CENTRAL INSTITUTE OF PLASTICS ENGINEERING & TECHNOLOGY
Question Bank Solution
2 MARK ---QUESTION
COURSE : DPMT
SEMESTER: II
SUBJECT : Engineering Chemistry
4/5 MARK—QUESTION
-------
Ques 1: Explain Constituents of the atom and Rutherford model of atom.
Ans: Atomic structure refers to the structure of atom comprising of a nucleus (center) in which the protons (positively charged) and neutrons (neutral) are present. The negatively charged particles called electrons revolve around the center of the nucleus.
Rutherford Atomic Theory: Rutherford, a student of J. J. Thomson modified the atomic structure with the discovery of another subatomic particle called “Nucleus”. His atomic model is based on the Alpha ray scattering experiment.
Alpha Ray Scattering Experiment: A very thin gold foil of 1000 atoms thick is taken. Alpha rays (doubly charged Helium He2+) were made to bombard the gold foil. ZnS screen is placed behind the gold foil.
Observations:
Most of the rays just went through the gold foil making scintillations (bright spots) in the ZnS screen.
A few rays got reflected after hitting the gold foil.
One in 1000 rays got reflected by an angle of 180° (retraced path) after hitting the gold foil.
Conclusions:
Since most rays passed through, Rutherford concluded that most of the space inside the atom is empty.
Few rays got reflected because of the repulsion of its positive with some other positive charge inside the atom.
1/1000th of rays got strongly deflected because of a very strong positive charge in the center of the atom he called this strong positive charge as “nucleus”.
He said most of the charge and mass of the atom resides in the Nucleus
Limitations of Rutherford Atomic Model
If electrons have to revolve around the nucleus, they will spend energy and that too against the strong force of attraction from the nucleus, a lot of energy will be spent by the electrons and eventually, they will lose all their energy and will fall into the nucleus so the stability of atom is not explained.If electrons continuously revolve around the ‘nucleus, the type of spectrum expected is a continuous spectrum. But in reality, what we see is a line spectrum.
Ques2: Explain Heisenberg Uncertainty principle.
Ans: Heisenberg’s Uncertainty principle states that it is inherent uncertainty in the act of measuring a variable of a particle. The principle is applicable to the position and momentum of a particle. According to the principle, more precisely the position is known, the more uncertain is the momentum and vice versa.Heisenberg uncertainty equation is --- Δp x Δx≥ h / 4π
Where Δp = uncertainty in momentum, Δx = uncertainty in position, h = Plank constant
Question 3: What do you mean by quantum number?
Ans: Quantum number gives complete address of an Electron. Four quantum numbers can be used to completely describe all the attributes of a given electron belonging to an atom, these are:
Principal quantum number, denoted by n.
Orbital angular momentum quantum number (or azimuthal quantum number), denoted by l.
Magnetic quantum number, denoted by m1.
The electron spin quantum number, denoted by ms.
Ques 4: Write all 4 quantum numbers for last electron of Sodium atom and sodium ion..
Ans: Na(11) = 1s2,2s2,2p6.3s1 here last electron present in 3s1
All 4 quantum no. values for last electron is ---- n = 3, l = 0, m = 0 , s = +1/2
Na+ ion configuration is --- 1s2,2s2,2p6. (one electron remove from outermost shell)
Now last electron is in 2p6….last electron of 2p6 is the last electron of Na+ ion
For last electron of 2p6 all 4 quantum number are --- n = 2, l = 1, m = +1, s = -1/2.
Ques 5: Define Lewis electron dot structure with suitable examples.
Ans: Lewis dot structures also called electron dot structures are diagrams that describe the chemical bonding between atoms in a molecule. They also display the total number of lone pairs present in each of the atoms that constitute the molecule. Lewis dot structures are commonly referred to as electron dot structures or Lewis structures. Lewis defined a base as an electron pair donor and an acid as an electron pair acceptor.
electron dot formula for the carbonate ion is --
Ques 6: What do you mean by dilution? Explain the strength of acids and bases.
