Chemistry
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Question paper 1
SECTION- A
Q. 1 Fill in the blanks.
a. Dimensional formula of force is ________________
Answer:
[MLT-2]
b. Units of molarity are____________-
Answer:
Moles/litre
c. M shell has ________ sub shells.
Answer:
Three sub shells
d. Neutron was discovered by__________
Answer:
James Chadwick
e. Chemical name of permutit is _________
Answer:
Sodium Aluminium Silicate (Na2Al2Si2O8.xH2O) or Zealot.
f. A base is a proton_____________
Answer:
Acceptor
g. Anions are_________charged ions.
Answer:
Negative
h. The functional group of amide is____________
Answer:
RCONH2
State True or False.
i. Ions are neutral particles.
Answer:
False
j. There are 18 vertical columns in the periodic table.
Answer:
True
k. No two electrons can have same set of four quantum numbers .
Answer:
True
l. Soft water does not give lather with soap.
Answer:
False
m. Degree of ionisation decreases with dilution .
Answer:
False
n. Oxidation and reduction go hand in hand .
Answer:
True
o. Alkenes are unsaturated hydrocarbons.
Answer:
True
SECTION: B
Q2 Attempt any ten questions.
a. Give three limitations of a chemical equation
Answer:
Limitations of chemical equation:-
1) The physical state of reactants and products.
2) The concentration of reactants and products.
3) The condition of temperature, pressure, catalyst, etc. which are needed for a reaction.
4) The state of reaction whether slow or fast.
5) Time taken by the reaction for completion.b. Calculate the actual mass of one atom of carbon.
Answer:
We know the relative atomic mass of 12 C is 124.
So, mass of 1mol C = 12 g
Mass of 6.022 x 1023C atoms=12 g
Actual mass of 1C atom= 12/6.022 x 1023 (Avogadro number) = 1.99 x 10-23 g
c. Define the terms Electron, Proton and Neutron.
Answer:
Electron:- These are tiny particles which are negatively charged. Electrons revolve in orbital around the nucleus in which protons and neutrons are present. The electrons are negatively charged particles and make the atom neutral because there is equal number of positively charged protons are present in the nucleus. Charge on electron is -1. Mass of electron is 9.11 x 10-31 kg. And represented by e-.
Proton:- The proton is, in effect, the index particle of any atom. It is the number of protons in an atom that determines the identity of the elements in an atom belongs to. In other words, if two atoms have a different number of protons, they are not the same element. Atoms only exist with only a proton in their nucleus, as is the case with the hydrogen atoms in nucleus protons and nucleus are present. Charge on the proton is +1 and represented by ‘p’. The mass of proton is 1.00728amu (atomic mass unit).
Neutron:- neutron are similar in size of protons, with an amu of 1.00867 and also inhibit the nucleus of atoms. The neutron is a neutral particle. Therefore, the charge on nucleus is zero and represented by n0.
d. Define covalent bonding with examples.
Answer:
Covalent bonding is chemical bonding process in which pairs of electrons are shared between two atoms. The force of attraction or repulsion between two atoms, when they share electron pair or bonding pairs is called covalent bonding. It occurs between non-metal elements when pairs of electrons are shared by atoms
Example:- simple example is CH4. The carbon atom has 4 electrons in the outer most orbital and for completing its octet and attain nearest noble configuration carbon atom wants 4 electrons. Hence, it makes 4 covalent bond with hydrogen which shares its 4 electrons and makes 4 covalent bonds.
The carbon dioxide is also example of covalent bonding (CO2). Here two oxygen gives 4 electrons (one oxygen gives 2 electrons) to the carbon atom.
O : : C : : O
e. What are the advantages of long form of periodic table?
Answer:
(1) This clarification is based on the atomic number which is more fundamental property of the elements.
(2) It is easy to remember and reproduce.
(3) The systematic grouping of elements into four blocks s, p, d & f has made the study of the element more simple.
(4) The lanthanides and actinides which have properties different from other groups are placed separately at the bottom of the periodic table.f. Differentiate between temporary and permanent hardness of water.
