text{HCO}_3^-$) and phenolphthalein/methyl orange titration method
    • Scales and sludges: definitions, formation in boilers, differences, prevention methods
    • Triple point: condition of temperature and pressure at which solid, liquid, and gas phases coexist in equilibrium (water phase diagram example)
    • Urea-formaldehyde resin: synthesis, condensation reaction, properties, and applications as adhesives and plastics