Ans: Dilution :Dilution is the process of reducing the concentration of a solution by adding more solvent To it.It is a highly exothermic process.To dilute acid, the acid must be added to water and not the other way round.
Strength of acids and bases
Strong acid or base: When all molecules of a given amount of an acid or a base dissociate completely in water to furnish their respective ions, H+(aq) for acid and OH−(aq) for base). Strong acids furnishes more no of H+ ions per unit volume of solution & has very low pH and strong base furnishes more no of OH- ion per unit volume of solution with high pH.
Weak acid or base: When only a few of the molecules of a given amount of an acid or a base dissociate in water to furnish their respective ions, H+(aq) for acid and OH−(aq) for base).
Ques 7: Define Dilute and Concentrated solution.
Ans: Dilute acid: contains less number of H+(aq) ions per unit volume.
Concentrated acid: contains more number of H+(aq) ions per unit volume.
Ques 8: Calculate the molality of a solution where 0.5 grams of toluene (C7H8) is dissolved in 225 grams of Benzene(C6H6). Calculate the moles of given solute.
Ans: Toluene: Molecular weight = C7H8=7×12+1×8=92 grams/mole, Using the formula -----
Moles of Toluene = Mass in grams / Molecular weight = 5.0 grams / 92 grams/mole = 0.054 mole.
So, the mole of toluene is 0.054 mole.
Now calculate the kilogram of solvent.225 grams ofBenzene1000=0.225 kilogram
As the final step, calculate the molality using the formula-----
Molality(m)=Moles of Toluene /Mass of Benzene in grams
Molality(m)= 0.054 moles / 0.225 kg Molality(m)=0.24 m
Ques: 9 Write the formula of acid buffer and base buffer. How to calculate pH of buffer solution?
Ans: Acidic Buffers ---
As the name suggests, these solutions are used to maintain acidic environments. Acid buffer has acidic pH and is prepared by mixing a weak acid and its salt with a strong base. An aqueous solution of an equal concentration of acetic acid and sodium acetate has a pH of 4.74.
pH of these solutions is below seven
These solutions consist of a weak acid and a salt of a weak acid.
An example of an acidic buffer solution is a mixture of sodium acetate and acetic acid (pH = 4.75).
Alkaline Buffers---
These buffer solutions are used to maintain basic conditions. Basic buffer has a basic pH and is prepared by mixing a weak base and its salt with strong acid. The aqueous solution of an equal concentration of ammonium hydroxide and ammonium chloride has a pH of 9.25.
The pH of these solutions is above seven
They contain a weak base and a salt of the weak base.
An example of an alkaline buffer solution is a mixture of ammonium hydroxide and ammonium chloride (pH = 9.25).
pH of acid buffer = pKa + ([salt]/[acid])
The equation is the Henderson-Hasselbalch equation, popularly known as the Henderson equation.
Ques 10: Explain the Lime soda method of removal of permanent hardness of water.
Ans: Soda lime is a process used in water treatment to remove Hardness from water. This process is now obsolete but was very useful for the treatment of large volumes of hard water. Addition of lime (CaO) and soda (Na2CO3) to the hard water precipitates calcium as the carbonate, and magnesium as its hydroxide. The amounts of the two chemicals required are easily calculated from the analysis of the water and stoichiometry of the reactions. The lime‐soda uses lime, Ca (OH)2 and soda ash, Na2CO3, to precipitate hardness from solution. In this process CO2 and bicarbonates of Ca & Mg are complexed
by lime. In this process Calcium and Magnesium ions are precipitated by the addition of lime (Ca(OH)2) and soda ash (Na2CO3).
Ca(OH)2 + CO2 → CaCO3 ↓ + H2O....
Ca(OH)2 + Mg(HCO3 )2 → MgCO3 + CaCO3 ↓ + 2H2O.....