Answer:
S.NO.
TEMPORARY HARDNESS
PERMANENT HARDNESS
1.
It is due to the presence of bicarbonates of calcium and magnesium.
It is due to the presence of chlorides of sulphates of calcium and magnesium.
2.
It can be remaining by boiling point.
It cannot be remaining by boiling point.
3.
Hardness removal is cheap.
Hardness removal is expensive.
g. Explain scale and sludge formation.
Answer:
In boilers, water evaporates continuously and the concentration of the dissolved salts increases progressively. When their concentrations reach saturation point, they are thrown out of water in the form of precipitates on the inner walls of the boiler. If the precipitation takes place in the form of shiny precipitates, it is called “sludge”. On the other hand, if the precipitated matter forms a bond adhering crust/ coating on the inner walls of the boiler, it is called “scale”.
h. What is Boyle’s law, Avogadro’s law and Absolute zero?
Answer:
Boyle’s law:- In 1662 Robert Boyle’s law was published according to this law. “The absolute pressure and volume of given mass confined gas are inversely proportional, provided the temperature remains unchanged within a closed system.”
Mathematically, P1/V1 = P2/V2 at constant temperature (T).
Avogadro’s law:- Avogadro’s law state that under condition of constant pressure & temperature. There is a direct relationship between the number of moles and volume of a gas. This law is applicable to ideal gases, while real gases show a slight deviation from it.
The modern definition of this law is that for particular mass of an ideal gas. The amount (number of moles) and volume of the gas are directly proportional , provided the temperature and pressure conditions are constant.
Mathematically, V/n = k.Absolute Zero:- It is defined as the point where no more heat can be removed from a system, according to the absolute or thermodynamic temperature scale. This corresponds to 0 Kelvin or -273.15C. at this temperature at which a thermodynamic system has the lowest energy.
i. What are strong and weak electrolytes?
Answer:
Electrolytes are chemicals that break into ions in water. Aqueous solution containing electrolytes conduct electricity.
Strong Electrolyte:- It includes strong acids, strong base and salts. These chemicals completely dissociate into ions in aqueous solution.
Molecular example:- HCl, HBr, NaOH, NaCl, etc.
Weak Electrolytes:- It only partially breaks into waters. Weak electrolytes include weak acids, weak base & a variety of other compounds. Most compounds that contain nitrogen are weak electrolytes.
For example:- HF, CH3COOH, NH3, H2O (weakly dissociates in itself).j. Calculate the pH value of 0.001 M HCL.
Answer:
HCl is strong electrolyte & completely dissociate into H+ and Cl-.
pH= -log(H+)
so, 0.01M of HCl
H+ ions in water =0.01 moles.
pH= -log(0.01)
[log(0.01)=2]
pH=-(-2)
hence, pH=2
k. Explain Faraday’s second law of electrolysis.
Answer:
Faraday’s Second Law:- This law states that “the mass of a substance deposited or liberated at any electrode on passing a certain amount of charge is directly proportional to its equivalent weight of the substance.
That is, W ∞ E
W is mass of substance in grams.
E is chemical equivalent i.e. weight in grams per equivalent.l. What are primary and secondary cell?
Answer:
Primary Cells:- The cells that can be used only once and disposed after the usage.
Primary cells function with chemical reactions. The discharge rate is lower than that of secondary cells. The initial cost of these cells is lesser than that of secondary cells.
Secondary Cells:- The cells that can be recharged after usage(after discharging), and it is possible to use them several times.
Secondary cells have a quick discharge rate & need to be recharged again and again.
These cells initial cost is more than primary cells. All mobile phones use these kinds of cells.m. What is the formula of
(a) Acetic acid (b) Acetaldehyde (c) Acetone
Answer:
SECTION C
Attempt any three questions.
Q3. (a) Give the main features of Bohr’s atomic model.
(b) Balance the following equation by hit and trial method.
Fe + H2O Fe3O4 + H
Answer:
(a) Main features of Bohr’s atomic model.
