Important Guess Questions For Chemistry

Important Guess Questions for Chemistry

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Afbaue's principle,Hund's Rule, Hydrogen bonding, coordinate bond, Galvanising, Electrode potential,electroplating, e-waste., Adhesive, Glass wool, Isoprene, Asbestos , Global Warming., Batteries.Daniel cell.

Aufbau Principle: This principle states that electrons fill atomic orbitals of the lowest available energy level before occupying higher-energy levels.

Hund’s Rule: In atomic physics and quantum chemistry, Hund’s rules refer to a set of rules formulated by German physicist Friedrich Hund around 1925, which are used to determine the term symbol that corresponds to the ground state of a multi-electron atom.

Hydrogen Bonding: Hydrogen bonding is the formation of hydrogen bonds between a hydrogen atom and a highly electronegative atom in a molecule. It is a special class of attractive intermolecular forces that arise due to the dipole-dipole interaction.

Coordinate Bond: A coordinate bond is a type of covalent bond where both shared electrons are donated by the same atom.

Galvanising: Galvanisation or galvanising is the process of applying a protective layer of zinc to steel or iron to prevent rust. The most common method is hot-dip galvanizing, in which the parts are immersed in a bath of molten hot zinc.

Electrode Potential: In electrochemistry, electrode potential is the voltage of a galvanic cell built from a standard reference electrode and another electrode to be characterized1.

Electroplating: Electroplating is a process for producing a metal coating on a solid substrate through the reduction of cations of that metal by means of a direct electric current.

E-Waste: Electronic waste (or e-waste) describes discarded electrical or electronic devices. It is also commonly known as waste electrical and electronic equipment (WEEE) or end-of-life (EOL) electronics23242526.

Adhesive: Adhesive, more commonly referred to as glue, is any one of multiple substances which, when applied to two surfaces, will bond or seal them and resist separation pressure27.

Glass Wool: Glass wool is an insulating material made from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties28293031.

1.Differentiate between isotope and isobars with suitable examples.

Ans

The below table gives a few differences between isotopes and isobars.

Isobars	Isotopes
Chemicals elements which have the same mass	Different atomic structure of the same element
The atomic masses are equal	The atomic masses are different
Often the physical properties are similar	Usually, physical properties are different
Atomic numbers are different	Atomic numbers are the same
Chemical elements are different	Same chemical elements having different  mass numbers
40S, 40Ar, 40Ca. 40Cl, and 40K	6O, 17O, and 18O

2.What are the main postulates of Bohr's atomic theory mention at least three limitations of Bohr's atomic theory   .

 

Bohr’s Atomic Theory:

1. Electrons move in circles around the center of an atom (nucleus).
2. Each circle path has a fixed energy level.
3. The energy levels are represented by numbers like 1, 2, 3, and so on. These numbers are also called quantum numbers.
4. The lowest energy level is 1, which is closest to the nucleus.
5. When an electron gains energy, it can jump to a higher energy level. When it loses energy, it can fall to a lower energy level.

Limitations of Bohr’s Theory:

1. Heisenberg Uncertainty Principle Violation: According to Bohr, we can know both the path (position) and speed (momentum) of an electron at the same time. But according to Heisenberg, this is impossible.
2. Inability to Explain Larger Atoms: Bohr’s theory works well for small atoms like hydrogen but doesn’t work well for larger atoms.
3. Failure to Explain Zeeman Effect: Bohr’s theory can’t explain why a spectral line splits into several parts when a magnetic field is applied.
4. Failure to Explain Stark Effect: Bohr’s theory can’t explain why a spectral line splits into fine lines when an electric field is applied.

3.Define valency. Differentiate between electrovalency and covalency.write down the  dot structure of methane, ammonia, ethylene and magnesium chloride.

Valency: Valency is like the “handshake ability” of an atom. It tells us how many bonds an atom can make with other atoms.

Electrovalency vs Covalency:

• Electrovalency: Think of it like a game of “give and take”. One atom gives away its electron(s) and the other takes it. This happens in ionic bonds.
• Covalency: This is more like “sharing is caring”. Atoms share their electrons to form bonds. This happens in covalent bonds.