Lime addition removes only magnesium hardness and calcium carbonate hardness. In equation 5 magnesium is precipitated, however, an equivalent amount of calcium is added. The water now contains the original calcium non-carbonate hardness and the calcium non-carbonate hardness produced. Soda ash is added to remove calcium non-carbonate hardness.
To precipitate CaCO3 requires a pH of about 9.5; and to precipitate Mg(OH)2 requires a pH of about 10.8, therefore, an excess lime of about 1.25 meq/l is required to raise the pH.
The amount of lime required: lime (meq/l) = carbon dioxide (meq/l) + carbonate hardness (meq/l) + magnesium ion (meq/l) + 1.25 (meq/l)
The amount of soda ash required: soda ash (meq/l) = non-carbonate hardness (meq/l)
After softening, the water will have high pH and contain the excess lime and the magnesium hydroxide and the calcium carbonate that did not precipitate. Recarbonation (adding carbon dioxide) is used to stabilize the water. The excess lime and magnesium hydroxide are stabilized by adding carbon dioxide, which also reduces pH from 10.8 to 9.5.
Limitation: Lime soda softening cannot produce a water at completely free of hardness because of the solubility (little) of CaCO3 and Mg(OH)2. Thus the minimum calcium hardness can be achieved is about 30 mg/L as CaCO3, and the magnesium hardness is about 10 mg/L as CaCO3. We normally tolerate a final total hardness on the order of 75 to 120 mg/L as CaCO3, but the magnesium content should not exceed 40 mg/L as CaCO3 (because a greater hardness of magnesium forms scales on heat exchange elements).
Ques 11: How can we remove the permanent hardness of water by Permutit method.
Ans: Hardness is defined as the soap consuming capacity of a water sample. Generally, soaps consist of the sodium salts of long fatty acids (such as oleic acid, palmic acid and stearic acid). The soap consuming capacity of a water largely due to the presence of Ca+2 and Mg+2 ions as they form insoluble scums of calcium and magnesium soaps which do not have any detergent value.For softening of water by zeolite process, hard water is percolated at a specified rate through a bed of zeolite. Zeolite holds sodium ion loosely and can be represented as Na2Z, where Z represents insoluble radical frame work.When the water passes through the zeolite the hardness causing ions (Ca+2, Mg+2 etc.) are retained by the zeolite as CaZ and MgZ respectively, while the outgoing water contains equivalent amount of sodium salts. The block diagram and chemical reactions taking place in zeolite softener are:
After some time, when the
zeolite is completely changed into calcium and magnesium zeolites, then it gets
exhausted (saturated with Ca+2 and Mg+2 ions)
and it ceases to soften water. It can be regenerated and reused by treating it
with a 10% brine (sodium chloride) solution.
CaZ
+
2NaCl ® Na2Z +
CaCl2
MgZ
+
2NaCl ® Na2Z +
MgCl2
Ques 12: Compare the merits and demerits of ion exchange process and zeolite process used for water softening.
Ans:Merits
of ion-exchange
process:
Ø The process can be
used to soften highly acidic or alkaline water.
Ø It produces water
of very low hardness (say 2ppm).
Ø It is very good
for treating water for use in high-pressure boiler.
Demerits
of ion-exchange
process:
Ø The equipment is
costly and more expensive chemicals are needed.
Ø If water contains
turbidity, then the output of the process is reduced
Ø Turbidity must be
below 10 ppm. If it is more, it has to be removed first by coagulation and
filtration.
Merits
of Zeolite Process:
Ø It removes the
hardness almost completely (about 10 ppm hardness only).
Ø The process
automatically adjust itself for variation in hardness of incoming water.
Ø This process does
not involve any type of precipitation, thus, no problem of sludge formation
occurs.
Demerits
of Zeolite Process:
Ø The outgoing water
(treated water) contains more sodium salts.
Ø This method only
replaces Ca+2 and Mg+2 ions by Na+ ions.