(1) Electrons revolve in stable orbits around the nucleus. There is no emission of radiant energy. Energy orbit has definite energy called energy shell or energy level.
(2) An energy level or orbit has been designated as the K,L,M,N shell. An electron is said to be in its ground state when it is in the lowest Energy level.
(3) While jumping from one orbit or energy level to another, the electron either emits or absorb energy. When the electron jumps from energy shell with higher energy to an energy shell of lower energy, the electron emits energy. But when the electron jumps from the lower energy level to the higher energy level, the electron absorbs energy.
(4) The energy that is absorbed or emitted by the electron is equal to the difference between the energies of the two energy level (E1 &E2) which is later determined by Plank’s equation
(b) 3Fe + 4H2O → Fe3O4+ 8H+
Q4. (a) Name the four quantum numbers and explain the significance of each quantum Numbers
(b) Explain Ionic bond with examples.
Answer:
(a) Quantum numbers describe an address or full description of the electrons.
1. Principal quantum number (n):- It defines the main shell to which on electrons belongs. The value of n=1,2,3,4.......
2. Azimuthal quantum number (l):- It tells us the number of sub shells present in the main shell and the orbital to which an electron belongs. Its value to 0 to n-1.
3. Magnetic quantum number(m):- It informs the level of degeneracy of the orbital. Its value is equal to -1,0,+1.
4. Spin quantum numbers (ms):- It tells us that whether the electron is an orbital is spinning in upward direction or downward direction. It has two values +1/2 for upward spin and -1/2 for downward spin.(b) Ionic bond is a type of chemical bond that has formed as a result of the complete transfer of valence electrons from one molecule to another metals will transfer their valence electrons to non-metals forming a positively charged ions. The atoms that accept the electrons become negatively charged. The two opposite charge will be attached towards each other and form an ionic bonds and are therefore ionic compounds.
For example:-
Nacl (Sodium Chloride- table salt)
CaCl2 (Calcium Chloride
NaOH(Sodium Hydroxide- soap)
Fe2O3 (Iron Oxide- rust)Q5. (a) A sample of hard water is found to contain 285mg of MgCL2/L. What will be its hardness in ppm? (Mg =24, CL= 35.5, O=16, C=12 Ca = 40 )
(b) What are the various factors affecting the degree of ionisation?
Answer:
(a) Hardness =
Hardness =
= 300ppm (ppm= 101/6)(b) 1. At normal dilution, value of
is nearly 1 for strong electrolytes, while it is very less than 1 for weak electrolytes.2. Higher the dielectric constant of a solvent more is its ionising power.
3. α x 1/ concentration of solution x 1/ weight of solution x dilution of solution α x amount of solvent.
4. Degree of ionisation of an electrolyte in solution increases with rise in temperature.
5. Presence of common ion: the degree of ionisation of an electrolyte decreases in the presence of strong electrolytes having a common ion.
Q6. (a) How will you remove hardness of water by Permutit process?
(b) Explain oxidation and reduction with examples
(c) Explain pH scale
Answer:
(a) Permutit is a man-made zealot. The chemical formula zealot is Na2AlO3.nSiO2.xH2O.
Zealot is made up of micro-porous minerals which have the capacity of exchanging ions. Hence zealot is used to remove the hardness of water because the zealot contains Sodium(Na) and Aluminium(Al) which makes the water soft in nature.
Ca and Mg is mainly responsible for the hardness of water. A permutit is packed into the reservoir from which the hard water is allowed to pass. When the water passes through permutits; exchange of ions take place i.e. ca and Mg is replaced by Na and Al.
(b) Oxidation is process in which there is addition of oxygen or removal of hydrogen or removal of hydrogen or removal of electrons from that compound.
For example:- O [O] O
R-C?-H ---------> R-C?-OH (Addition of oxygen)
[-2H] O
R-CH2OH--------------> R-C?-H (Removal of hydrogen)
[Ce4+]
R-CH2-O- -------------> R-CH2-O (Removal of electrons)
Reduction is the process in which removal of oxygen or addition of hydrogen or addition of electron from the compound.
