BT101 (GS) – Engineering Chemistry
Q.1 (a) Hardness of Water
Hardness of water is the property due to the presence of dissolved salts of calcium and magnesium which prevents water from producing lather with soap.
Types of Hardness
- Temporary Hardness
- Permanent Hardness
Units of Hardness
- 1 ppm = 1 mg/L
- 1 ppm = 0.1 °Fr
- 1 ppm = 0.07 °Cl
- 1 °Cl = 14.3 ppm
- 1 °Cl = 1.433 °Fr
Why EDTA Method is Preferred?
- Accurate results.
- Single titration for Ca and Mg.
- Sharp colour change.
- Simple and economical method.
- Suitable for wide hardness range.
Q.1 (b) Principle of EDTA Titration
EDTA forms a stable colourless complex with calcium and magnesium ions at pH 10 using NH4Cl-NH4OH buffer solution.
Colour change:
Wine Red → Blue
Calculation Table
| Salt | Concentration (mg/L) | CaCO3 Equivalent |
|---|---|---|
| Ca(HCO3)2 | 16.2 | 10 |
| Mg(HCO3)2 | 7.3 | 5 |
| MgCl2 | 9.5 | 10 |
| CaSO4 | 13.6 | 10 |
| Total Hardness | 35 ppm | |
Q.2 (a) Zeolite vs Ion Exchange Process
| Feature | Zeolite Process | Ion Exchange Process |
|---|---|---|
| Principle | Na+ exchange | Complete demineralization |
| Hardness Removal | Temporary & Permanent | All dissolved salts |
| Residual Hardness | 10 ppm | 0-2 ppm |
| Regeneration | NaCl | HCl / NaOH |
Advantages for High Pressure Boilers
- Produces almost pure water.
- Prevents scaling and corrosion.
- Suitable for high pressure boilers.
- Removes both cations and anions.
Q.2 (b) Reverse Osmosis
Desalination is the process of removing dissolved salts from saline water.
In Reverse Osmosis, pressure greater than osmotic pressure is applied on saline water which forces pure water to pass through a semi-permeable membrane.
Applications
- Drinking water plants.
- Power plant boiler feed water.
- Pharmaceutical industries.
- Food processing industries.
Q.3 (a) Periodic Table Trends
| Property | Down Group | Across Period |
|---|---|---|
| Electronegativity | Decreases | Increases |
| Electron Affinity | Decreases | Increases |
| Atomic Size | Increases | Decreases |
Q.3 (b) Short Notes
Effective Nuclear Charge
Zeff = Z – S
Higher Zeff results in smaller atomic size and higher ionization energy.
Polarizability
Polarizability is the ease with which the electron cloud of an atom or ion can be distorted.
Q.4 (a) Polymerization
Addition Polymerization
- Initiation
- Propagation
- Termination
Example:
n(CH2=CH2) → (-CH2-CH2-)n
Condensation Polymerization
Two multifunctional monomers react with elimination of small molecules such as water or HCl.
Example: PET (Terylene)
Functionality of Monomer
Number of reactive sites present in a monomer molecule.
Q.4 (b) Engineering Polymers
Bakelite
- Excellent electrical insulator.
- Heat resistant.
- Used in switches and plug sockets.
PMMA (Acrylic Glass)
- Highly transparent.
- Lightweight.
- Used in aircraft windows and lenses.
Neoprene
- Oil and chemical resistant.
- Good weather resistance.
- Used in hoses and cable insulation.
RGPV B.Tech I Semester (Group A) — SGPA Calculator
CS, IT, EE, EX, EI, FT, AT, MI, BT & BM branches | New Scheme W.E.F. July 2018
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