Ø High turbidity water cannot be softened efficiently by zeolite process.
Ques 13: Write short note on --- i) catenation ii) Functional group
Ans: Catenation: It can be
defined as the self-linking of atoms of
an element to form chains and rings. This
definition can be extended to include the formation of layers like
two-dimensional catenation and space lattices like three-dimensional catenation.
Examples of Catenation
The most common examples of
catenation or elements that exhibit catenation are: Carbon, Silicon, Sulfur
& Boron.
Catenation occurs most readily
in carbon, forming covalent bonds to form longer chains and structures with
other carbon atoms. This is why the vast number of organic compounds are found
in nature. Carbon is best known for its catenation properties, with the
analysis of catenated carbon structures in organic chemistry.Carbon is by no
means the only element capable of forming such catenae, however, and several
other main group elements are capable of forming a wide range of catenae,
including silicon, sulfur, and boron.
All the elements of carbon
family or group 4 family exhibit catenation property. The first member from the
family has the highest tendency to catenate.
Following is the tendency to catenate:
|
C > Si >Ge>Sn>Pb |
Catenation tendency decreases
down the group. This happens because the atomic size increases down the group
and the strength of the covalent bond decreases. Hence, the catenation property
decreases down the group.
Functional
group :A functional group is an individual atom or a compound formed in
a unique manner. A functional group is the most reactive site in an organic
molecule. Compounds with a similar functional group have
the similar type of reactions.
|
Functional Group and
Formula |
Suffix |
Example |
|
Alcohol, R-OH |
-ol |
Methanol |
|
Ketone, R-(CO)-R’ |
-one |
Butanone |
|
Aldehyde, R-CHO |
-al |
Ethanal (acetaldehyde) |
|
Carboxylic Acid, R-COOH |
-oic acid |
Ethanoic Acid (acetic
acid) |
Ques14: Differentiate between ---- i) saturated and unsaturated hydrocarbon ii) homocyclic and heterocyclic compounds
Ans: i) Saturated
Hydrocarbons: In these compounds, carbon-carbon atoms and carbon-hydrogen
atoms are held together by single bonds. These single bonded compounds are the
simplest hydrocarbons. These types of hydrocarbons don’t have double or triple
bonds. In terms of hybridization, they
have Sp3 hybridised carbon atom with no Sp2 or
Sphybridised Carbon atoms. They are together called as alkanes which have a
general formula CnH2n+2. For example, CH4C3H6.
Unsaturated Hydrocarbons: These compounds consist of a single, double or a triple bond between carbon-carbon atoms. The double-bonded compounds are called alkenes and the triple bonded compounds are called alkynes. The general formula for alkenes is CnH2n and for alkynes the general formula is CnH2n-2.
ii) Homocycliccompounds : these
are containgaring structure in which frame work of ring is made up of only
Carbon atoms. These cycloalkanes,
Benzenoid compounds and non benzenoid compounds.
Heterocyclic compounds: these are containing
an hetero aton like, N,O,X in ring frame work .these hetro atom replace the
ring caron.
Ques 15: Explain the classification of Organic compound with example.
Ans: Classification
of Organic Compounds Based on Structure -----
Examples – Open chain compounds
= Alkanes, Alkenes, alkynes( methane, ethane, acetylene)
Close chain compounds –i) homocyclic = cycloalkanes, aromatic compounds
( cyclohexane, benzene, phenol,)
ii) heterocyclic = (pyridine, pyrrole, furan, thiophene)
Ques 16: Write the IUPAC name of following compounds ----
i) (CH3)3 C CH2 CH (CH3)2 ii) CH3 CH=CH CH(Cl) CH3 iii) CH2=CH C(Cl)(Br) CH=CH2
iv) CH3CH(OH) CH=CH2 v) CH3 CH2 CH(OH) CH2 CO CH3 vi) COOH CH2CH2COOH
Ans: i) 2,2,5-trimethyhexane II) 4-Chloropent-2-ene iii) 3-Bromo-3-chloropent-1,4-diene
iv) but-3-en-2-ol v) 4-hydroxyhexan-2-one vi) butane-1,4-dioic acid
Ques 17: Give the IUPAC names of the following compounds:
Ans: a) 3–phenyl propane (b) 3–methylpentanenitrile (c) 2, 5–dimethyl heptane
(d) 3–bromo–3–chloroheptane (e)
3–chloropropanal
Ques 18: What do you mean by natural gas? Mention its uses and advantages.