H2/Catalyst
For example:- R-CH=CH2 ---------------------------> R-CH2-CH3
(c) The pH scale measures how acidic or basic a substance is. It ranges from 0 – 14. If pH is lower than 7 it indicates the solution is an acid and if it is above 7 then it is a base or alkaline. If pH is 7 then it is neutral. Strong acids have lower pH than the weak acids. Strong bases have higher pH than the weak bases. A pH is measured by dipping litmus into the solution such as water or other substances.
Q7. (a) Differentiate between saturated and unsaturated hydrocarbons by giving examples.
(b) Give the general formula of alkane, alkene and alkyne.
(c) Explain the term catenation.
Answer:
(a)
S.No
Saturated Hydrocarbons
Unsaturated Hydrocarbons
1.
They have single covalent bonds
They have multiple double or triple bonds
2.
They have less amount of carbon & more hydrogen
They have less amount of hydrogen & more carbon
3.
These are less reactive.
These are more reactive.
4.
Burning in air results in blue non sooty flame.
Burning in air results in yellow sooty flame.
5.
Eg. CH3-CH3, CH3-CH2-CH3
Eg. CH2 =CH2, R-CH=CH2, CH=CH
(b)
Alkane CnH2n+2 , Alkene CnH2n , Alkyne CnH2n-2
N = 1,2,3,____
(c) Catenation is the binding of an element to itself through covalent bond to form chain or ring molecules. Carbon is the most common element that exhibits catenation. It can form long hydrocarbon chains and ring like benzene.
-[-CH2-CH2-CH2-]-n &
Question paper 2
SECTION – A
Q1 (a) Fill in the blanks.
i. Calcination is heating the ore in the______ of air.
Answer:
limited supply
ii. The purest form of iron is ______.
Answer:
Wrought
iii. The metal acting as ______ is always get corroded.
Answer:
iron
iv. Producer gas is a mixture of ______.
Answer:
CO2 +H2
v. A good fuel should possess ______ ignition temperature.
Answer:
moderate
vi. The unit of viscosity is ______.
Answer:
catalyst
vii. Lime acts as a ______ in silica bricks.
Answer:
viii. Enamel is pigmented ______.
Answer:
Vinyl chloride
ix. The monomer of polyvinylchloride is ______.
Answer:
m2s-1
x. A pigment imparts ______ to paint.
Answer:
coloring
(b) Fill in the blanks.
i. Combustion of a fuel is an exothermic process.
Answer:
True
ii. Mineral oils are good in oiliness.
Answer:
True
iii. Nylon -66 is obtained by addition polymerization reaction.
Answer:
False
iv. Corrosion involves oxidation process.
Answer:
True
v. A forestation causes air pollution
Answer:
False
SECTION – B
Q2. Attempt any ten questions.
a. Explain Froth flotation process for the concentration of sulphide ores.
Answer:
This method is used for concentration of sulphide ores of copper, zinc and lead. In this method, powdered ore is put in a tank full of water. And then, some Pine oil is added to it. In the tank, the particles of sulphide ores wetted by pine oil whereas the gangue (impurities like rock particles, sand, etc.) particles are wetted by water. Then air is passed through this mixture. This results in the agitation of water in tank. Which cause the sulphide ore particles to stick with the oil and rise to the surface in the form of the froth? The gangue particle being heavier remains behind at the bottom of water tank. The froth is separated and concentrated sulphide ore is obtained from it.
b. What is the difference between cast iron, wrought iron and steel?
Answer:
Wrought Iron
Cast Iron
Steel
COMPOSITION
Purest form contains up to 0.25%C
Crude form containing 2.4 C
Midway
MELTING PT.
1500 C
1200 C
1300-1400 C
HARDNESS
Cannot be hardened or tempered
Hard, hardened by heating & sudden cooling
Can be hardened and tempered
STREGNTH
Compressive strength is 2.0 Tonnes/sq cm
Compressive strength 6.3-7.1 Tonnes/sq cm
Compressive strength is 4.75-5.2 tonnes/sq cm
c. What is the cause of corrosion?