Dot Structures:

• Methane (CH4): Imagine carbon in the center with four hands, each hand holding a hydrogen.
• Ammonia (NH3): Nitrogen is in the center with three hands, each hand holding a hydrogen. It also has a pair of electrons (like a little cloud) above it.
• Ethylene (C2H4): Two carbons are holding hands (double bond). Each carbon also holds hands with two hydrogens.
• Magnesium Chloride (MgCl2): Magnesium gives away its two electrons, one to each of the two chlorines.

4.Define electrolysis .Explain the electrolysis of copper sulphate.Define degree of ionization. What are the factors that affect the rate of ionization.

Electrolysis: Electrolysis is like a magic trick where we use electricity to break apart a compound into its basic elements.

Electrolysis of Copper Sulphate: Imagine you have a blue solution of copper sulphate. You put two rods (called electrodes) into the solution and connect them to a battery.

When you switch on the battery, electricity starts to flow. This electricity breaks the copper sulphate into copper and sulphate.

The copper gets attracted to one of the rods (the negative one), and you can see a layer of copper forming on that rod. The sulphate reacts with water in the solution and forms some gases.

Degree of Ionization: The degree of ionization is like the “strength” of an acid or base. It tells us how much an acid or base can break up into ions when it’s in a solution.

Factors Affecting Ionization:

1. Nature of electrolyte: Some electrolytes break up into ions more easily than others.
2. Nature of the solvent: Some solvents can help electrolytes break up into ions better than others.
3. Dilution: If you add more water to the solution, the electrolyte can break up into ions more easily.
4. Temperature: If you heat up the solution, the electrolyte can break up into ions more easily.
5. Presence of other solutes: If there are other things dissolved in the solution, they can affect how easily the electrolyte breaks up into ions.

5.What are the main postulates of arrhenius theory of dissociation .Differentiate between strong electrolyte and weak electrolyte with suitable examples.

 

Arrhenius Theory of Dissociation: This theory is like saying when you dissolve some stuff (like salt) in water, they break up into tiny charged particles.

Electrolysis of Copper Sulphate: Imagine you have a blue liquid which is copper sulphate. You put two rods in the liquid and connect them to a battery. When you switch on the battery, the copper sulphate breaks up into copper and sulphate. The copper sticks to one rod and the sulphate makes some gases.

Strong Electrolyte vs Weak Electrolyte:

• Strong Electrolyte: These are like salt. When you dissolve them in water, they break up completely into tiny charged particles.
• Weak Electrolyte: These are like vinegar. When you dissolve them in water, only a little bit of them break up into tiny charged particles.

 6.What is electrochemical corrosion. Explain the mechanism of rusting of iron.

Electrochemical Corrosion: This is when a metal breaks down because it reacts with things around it. It’s like when a bike left in the rain starts to rust.

Rusting of Iron: Rusting is like a metal’s version of a bad day. It happens when iron meets water and oxygen (like in humid air). The iron reacts with water and oxygen to form rust, which is a kind of iron oxide (a fancy term for rust). This rust sticks to the iron, making it flaky and weak3.

7.Define corrosion. what are the factors that affect the rate of corrosion? suggest some preventive measures to counter the rate of corrosion.

Corrosion: Corrosion is like a metal’s “bad day”. It’s when a metal breaks down because it reacts with things around it, like air and water.

Factors Affecting Corrosion:

Wetness: Metals corrode faster in wet places3.

Temperature: Metals corrode faster when it’s hot3.

Air: Certain gases in the air can make metals corrode faster3.

Impurities: Things like salt can make metals corrode faster3.

Type of Metal: Some metals corrode faster than others3.

Preventive Measures:

Painting: Painting metals can protect them from air and water4.

Oiling and Greasing: This also forms a protective layer on the metal surface4.

Galvanisation: This is a process where a protective layer of zinc is made on iron and steel objects4.

Alloying: This is when we mix a metal with other elements to make it stronger

8. Explain air pollution due to internal combustion engine and suggest some measures to control it.

Air Pollution from Engines: Engines in cars and trucks burn fuel. When fuel burns, it creates smoke and gases. These gases are let out through the exhaust pipe of the vehicle1. The gases include carbon dioxide, methane, and nitrous oxide1. These gases can cause problems like global warming1.