Ans: Natural Gas is mainly extracted from the petroleum deposits deep beneath the earth. In fact, it occurs just above the layer of crude oil, as gases are lighter than oil. It is formed through the same process through which petroleum is formed. High temperatures and pressure leads to the conversion of the remains of plants and animals buried under the earth into naturally occurring gas along with petroleum and coal.
Uses of Natural Gas :
Natural Gas was used mainly for street and
household lighting in the 19th and 20th century.
Now, it has a lot more uses in the homes and
industrial applications.
It is used to turn turbines for wind and
solar energy generation.
This fossil fuel is used for the production
of ammonia which itself is used for making fertilizers.
It is a domestic fuel as well. It fires
stoves in our houses and also runs heaters, ovens, boilers, etc.
Compressed Natural Gas or CNG, that is gas
stored at high pressure, is also used in some households for heating and
cooking purposes.
CNG is also a cheap and environment friendly
alternative for a transportation fuel used in low load vehicles requiring high
fuel efficiency.
Liquefied Natural Gas or LNG is used to power
vehicles such as off-road trucks and trains.
Advantages of Natural
Gas:
Natural Gas is a cleaner fuel. It is less
harmful to the environment than coal, petrol or diesel as it has less carbon
dioxide emissions.
It can be easily stored and transferred
through pipelines.
It is relatively more abundant than other
fossil fuels i.e. coal and petroleum.
It is also a safer fuel, as it is lighter
than air and dissipates rather than exploding.
It provides instant energy, which is why it is used in oven cooking, as it does not require pre-heating.
Ques 19: Define corrosion and factors affecting corrosion.
Ans: Corrosion: It is defined as the natural process that causes the
transformation of pure metals to undesirable substances when they react with
substances like water or air. This reaction causes damage and disintegration of
the metal starting from the portion of the metal exposed to the environment and
spreading to the entire bulk of the metal.
Factors Affecting Corrosion
1. Exposure of the metals to
air containing gases like CO2, SO2, SO3 etc.
2. Exposure of metals to
moisture especially salt water (which increases the rate of corrosion).
3. Presence of impurities like
salt (eg. NaCl).
4. Temperature: An increase in
temperature increases corrosion.
5. Nature of the first layer of
oxide formed: some oxides like Al2O3 forms an
insoluble protecting layer which can prevent further corrosion. Others like
rust easily crumble and expose the rest of the metal.
6. Presence of acid in the atmosphere: acids can easily accelerate the process of corrosion.
Ques 20: Explain the methods of prevention of corrosion.
Ans: Prevention of
Corrosion:
Preventing corrosion is of
utmost importance in order to avoid huge losses. Majority of the structures we
use are made out of metals. This includes bridges, automobiles, machinery,
household goods like window grill, doors, railway lines, etc.
There are various methods to
prevent corrosion. These include,
1.
Electroplating
It is the process by which a
metal (I) is coated with a thin layer of another metal (II) using electrolysis.
In this way, the new metal coating protects the metal (I) from corrosion.
In the process, a metal is used
as the coating, (metal II) is kept as the anode and metal (I) (metal to be
plated) is kept as the cathode. i.e, metal ‘I’ is connected to the negative
terminal and metal II is connected to the positive terminal. These 2 electrodes
are immersed in an electrolyte and when power is supplied, oxidation happens in
the anode, thereby dissolving metal II ions in the electrolyte. These dissolved
metal II ions are reduced at the cathode thereby providing a coating on metal
I.