Answer:
Corrosion is an electrochemical process that actually causes some metal to be broken down. It commonly occurs to anode metals when they come into contact with an electrolyte (such as water), oxygen & a cathode(a substance which accepts electrons). A metal’s electrons will flow through the electrolyte and into the cathode, causing the item to wear away. If you add salt to the water the process of corrosion in your item will speed up substantially.
d. Distinguish between octane number and cetane number.
Answer:
S.no.
Octane number
Cetane numbers
1
It measures the performance of fuel.
It measures the delay of the ignition of a fuel.
2
Important for predicting the knocking of an engine.
Important for predicting the ignition of an engine.
3
It is given for gasoline.
It is given for diesel.
4
Octane rating is done considering the octane number of isooctane as 100.
Cetone rating is done considering the ignition of cetone.
e. Write a short note on natural gas.
Answer:
Natural gas, colorless highly flammable gaseous hydrocarbon consisting primarily of methane and ethane. It is a type of petroleum that commonly occurs in association with crude oil and fossil fuel. Natural gas is used for electricity generation, heating and cooking & as a fuel for certain vehicles. It is important as a chemical feedstock in the manufacture of plastic. These gases are often found dissolved in oil at the high pressures existing in reservoir. It often considered to be the gaseous phase of the crude oil & usually contains some light liquid such as propane and butane.
f. Define viscosity. What is the effect of temperature on viscosity?
Answer:
Viscosity:- It is quantity that shows resistance to path of fluids flow. Fluid’s resist the relative motion of immersed objects through them as well as to the motion of layers with various velocities within them. It is represented by ?. Viscosity of liquids decreases with increasing temperature. Increase in temperature reduces the cohesive forces between the molecules of liquid and hence the viscosity decrease with temperature.
g. Name the various constituents of paint. Explain the functions of a drying oil.
Answer:
Pigments:- Prime pigments to imparts color & opacity
Winder:- A polymer often referred to as resin, forming a motion to hold the pigment in place
Extender:- Larger pigment particles added to improve adhesion.
Solvent:- Either an organic solvent or water is used to reduce the viscosity of the paint for better application.
Additives:- used to modify the properties of the liquid paint or dry film.
Function of Drying oil:- The most important and unique function of oil paints is the thin coating of oil on each particle of pigment. The coating consists of a drying oil such as linseed or poppy oil. The oil dries through oxidation; a chemical reaction between the oxygen in the air and the oil, and through evaporation.h. What is a glass? What is the composition of glass?
Answer:
Glass is an amorphous solid. Glass does not have any crystalline structure. They usually are hard and brittle solids. Glass is the name given to any amorphous solid that displays a “glass transition” near its melting point. This is related to the glass transition temperature, which is the temperature where an amorphous solid becomes soft near its melting point or a liquid becomes brittle near its freezing point.
Composition of glass:-
Silicon dioxide (SiO2)
Limestone Or calcium carbonate (CaCO3)
Sodium carbonate (Na2CO3)i. State and explain Pilling- Bedworth rule.
Answer:
The Pilling-Bedworth ratio (P-B ratio), in terms of metal corrosion, is the ratio of elementary cell volume of metal oxide to the elementary cell. Volume of the equivalent metal where the oxide has been created. By using the P-B ratio, it can be determined if it is possible for the metal to undergo passivation in the presence of dry air building a protective oxide film. The metal oxide P-B ratio can be best described as the ratio of the metal oxide volume produced by the oxygen and metal reaction to the consumed value of metal. This can be further defined in the equation:
RPB = Voxide / Vmetal = (Moxide x Pmetal) / n x (Mmetal x Poxide)RPB = Ratio(Pilling-Bedworth)
M = Molecular or atomic mass
n = Metal atom per one oxide molecule
v = The molar value
P = The density.j. Differentiate between thermoplastics and thermosetting plastics.
Answer:
S. No
Thermoplastics
Thermosetting plastics
1
It can be synthesised by the process called addition polymerisation.
It can be synthesised by condensation polymerisation.