How to Control It: There are a few ways to reduce the pollution from engines21: 

New Combustion Systems: These are new ways to burn fuel that create less pollution1.

Turbocharging: This is a way to get more power from the engine without burning more fuel1.

Better Engine Design: Making changes to the engine can help it burn fuel more cleanly1.

Exhaust Gas Recirculation (EGR): This is a way to recycle some of the exhaust gases back into the engine. It helps to reduce the amount of harmful gases that are released.

NOx After Treatments: These are special treatments that can reduce the amount of nitrous oxide (a harmful gas) that is released1.

9.State faraday's law of electrolysis. Calculating amount of charge required if 2A of current is passing through an electrolytic solution of ZnSO4 and AgNO3  and deposited mass is given 3.5 gm and 4.2 gm rps.(  For Example only)

Faraday’s Law of Electrolysis: Faraday’s law says that the amount of a substance that appears at an electrode during electrolysis is directly related to the amount of electricity that flows through the solution.

Calculating Charge: If you have a current (like water flow, but with electricity) of 2A (A stands for Ampere, which is a measure of current) flowing for a certain time, the total charge (Q) can be calculated by multiplying the current (I) by the time (t) in seconds.

For example, if you have 2A of current and it flows for 1 hour (which is 3600 seconds), the total charge would be 2A * 3600s = 7200 Coulombs.

The amount of substance that gets deposited (like the 3.5 gm and 4.2 gm you mentioned) depends on the total charge and the type of substance34. Each substance has a specific amount of charge needed to deposit 1 gram of it.

10. Define water pollution. Discuss the role of D. O, C.O. D, and B. O. D in forming water quality Index.

Water Pollution: Water pollution is when harmful stuff (like chemicals or waste) gets into water bodies (like rivers, lakes, or oceans) and messes up the water so much that it’s not good for use anymore.

D.O. (Dissolved Oxygen): This is the amount of oxygen that is mixed in the water. Fish and other water creatures need this oxygen to live. If there’s not enough D.O., these creatures can’t survive.

C.O.D. (Chemical Oxygen Demand): This is a measure of how much oxygen would be needed to break down all the organic material in the water6. A high C.O.D. means there’s a lot of organic material, which could be a sign of pollution.

B.O.D. (Biochemical Oxygen Demand): This is similar to C.O.D., but it measures how much oxygen would be used by bacteria to break down the organic material5. A high B.O.D. means there’s a lot of organic material for bacteria to eat, which could use up the oxygen in the water and make it hard for other creatures to live.

These three measures (D.O., C.O.D., and B.O.D.) are used together to figure out the quality of the water. If the D.O. is low or the C.O.D. and B.O.D. are high, it could mean the water is polluted.

11. Define biomedical waste. Discuss it's effect and control measures.

Biomedical Waste: Biomedical waste is like the trash that comes out of places like hospitals or clinics. This trash can have germs or chemicals that can make people sick.

Effects of Biomedical Waste: If biomedical waste is not handled properly, it can cause a lot of problems. It can spread diseases like HIV, hepatitis, and tuberculosis6. It can also cause infections and lung problems6. Plus, it can pollute the environment, like the soil, water, and air.

Control Measures: There are several ways to manage biomedical waste properly:

Understanding the Laws: Every place has laws about how to handle biomedical waste. It’s important to know and follow these laws.

Waste Management Plan: This is a plan that tells people how to handle the waste properly.

Using Reusable Products if Possible: Some things can be cleaned and used again, which reduces the amount of waste.

Proper Segregation: Different types of waste need to be kept separate from each other.

12. What do you mean by valcanisation of rubber? Diffentiate b/w natural and synthetic rubber.Write down the composition and application of Buna-S, Buna-N and Neoprene.

Vulcanisation of Rubber: Vulcanisation is a process that makes rubber stronger. It’s done by heating rubber with sulfur. This makes the rubber more resistant to wear and tear and allows it to keep its shape better when stretched.

Natural vs Synthetic Rubber: Natural rubber comes from a plant, while synthetic rubber is made by people456. Natural rubber is strong, flexible, and heat-resistant4. Synthetic rubber is better at resisting temperature changes, ageing, and wear and tear. It’s also usually cheaper to make.

Buna-S: Buna-S, also known as Styrene-Butadiene Rubber (SBR), is made from butadiene and styren. It’s used for making things like tyres, floor tiles, footwear components, and cable insulation.