The metals most commonly used
as the anode are Copper, Nickel, Gold, Silver, Zinc. Etc.,
2.
Cathodic Protection
In this process, the base metal
is connected to a sacrificial metal that corrodes instead of the base metal. By
doing so this sacrificial metal (which is more reactive than the base metal)
will give out electrons and get oxidised. The ions thus formed takes part in
the corrosion reactions thereby saving the base metal.
3.
Galvanization
This process involves coating
iron with a thin layer of zinc. It is generally done by dipping iron in molten
zinc. The zinc layer coating thus protect the iron inside from corrosion
4.
Painting and Greasing
Providing a layer of paint or
grease on the metal can prevent the exposure of the metal with the external
environment thereby preventing corrosion.
5. Choosing the right material
can also help prevent corrosion. E.g: Aluminium and stainless steel are highly
corrosion resistant
6.
Using corrosion Inhibitor
Corrosion inhibitors are chemicals which when added to the corrosion environment has the ability to cut down the rate of corrosion.
Ques 21: Explain the EDTA method of determination of hardness of water.
Ans: EDTA (Ethylenediamine tetra acetic acid) forms colorless stable complexes with Ca2+ and Mg2+ ions present in water at pH = 12 To maintain the pH of the solution at 12 buffer solution (NH4Cl + NH4OH) is used. Eriochrome Black-T (E.B.T) is used as an indicator. The sample of hard water must be treated with buffer solution and EBT indicator which forms unstable, wine-red colored complex with Ca2+ and Mg2+ present in water.which on addition of EDTA gives blue colour stable complex.
EBT/ pH
12 EDTA
Ca++ / Mg++ Ca++ --EBT Ca++
--EDTA &
& Mg++ --EBT - EBT Mg++ --EDTA
(Hard water) (Wine red
unstable complex) (Blue
stable complex)
Ques 22: Differentiate between Galvanic cell and Electrolytic cell.
Ans: Galvanic Cells vs Electrolytic Cells
|
Galvanic Cells |
Electrolytic
Cells |
|
Spontaneous redox reactions convert the
chemical energy to an electric energy |
Non-spontaneous redox reactions convert the
electric energy to a chemical energy |
|
Electric energy is generated by redox
reactions |
Electric energy brings about the chemical
reaction with the help of an external source |
|
The cathode is the positive electrode and
anode is the negative electrode |
The anode is the positive electrode and
cathode is the negative electrode |
|
The process of oxidation takes place at the
anode and the reduction process occurs at the cathode |
Here, the oxidation process occurs at the
cathode while the reduction process takes place at the anode |
|
Half cells are set up in different
containers and are connected through salt bridges |
Electrodes are kept in the same container
in a molten or solution electrolyte |
|
Application lies in Batteries |
Application lies in purifying copper and
electroplating |
Ques 23: Draw a neat and clean, well labeled diagram of electrochemical cell.
Ans:
Electrochemical cells generally consist of a cathode and an anode. The key features of the cathode
and the anode are tabulated below.
|
Cathode |
Anode |
|
Denoted by a positive sign since electrons
are consumed here |
Denoted by a negative sign since electrons
are liberated here |
|
A reduction reaction occurs in the cathode
of an electrochemical cell |
An oxidation reaction occurs here |
|
Electrons move into the cathode |
Electrons move out of the anode |
Ques 24: Explain the heat and work concept with expression.
Ans: Work:
Work done by a system is defined as the quantity of energy exchanged between a system and its surroundings. Work is completely governed by external factors such as an external force, pressure or volume or change in temperature etc.