2
These have secondary bonds between molecular chains.
These have primary bonds between molecular chains and held together by strong cross links.
3
These have low melting points.
These have high melting points.
4
They have low tensile strength.
They have high tensile strength.
5
They are low in molecular weight
They are high in molecular weight
k. How is Nylon-66 synthesized from its monomers? Write its uses.
Answer:
Nylon-66 is made or synthesised by acid and hexamethylene diamine. It is a condensation reaction. To make nylon 66 one doesn’t need a catalyst, but acids to catalyse the reaction, and one of the monomers is itself an acid.
REACTION
Uses of Nylon-66:-
1. It is waterproof in nature so it is used in swimwear.
2. It is light material so it is also used in parachutes.
3. It is also used in manufacturing airbags, carpets, ropes, etc.
4. It is also used to make machine parts.l. What are the characteristics of a good refractory material?
Answer:
Characteristics of a good refractory material
(1) Be infusible at the temperature to which it is liable to be exposed.
(2) Chemically inert towards corrosive action of gases, metallic liquid & slag.
(3) Resist the abrasive action of gases, flames, etc.
(4) Be able to withstand the overlying load of structures at the operating temperature
(5) No loss in size.
(6) Expand and contract uniformly, with temperature rise and fall respectively.m. What are primary and secondary pollutants? Give two examples of each
Answer:
Primary pollutants:- It is an air pollutant emitted directly from sources.
For example: oxides of sulphur, oxides of nitrogen, oxides of carbon, etc.
Secondary pollutants:- It is not directly emitted as such but forms when other pollutants (primary) react in the atmosphere.
For example: ground-level ozone, smog and persistent organic pollutants (pops), etc.Section C
Attempt any 3 questions.
Q3. Name the important ores of copper. Describe the extraction of copper from its
main ore.Answer:
The main ores of copper ore chalcopyrite(CuFeS2), chalcocite(Cu2S), bornita(2Cu2S.CuSFeS), diganite(Cu9S5), cuprite(Cu2O).
Chalcopyrite(CuFeS2) is the main ore of copper which is also known as copper pyrites. It is converted to copper by different method from silicates, carbonate or sulphate ores. The ores typically contain low percentage of copper and have to be concentrated before refining (e.g. via froth flotation).
The Process:- the concentrated ore is heating strongly with silicon dioxide and air or oxygen in a furnace or series of furnaces.
-> The copper (II) ions in the chalcopyrite are reduced further to copper (I) sulphide which is reduced further to copper metal in the final stage.
-> The iron in the chalcopyrite ends up converted into an iron (II) silicate slag which is removed.
-> Most of the sulphur of the chalcopyrite turns into sulphur dioxide gas. This is used to make sulphur dioxide gas. This is used to make sulphuric acid via the contact process.
An overall equation for this series of steps is:-
2CuFeS2+2SiO2+4O2--------------------> Cu2S+ 2FeSiO3+3SO2The copper(I) sulphide produced is converted to copper with a final blast of air.
Cu2S+O2--------------------> 2Cu +SO2Q4 (a) What are the theories of corrosion? Describe briefly the acid theory.
(b) What are the advantages of gaseous fuels over the solid fuels?
(c) What are anti-knock compounds? Give two examples.Answer:
(a) The process of slowly eating away of the metal due to attack of the moisture & atmospheric gases on the surface of the metal resulting into formation of compound such as oxides, sulphides, carbonates, sulphates is called corrosion.
The phenomenon of corrosion can be described as
At anode:
Fe(s) undergoes oxidation to release electrons
Fe(s) → Fe2+(aq) + 2e-
At cathode:
O2(g) + 4H+ + 4e- → 2H2O(e)
Electrons released at anode move to another metal & reduce oxygen in the presence of H+. It is available from H2CO3 formed from the dissolution of CO2 from air into water H+ in water may be available also through dissolution of other acidic oxides from the atmosphere.
Net reaction:
Fe(s) +2H+(aq)+1/2 O2(g) - → Fe2+(aq) + H2O(g)
Fe2+ again gets oxidised to form rust.
