Que>1 Discuss the various types of chemical reactions with suitable example.
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Types of reactions:-
The good news-there are only five main types of chemical reactions
- Synthesis/Combination
A type of reaction in which an element or compound combines with another element or
compound to form a new compound
Example: 2 H2 + O2 2 H2O - Decomposition
A type of reaction in which a compound breaks down into two or more elements or
compounds
Example: CaCO3 CaO + CO2 - Combustion
A type of reaction in which a hydrocarbon reacts with oxygen to form carbon dioxide and
water
Example: C3H8 + 5O2 3CO2 + 4H2O - Single displacement
A type of reaction in which a compound and an element react to form a new element and a
new compound
Example: F2 + 2KCl Cl2 + 2KF - Double displacement
A type of reaction in which two compounds react to form two different compounds.
Example: AgNO3 + KCl AgCl + KNO3
Que>2Write a note on Standard Calomel Electrode with necessary diagram and chemical reactions.
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Standard Calomel electrode (SCE)
• The calomel electrode is most commonly used reference electrode.
• It consists of mercury, solid mercurous chloride (calomel) and a solution of KCl.
• Pure mercury is put at the bottom of the tube and is covered with a paste of mercurous chloride.
• A solution of KCl is introduced above the paste through the side tube shown on the right.
• The KCl solution also fills the side tube ending in a jet on the left.
• A platinum wire seal into a glass tube serves to make electrical contact of the electrode with the circuit.
• The half-cell whose electrode potential is to be determined is coupled with the calomel electrode through a salt bridge and the emf of the cell is measured.
• If the electrode acts as the anode the reaction is
2Hg (l) + 2Cl- – 2e- ↔ Hg2Cl2 (s)
• If it reacts as the cathode the reaction is
Hg2Cl2(s)+2e- ↔ 2Hg(l)+2Cl
Advantages of Standard Calomel Electrode:
1. It is very handy, compact and easy to transport.
2. Its potential can remain constant and it can easily be reproduced.
3. It is easy to construct and maintain.
Que>2 (OR) Explain the principle, instrumentation and working mechanism of Bomb calorimeter for the calculation of Calorific value of fuel.
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Principle:- A known amount of fuel is burnt in excess of oxygen and the heat liberated is absorbed in a known amount of water. This heat liberated is measured by noting the change in temperature.
Calorific value of the fuel is then calculated by applying the following principle:
Heat liberated by fuel = Heat absorbed by water and the calorimeter.
Construction:-
It consists of the following parts:
- Stainless Steel Bomb It consists of a long cylindrical container made up of stainless steel. It has a lid that is made air tight with the help of screws. The lid is provided with two holes for electrodes and has an oxygen inlet valve. A small ring is attached to one of the electrodes. This ring acts as a support for nickel or stainless steel crucible in which the fuel is burnt. Magnesium wire touching the fuel sample extends across the electrodes. The steel bomb is lined inside with platinum to resist corrosive action of HNO3 and H2SO4 vapors formed because of burning of fuel and is designed to withstand high pressure (25–50 atm).
- Copper Calorimeter The bomb is placed in a copper calorimeter containing a known amount of water. The calorimeter is provided with an electrical stirrer and a Beckmann thermometer that can read accurate temperature difference of up to 1/100th of a degree.
- Air Jacket and Water Jacket The copper calorimeter is surrounded by an air jacket and a water jacket to prevent loss of heat owing to radiation.
Working
· A known amount of fuel (0.5–1 g) is taken in a clean crucible supported over the ring. A fine magnesium wire, touching the fuel sample, is then stretched across the electrodes.
· About 10 mL of distilled water is introduced into the bomb to absorb vapors of sulphuric acid and nitric acid formed during combustion, and the lid of the bomb is tightly screwed.
· The bomb is filled with oxygen at 25 atmospheric pressure and placed in the copper calorimeter containing a known weight of water. The stirrer is started and the initial temperature of water is noted.
