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1. What are the salts responsible for permanent hardness of water? Discuss the softening of hard water by zeolite process with a neat sketch and chemical reactions involved therein.

2. (a) Discuss the construction and working principle of secondary Li-ion battery providing a block diagram. Write its cell reaction during the discharge process.

(b) How redox flow batteries are similar/different compared to a fuel cell?

Redox flow batteries (RFBs) and fuel cells are both electrochemical energy conversion devices.

Similarities

Differences

3. (a) Write a short note on differential aeration corrosion.

(b) What is pitting corrosion?

4. (a) Carbon dioxide $CO_2$ has two types of bond stretches: symmetrical and unsymmetrical. Classify each one of these stretches as IR active or IR inactive and explain your choice.

In carbon dioxide (CO₂), the molecule exhibits two primary stretching vibrations: symmetric and asymmetric. During the symmetric stretch, both oxygen atoms move in and out simultaneously and equally from the central carbon atom. Since CO₂ is a linear and nonpolar molecule, this motion does not result in any change in the overall dipole moment. As infrared (IR) spectroscopy only detects vibrations that produce a change in dipole moment, the symmetric stretch is IR inactive.

In contrast, the asymmetric stretch involves one oxygen atom moving toward the carbon atom while the other moves away. This out-of-phase motion disturbs the molecular symmetry and temporarily generates a dipole moment. Because this vibration leads to a fluctuating dipole, it interacts with infrared light and is therefore IR active.

(b) A spring is displaced by 8 cm and held in place with a force of 400 N. What is the spring constant of the spring?

To find the spring constant $k$, we use Hooke's Law:

$F = kx$

Where:

• $F$ is the force applied (400 N)
• $x$ is the displacement (8 cm = 0.08 m)
• $k$ is the spring constant (what we’re solving for)

Rearranging the formula:

$k = \frac{F}{x} = \frac{400}{0.08} = 5000 \, \text{N/m}$

The spring constant is 5000 N/m.

5. Define the term "Fuel". Discuss the classification of fuels with examples.

6. (a) What is hydrogen fuel? Discuss different types of hydrogen fuel. What are the advantages of-hydrogen fuel?

(b) Discuss hydrogen gas production by water electrolysis and natural gas reforming.

7. (a) What is glass transition temperature $T_g$? Discuss four factors that affect glass transition temperature.

(b) Why the catalytic and optical properties of nanomaterial are different from bulk material?

8. (a) What are the conditions for a polymer to be conductive? Give four examples of conductive polymers.

(b) Write the structure of the polymer obtained from methyl methacrylate. Discuss its applications.

The polymer obtained from methyl methacrylate (MMA) is called poly(methyl methacrylate), commonly abbreviated as PMMA.

The molecular structure of the repeating unit in PMMA can be represented as:

$[-\mathrm{CH_2{-}C(CH_3)(COOCH_3)}-]_n$

Here:

• The backbone consists of repeating carbon units.
• Each repeating unit contains a methyl group (-CH₃) and an ester group (-COOCH₃) attached to the main chain.

This polymer is synthesized by free-radical polymerization of the monomer methyl methacrylate (CH₂=C(CH₃)COOCH₃).

Applications of PMMA

PMMA is a transparent, rigid thermoplastic with excellent weathering and UV resistance. It is widely used in various fields:

• Substitute for glass in windows, lenses, and light covers
• Used in contact lenses and intraocular lenses due to its biocompatibility
• Windshields for motorcycles and aircraft
• Used in decorative panels and interior designs
• Used as bone cement in orthopedic surgeries

9. (i) Draw the structure of EDTA. What happens when it is added to hard water?

(ii) What are the advantages of fuel cell over battery?

Advantages

1. Fuel cells provide continuous power as long as fuel is supplied, whereas batteries need recharging after their stored energy is depleted.
2. Fuel cells produce only water and heat as by-products, making them more environmentally friendly.

(iii) Write the anode and cathode used in Li-ion battery. Write the cell reaction during charging of Li-ion battery.

(iv) What is the relation between wave number of IR absorption and the reduced mass?

The relation between the wave number of IR absorption and the reduced mass of a vibrating diatomic molecule is given by the equation derived from the harmonic oscillator model:

$\tilde{\nu} = \frac{1}{2\pi c} \sqrt{\frac{k}{\mu}}$

Where:

• $\tilde{\nu}$ is the wave number (in cm⁻¹)
• $c$ is the speed of light (in cm/s)
• $k$ is the force constant of the bond (in dyn/cm or N/m)
• $\mu$ is the reduced mass of the two atoms (in kg or g)

The reduced mass $\mu$ is calculated as:

$\mu = \frac{m_1 m_2}{m_1 + m_2}$

Where $m_1$ and $m_2$ are the masses of the two atoms.

From the equation, the wave number $\tilde{\nu}$ is inversely proportional to the square root of the reduced mass:

$\tilde{\nu} \propto \frac{1}{\sqrt{\mu}}$

(v) Write the light sources used in UV-spectrophotometer.

The common light sources used in a UV-spectrophotometer are:

1. Deuterium lamp – used for the ultraviolet (UV) region (typically 160–375 nm).
2. Tungsten-halogen lamp – used for the visible region (typically 350–2500 nm).

In modern instruments, both lamps may be combined to cover a wide spectral range from UV to visible.

(vi) Discuss different types of coal.

Coal is classified into different types based on its carbon content, calorific value, and degree of transformation (rank).

1. Peat - Lowest rank of coal with high moisture and low carbon content; not considered true coal.
2. Lignite - Also called brown coal; soft with 25-35% carbon content and low calorific value.
3. Sub-bituminous coal - Dull black coal with 35-45% carbon; used in power generation.
4. Bituminous coal - Harder coal with 45-86% carbon; widely used in industry and power plants.
5. Anthracite - Highest grade coal with over 86% carbon; hard, shiny, and high in energy output.

(vii) How does natural gas reforming produce hydrogen? How efficient is it?

(viii) Write four applications of conductive polymer.

(ix) What is quantum confinement effect?

The quantum confinement effect occurs when the size of a semiconductor material becomes so small—typically at the nanoscale—that the motion of electrons and holes is restricted to dimensions comparable to their de Broglie wavelength. This confinement alters the material’s electronic and optical properties.

(x) Which microscopic instrument used for characterisation of CNT?

To characterize carbon nanotubes (CNTs), several microscopic instruments are commonly used:

1. Transmission Electron Microscopy (TEM)

   • Used for: Imaging internal structure, number of walls (SWCNT vs. MWCNT), defects.
   • Gives atomic-resolution images of CNTs.

2. Scanning Electron Microscopy (SEM)

   • Used for: Surface morphology, alignment, length, and distribution of CNTs.
   • Less resolution than TEM, but faster and easier for surface overviews.

3. Atomic Force Microscopy (AFM)

   • Used for: Surface topology, diameter, and height profile of CNTs.
   • Can also measure mechanical properties (like stiffness) in certain modes.

4. Scanning Tunneling Microscopy (STM)

   • Used for: Surface electronic structure at atomic resolution.
   • Mostly used in research to study electronic properties of CNTs.