Fe(s) +2H+(aq)+1/2 O2(g) - → Fe2O3(s) + 4H+
(Rust)
Acid theory of corrosion:- Acid theory suggests that corrosion of metal(iron) is due to the presence of acid around it. According to this theory, iron is corroded by atmospheric CO2, moisture and oxygen. the corrosion products are the mixture of Fe(HCO3)2, Fe(OH)Co3 & Fe(OH)3. The chemical reaction suggested are given below:
Fe +2CO2+H2O+1/2O2 ----------------------> Fe(HCO3)2
2Fe(HCO3)2 +H2O + 1/2O2 -------------------> 2Fe(OH)CO3+ 2CO2+ 2H2O
2Fe(OH)CO3+ 2H2O---------------> 2Fe(OH)3+2CO2
(b) Advantages:-
(1) Gaseous fuel is easier to handle than solid fuels.
(2) Gaseous fuels can be transported easily through pipelines where as solid fuels cannot be transported in this way.
(3) Liquid and gaseous fuels do not leave any residue after burning.
(4) Gaseous fuel has higher calorific value than the solid fuel.
(5) Gaseous fuel produce little or no smoke, whereas most of the solid fuels burns with smoke.(c) Anti-knocking compound is that compound which is added to gasoline to eliminate knocking of engine. E.g. Pb(C2H5)4 is good antiknock. Alcohol, ferrocene, toluene, etc. are also anti-knocking agent.
Q5 (a) What are super conductors? What are their types?
(b) What is a varnish? What are the characteristics of a good varnish?
(c) Explain the mechanism of thin film lubrication.Answer:
(a) A superconductor is an element or metallic which when cooled below a certain threshold temperature, the material dramatically closes all electrical resistance. In principle, superconductor can allow electrical current to flow with any energy loss. The type of current is called a super current.
The threshold temperature below which a material transition into a super conductor state is designated as to which stands for critical temperature. Not all materials turn into super conductors & the materials that do each have their own value of Tc.Types of super conductors:-
Type I:- Super conductors acts as conductors at room temperature, but when cooled below Tc, the molecular motion with in the material reduces enough that the flow of current move unimpeded.
Type II:- superconductors are not particularly good conductors at room temperature, the transition to a super conductor state is more gradual than Type I superconductors. The mechanism and physical basis for this change in state is not at present, fully understood Type II superconductors are typically metallic compounds and alloys.(b) Varnish is a transparent, hard, protective finish or film. Primarily used in wood finishing but also for other material. Varnish is traditionally a combination of drying oil, a resin & a thinner or a solvent. Varnish finishes are usually glossy but may produce stain.
Characteristics:-
(1) It should dry rapidly.
(2) It should form a hard film on drying.
(3) It should be durable and weather resistant.
(4) It should not crack on drying.
(5) It should not hide the natural grace of the inner surface of timber.
(6) The color of varnish should not fade away with time.
(c) The film lubrication is transition region between elastohydrodynamic lubrication and boundary lubrication. A technique of relative optical interference intensity with the resolution of 0.5nm in vertical direction & 1.5µm in the horizontal direction is used in pure rolling process to measure the film thickness with different lubricants speeds, loads and substrate energy.Q6 (a) Give the preparation and uses of following polymers:
(i) PVC (ii) Teflon (iii) Buna-S
(b) What is air pollution? What are its main sources? How can we prevent it?Answer:
(a) (i) PVC (Polyvinyl Chloride):- Vinyl chloride (monomer) and water are introduced into the reactor & a polymerization indicator, along with other additives. It is an endothermic reaction.
Uses:-
(1) It is used for making sewage pipes.
(2) It is used for manufacturing window & door frames.
(3) It is also used for cabling application as a wire insulator.(ii) Teflon:- It is plastic like substance which is produced by polymerizing tetrafluoroethylene (CF2=CF2). It is formed when chloroform is treated with the hydrofluoric acid and antimony trifluoride.