· The electrodes are then connected to a 6-volt battery to complete the circuit. The sample burns and heat is liberated. This heat is absorbed by water.
· Maximum temperature shown by the thermometer is recorded. Time taken to cool the water in the calorimeter from maximum temperature to room temperature is also noted. · The gross calorific value of the fuel is calculated as follows.
Que>3 What are the various factors affecting to the catalysis process?
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Catalysis is a process that involves the acceleration or facilitation of a chemical reaction by a substance known as a catalyst. Several factors can influence the catalysis process. Here are some of the key factors:
1)Nature of the Catalyst: The type and properties of the catalyst used can significantly affect the catalysis process. Catalysts can be heterogeneous (in a different phase than the reactants) or homogeneous (in the same phase as the reactants). The chemical composition, surface area, and surface structure of the catalyst can also impact its catalytic activity.
2)Reactant Concentration: The concentration of reactants plays a crucial role in catalysis. In some cases, an increase in reactant concentration can enhance the reaction rate by increasing the collision frequency between reactant molecules. However, in other cases, a decrease in concentration might be beneficial due to changes in the reaction mechanism.
3)Temperature: Temperature is a critical factor affecting catalysis. Generally, an increase in temperature increases the reaction rate by providing more energy to reactant molecules, resulting in more frequent and energetic collisions. However, high temperatures may also lead to catalyst deactivation or other unwanted side reactions.
4)Pressure: Pressure can influence the catalysis process, particularly for reactions involving gases. Higher pressures can increase the number of collisions between reactant molecules, leading to an increased reaction rate. However, the effect of pressure on catalysis can vary depending on the specific reaction and catalyst.
5)Surface Area: For heterogeneous catalysis, the surface area of the catalyst is crucial. A larger surface area provides more active sites for reactant molecules to adsorb and undergo reactions. Therefore, catalysts with high surface areas, such as finely divided metals or porous materials, are often preferred for efficient catalysis.
6)Presence of Catalyst Poisons: Catalyst poisons are substances that can inhibit or deactivate the catalyst, reducing its catalytic activity. These poisons can be present in the reactants or formed during the reaction. Common catalyst poisons include sulfur, lead, arsenic, and certain organic compounds.
7)Reaction Mechanism: The catalytic activity can be influenced by the specific mechanism of the reaction. Different catalysts may facilitate different reaction pathways or intermediate steps, leading to variations in the reaction rate and selectivity.
8)pH and Solvent Effects: For some catalytic reactions, the pH of the solution or the choice of solvent can significantly impact the catalytic activity. Certain catalysts may be more effective under specific pH conditions or in particular solvents due to their chemical properties or solubility.
Que >4 Explain the theory of Langmuir adsorption isotherm with its mathematical equations.
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• Langmuir considered that when the gas molecules strikes a solid surface, the surface adsorbs
some of this gas molecules and some are evaporated (or are desorbed rapidly).
• A dynamic equilibrium is eventually established between the two opposing process, adsorption
and desorption.
• Based on kinetic theory of gases, the assumptions are:
Conclusion:
• At low pressure, the amount of gas adsorbed (W) is directly proportional to pressure (P).
• At high pressure,the mass adsorbed reaches a constant value (A/B) when the adsorbent surface is completely covered with uni-molecular layer of gas
. • At this stage, adsorption is independent of pressure.
Applications of Adsorption
· In gas masks
· In catalysis
· In adsorption indicators
· In chromatographic analysis
· In softening of hard water
· In paint industry
· In removing moisture from air in the storage of delicate instruments
Que>4(OR) Discuss the classification of organic electronics materials. Write down their various applications.
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Classification : Organic electronics are classified in main three types
-Conductive organic materials
-Organic light emitting diode (OLED)
-Organic Field effect transistor (OFET)
(1.) Conductive organic materials
Conductive polymers are often typically intrinsically conductive or at least semiconductors. They sometimes show mechanical properties comparable to those of conventional organic polymers.