Buna-N: Buna-N, also known as Nitrile rubber or NBR, is made from acrylonitrile and butadiene. It’s used in the automotive and aeronautical industry to make fuel and oil handling hoses, seals, and grommets.

Neoprene: Neoprene, also known as polychloroprene, is a synthetic rubber made from chloroprene. It’s used in a wide variety of applications, such as laptop sleeves, orthopaedic braces, electrical insulation, medical gloves, and automotive fan belts.

13.Define thermosetting polymers with example. Discuss their properties and applications.

Thermosetting Polymers: Thermosetting polymers, also known as thermosets, are like dough that’s been baked into bread. They start off soft and moldable, but once they’re heated, they harden and can’t be softened again. An example of a thermosetting polymer is Bakelite.

Properties of Thermosetting Polymers: Thermosetting polymers have some special properties45:

Heat Resistant: They don’t melt when they’re heated45.

Hard and Brittle: They’re hard and can break if you try to bend them45.

Cannot Be Reshaped: Once they’re formed, they can’t be reshaped45.

Applications of Thermosetting Polymers: Thermosetting polymers are used in many different ways467:

 

Making Permanent Parts: They’re used to make parts that need to be strong and last a long time4.

Electrical Goods: They’re used to make things like panels and insulators4.

Construction Equipment: They’re used to make panels for construction equipment4.

Heat Shields: Because they’re heat resistant, they’re used to make heat shields4.

Automobiles: They’re used to make parts like brake pistons in cars4.

14. Define paints and it's composition with example . What are the characteristics of a good paint?

Paints: Paints are like a special kind of liquid that we use to color things. When you put paint on something, it dries and leaves a colored layer.

Composition of Paints: Paints are made of four main things:

Pigments: These give the paint its color.

Binders or Resins: These help the paint stick to the surface.

Solvents: These keep the paint liquid until it’s applied.

Additives: These give the paint special properties, like being able to resist weathering, chemicals, and abrasion1234.

Characteristics of a Good Paint: A good paint has several characteristics:

Good Hiding Power: It should be able to cover the surface well.

Color: The color should not fade quickly.

Resistance: It should be able to resist the weather and other conditions.

Easy Application: It should be easy to apply evenly.

Economical in Cost: It should not be too expensive.

15.  What are resins.?Discuss synthesis and applications of phenol formaldehyde resin.

Resins: Resins are like a special kind of sticky stuff that comes from plants or can be made by people. They’re usually a mix of organic compounds. They can be solid or really thick and sticky. They’re used in things like varnishes, printing inks, plastics, and medicines.

Phenol Formaldehyde Resin: Phenol formaldehyde resin is a type of resin that’s made by reacting phenol (a type of alcohol that comes from benzene) with formaldehyde (a gas that comes from methane)45. There are two main ways to make it:

One way is to react phenol and formaldehyde directly to make a thermosetting network polymer45.

The other way is to restrict the formaldehyde to make a prepolymer known as novolac, which can be moulded and then cured with the addition of more formaldehyde and heat.

Applications of Phenol Formaldehyde Resin: Phenol formaldehyde resins have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives56. They were at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fiberglass cloth.

16. What are lubricants? Discuss the types and working mechanism of lubricants.

Lubricants: Lubricants are like a special kind of liquid or solid that we use to make things move more smoothly. They help reduce the friction between surfaces that are in contact with each other, which makes the surfaces move more easily and reduces the heat that’s produced when the surfaces move.

Types of Lubricants: There are four main types of lubricants:

Oil: This is the most common type of lubricant. It’s used in many machines and engines.

Grease: This is a semi-solid lubricant that’s often used in situations where liquid oil would not stay in place.

Penetrating Lubricants: These are special lubricants that can get into small spaces between surfaces.

Dry Lubricants: These are solid materials like graphite or molybdenum disulphide that can be used in situations where oil or grease would not be suitable.

Working Mechanism of Lubricants: When a lubricant is applied between two surfaces, it forms a thin film that separates the surfaces and prevents direct metal-to-metal contact. This reduces the friction between the surfaces, which makes the surfaces move more easily and reduces the heat that’s produced when the surfaces move.