HF/SbF3CHCl3---------------> CHF2Cl--------------------> CF2=CF2
n [CF2=CF2] -----------> --[--CF2-CF2---]—
Uses:-
(1) PTFE is usually used to coat in the non-stick frying pans as it has the ability to resist high temperature.
(2) It is used as a film interface.
(3) It is widely used in medical synthesis, test & many more medicines.(iii) Buna –S:- It is also known as styrene-butadiene. Buna-S is name derived from butadiene & Na- sodium/ natrium & S- styrene. It is derived from two monomers; styrene and butadiene.
[CH2=CH-CH=CH2]n + [CH3-CH2]m -----à -[-CH2-CH=CH-CH2-CH2-CH2]-
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Butadiene Styrene Buna S
Uses:-
(1) It is used for manufacture of passenger car tyres, motorcycle tyre, scooter tyre, etc.
(2) It is also used for manufacturing of conveyor belts, footwears & other goods, etc.
(b) Air pollution is a mixture of particles & gases that can reach harmful concentration both outside & indoors. Its effects can range from higher disease risks to rising temperature. Smoke, mold, soot, pollen, methane & carbon dioxide are just few examples of common pollutants.
Sources:- Four main types of sources
(i) Mobile sources; such as cars, buses, planes, trucks & trains.
(ii) Stationary sources: such as power plants, oil refineries, industrial facilities & factories.
(iii) Area sources: such as agricultural areas, cities & wood burning fire places.
(iv) Natural sources: such as wind blown, dust, wild fires & volcanoes.Prevention:
(i) Conserve energy at home, at work, everywhere.
(ii) Consider using the gas logs instead of wood.(iii) Reduce the use of private vehicles & use public transport instead.
(iv) Stop cutting the trees.
(v) Avoid burning leaves, trash and other material.
(vi) Reduce the use of fire place & wood stove.Q7 (a) Calculate the gross calorific value of coal (using Dulong’s formula) having the
following percentage composition.
C = 80% , H = 7% , O = 3% , S = 3.5% , N = 2.1% , and Ash = 4.4%
(b) Explain addition and condensation polymerization with suitable example in
each case.
(c) Explain green house effect and global warming.Answer:
(a) GCV or HCV =1/100 [ 8080C + 34500(H-O/8)+22400s]
= 1/100[8080 x80 +34500 (7-3/8+ 22400 x3.5]
=1/100 [646400+228562.50+78400]
=1/100[953362.50]
= 9533.62 cal/kg(b) Addition polymerisation is addition of polymers. The repeating monomers units form a linear of structure depending on the type of monomer. During addition polymerization, the monomer rearranges themselves to form a new structure. But there is no loss of an atom or a molecule.
Like PVC polymerisation
nH2C=CHCl ---à [H2C-CHCl]n
Condensation polymerisation is that in which two monomer attached & there is loss of any small molecule during the polymerisation. (Small molecule like H2O, etc.)
0 0 0 0
n HO- C?-R- C?-OH + nH2N-R’-NH2 ---à -[-C?-R- C?-NR’H-NH-]n- +2H2O
(c) Global Warming:- Scientist interchange the term global warming with climate change. Although temperature rises in certain areas but the ocean current move the heat around in different parts of the globe. As a result of which some regions experience cooler climate and some experience warmer weather. Therefore, climate changes vary in different regions. Hence, the term climate change is generally used by scientists instead of global warming.
Earth surface has the ability to absorb almost 75% of the entire solar energy. This is responsible for the increase in temperature. However, part of the energy is given back to the atmosphere in the form of radiation. There are certain gases that have the ability to trap heat and restrict the heat from escaping from the atmosphere. These gases are called Greenhouse gases.Greenhouse effect:- It is a phenomenon by which the radiations comes from the sun is trapped in the Earth’s atmosphere by the greenhouse gases. There greenhouse gases are making layer or blanket around the earth’s surface and trapped by the blanket of greenhouse gases. The main greenhouse gases which cause global warming is Carbon dioxide(CO2), Ozone(O3), Chlorofluoro Carbons (CFC), Methane(CH4), etc.