Both organic synthesis and advanced dispersion techniques can be used to tune the electrical properties of conductive polymers.
The most well-studied class of conductive polymers include polyacetylene, polypyrrole, polyaniline, and their copolymers.
Poly (p-phenylene vinylene) and its derivatives are used for electroluminescent semiconducting polymers. Poly(3-alkythiophenes) are also a typical material for use in solar cells and transistors.
(2 ) Organic light emitting diode (OLED)
An OLED (organic light-emitting diode) consists of a thin film of organic material that emits light under stimulation by an electric current. A typical OLED consists of an anode, a cathode, OLED organic material and a conductive layer.
OLED organic materials can be divided into two major families:
(i) Small-molecule-based OLED
Small molecule OLEDs (SM-OLEDs) include organometallic chelates,fluorescent and phosphorescent dyes, and conjugated dendrimers.Fluorescent dyes can be selected according to the desired range of emission wavelengths; compounds like perylene and rubrene are often used.
(ii) Polymer light-emitting diodes (PLEDs),
Similar to SM-OLED, emit light under an applied electric current. Polymer- based OLEDs are generally more efficient than SM-OLEDs requiring a comparatively lower amount of energy to produce the same luminescence. Common polymers used in PLEDs include derivatives of poly(p-phenylenevinylene) and polyfluorene. The emitted color can be tuned by substitution of different side chains onto the polymer backbone or modifying the stability of the polymer.
(3) Organic field-effect transistor (OFET)
It is a field-effect transistor using an organic semiconductor in its channel. OFETs can be prepared either by vacuum evaporation of small molecules, by solution-casting of polymers or small molecules onto a substrate.
These devices have been developed to realize low-cost, large-area electronic products and biodegradable electronics. OFETs have been fabricated with various device geometries.
The most commonly used device geometry is bottom gate with top drain and source electrodes, because this geometry is similar to the thin-film silicon transistor (TFT) using thermally grown SiO2 as gate dielectric. Organic polymers, such as poly(methyl-methacrylate) (PMMA), can also be used as
dielectric.
Applications of Organic Electronics
Television
Cell phone screens
Wrist watch
Foldable smart phones
Roll top touch screen laptop
Automobiles
OLED lenses
Que>5 Write a note on physical properties of the portland cement.
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Physical properties of Portland cement
Fineness: The fineness of cement means the particles size of cement. It affects the hydration process of cement. That means it affects the rate of strength gain of cement.
Soundness : It is the ability of a cement to maintain a stable volume after setting.Good soundness cement doesn’t shrink after hardening.
Consistency: Consistency means the required water to produce plastic cement paste for particular cement. Thus one can know the water-cement ratio for better workability of the mix.
Setting Time: As soon as the water is mixed with Portland cement, the hydration process starts and it begins to set. Cement has two setting time, initial-setting time and final-setting time. In construction, initial-setting time shouldn’t be too early and final-setting time shouldn’t be too late. Normally, initial-setting time is 30 to 45 minutes and final-setting time is below 10 hours.
Compressive Strength : Minimum compressive strength result for 3 days mortar cube should be 16 N/mm2 and for 7 days cube should be 22 N/mm2.
Heat of Hydration: The cement reacts as soon as the water is added. It is called hydration. During hydration, cement generates heat. This is the Heat of Hydration.
Specific Gravity : Specific Gravity of cement is necessary for calculating the mass for the desired volume of cement. The Specific Gravity of normal type of cement is 3.15
Que>6 Explain top down and bottom up approaches for the synthesis of nano materials
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Top-down vs. bottom-up
• Top-down methods
– begin with a pattern generated on a larger scale, then reduced to nanoscale.
– By nature, aren‟t cheap and quick to manufacture
– Slow and not suitable for large scale production.
• Bottom-up methods
– start with atoms or molecules and build up to nanostructures
– Fabrication is much less expensive
Que>6(OR)
0.25 g of CaCl2 was dissolved in dil. HCI and diluted to 250 mL. A 100 mL of this solution required 20 mL of EDTA solution for titration. 100 mL of a hard water sample required 30 mL of the same EDTA solution for titration. A 100 mL of the same water sample on boiling, filtering required 10 mL of EDTA. Calculate the total, permanent and temporary hardness.
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Que>7 What are the factors affecting to the rate of corrosion?
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The rate and extent of corrosion depends mainly on (a) the nature of the metal (b) the nature of the environment. Ø (a) Nature of the metal
Que>8 Discuss the reverse osmosis method for the softening of hard water.
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Que>8(OR)
Explain in detail the importance of Green synthesis with suitable examples.
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Green synthesis, also known as sustainable synthesis or eco-friendly synthesis, refers to the development of chemical processes and methods that minimize the use of hazardous substances and reduce the generation of waste. It aims to promote environmentally friendly practices in the synthesis of various compounds, ranging from small molecules to complex materials. The importance of green synthesis lies in its potential to address environmental concerns, minimize ecological impact, and contribute to sustainable development. Here are some key aspects and examples highlighting the significance of green synthesis:
1)Environmental Impact: Green synthesis minimizes the use of toxic reagents, solvents, and catalysts that can have adverse effects on the environment. It reduces the generation of hazardous waste, including byproducts and unwanted substances. By employing sustainable practices, green synthesis helps prevent pollution, minimize energy consumption, and conserve resources.
Example: Traditional methods of organic synthesis often rely on toxic solvents such as benzene or chloroform. Green synthesis approaches, on the other hand, emphasize the use of non-toxic or biodegradable solvents such as water, ethanol, or vegetable oils, reducing the environmental impact associated with solvent usage.
2)Health and Safety: Green synthesis promotes the use of safer and less hazardous chemicals, minimizing the risks to human health and safety for both researchers and end-users. By avoiding toxic reagents and intermediates, it reduces the exposure to harmful substances and the potential for accidents or adverse health effects.
Example: The synthesis of pharmaceutical compounds using green chemistry principles focuses on the use of non-toxic starting materials and environmentally benign reaction conditions. This approach ensures the production of safer drugs with reduced side effects and improved patient safety.
3)Resource Efficiency: Green synthesis aims to optimize the use of raw materials, energy, and catalysts. It promotes the development of efficient processes that minimize waste generation and maximize the utilization of available resources. This approach contributes to sustainable resource management and reduces the ecological footprint of chemical synthesis.
Example: Green synthesis methods often involve the use of catalysis, which enables the use of lower reaction temperatures, shorter reaction times, and reduced amounts of reactants. For instance, the use of heterogeneous catalysts in the synthesis of fine chemicals and intermediates allows for efficient reactions, high selectivity, and easy catalyst recovery for reusability.
4)Renewable Feedstocks: Green synthesis encourages the use of renewable feedstocks derived from sustainable sources, such as biomass, agricultural waste, or carbon dioxide. By utilizing renewable resources, it reduces dependence on fossil fuels, promotes a bio-based economy, and mitigates the environmental impact associated with the extraction and utilization of non-renewable resources.
Example: The production of biofuels, such as biodiesel or bioethanol, exemplifies green synthesis. These fuels are derived from renewable biomass sources, such as vegetable oils or lignocellulosic materials, and offer a sustainable alternative to fossil fuels, reducing greenhouse gas emissions and contributing to climate change mitigation.
5)Application in Various Sectors: Green synthesis has wide-ranging applications across different sectors, including pharmaceuticals, materials science, agrochemicals, and fine chemicals. It enables the development of sustainable manufacturing processes, greener products, and eco-friendly materials, fostering a more sustainable and environmentally conscious industry.
Example: Green synthesis approaches have been employed in the production of biodegradable polymers and materials, such as polylactic acid (PLA) or cellulose-based materials. These materials offer alternatives to conventional plastics and reduce environmental pollution by minimizing plastic waste accumulation and enhancing biodegradability.