Heat:
Heat in thermodynamics is
defined as the kinetic energy of the molecules of the substance. Heat and the
thermodynamics together form the basics which helped process designers and
engineers to optimize their processes and harness the energy associated with
chemical reactions economically. Heat energy flows from higher temperature to
lower temperature.
|
If energy enters the system, its sign
is positive. |
Ques 25: Differentiate between reversible and irreversible process.
ans: Reversible
and Irreversible processes
Reversible
Process
A thermodynamic process is reversible if the
process can be turned back such that the system and surroundings return to
their original states, with no other change anywhere else in the universe.
This means in the Reversible processes if a
process starts from initial state then it goes to final state and then it can
reversed back from final state to initial state.
Examples:- Isothermal expansion and
compression, Electrolysis
A process is reversible if :-
It is quasi-static
No dissipative forces (that is no loss of
heat by friction etc.).
Both initial and final states of the system are in thermodynamic equilibrium with each other.
Irreversible
Process
Irreversible processes are those that cannot
be reversed.
Two causes which give rise to irreversible
processes
Irreversible processes takes place at a very
fast rate.
Dissipative Effects.
Examples:-Plastic deformation, Combustion, Diffusion, Falling of water from hill.
Ques 26: Explain various thermodynamic processes.
Ans: The state variables(T,P,V,n) in a
thermodynamic process are defined only when the thermodynamic system is in
equilibrium with the surrounding. So a process in which at each moment the
system is in thermodynamic equilibrium with the surrounding is known as a
quasi-static process.
The
Thermodynamic Processes
(a) Isothermal Process: It
is a thermodynamic process in which temperature remains constant.we know
internal energy only depends on temperature. As the temperature is constant
hence ∆U = 0. So from first law of thermodynamics,
∆U = Q – W, Q = W
(b) Adiabatic Process: It
is a thermodynamic process in which no heat is exchanged between the system and
the surrounding. So, Q = 0.For adiabatic process,
ΔU=−W
So if work
done is
negative internal energy increases and vice versa.
(c) Isochoric Process: In isochoric
process the change in volume of thermodynamic system is zero. As change in
volume is zero so work done is zero. From First law,
Q=ΔU
(d) Isobaric Process: The
pressure remains constant during this process. So ,
W=P (Vf−Vi)
So if volume increases work done is positive
else negative.
(e) Cyclic Process: It is a process in which the final state of the system is equal to initial state. As we know Change in internal energy is state function so in this case ∆U = 0.
Ques 27: Explain the advantages and disadvantages of gaseous fuel.
Ans:
Gaseous fuels occur in nature, besides being manufactured from solid and
liquid fuels. Most gaseous fuels are composed of hydrocarbons, carbon monoxide,
hydrogen or a mixture of them all.
Advantages:
Transportation through pipes is easy.
Sparking combustion is really easy.
They have a higher heat content.
Clean after use.
Do Not require any special burner technology.
Disadvantages:
Large storage tanks required.
As they are highly inflammable, the chance for fire hazards are extremely high and strict safety measures need to be followed.
Ques 28: Mention the advantages and disadvantages of liquid
fuels.
Ans: Most liquid fuels are derived from the
fossilized remains of dead plants and animals by exposure to heat and pressure
in the Earth’s crust. The fumes of the liquid fuel are flammable instead of the
liquid.
Advantages:
Higher calorific value per unit mass.
Burn without ash, clinkers, etc.
Controlling the combustion is easier.
Transportation easier through pipes and
stored indefinitely without loss.
Loss of energy is comparatively lower.
Require less furnace space for combustion.
Disadvantages:
Cost of liquid fuel is much higher compared
to solid fuel.
Storage methods are costlier.
Greater risk of fire hazards.
Special burning equipment required for more efficient combustion.
Ques 29: Explain the advantages and disadvantages of solid fuels.
Ans: Fuels which are found in their solid
state at room temperature are generally referred to as Solid Fuels. They were
the first kind of fuel known to be used by man, basically wood to create fire.
Coal was another one of the influential fuels known to man as it leads the way
for the industrial revolution, from firing furnaces to running steam engines.
Advantages:
Easier transportation and storage.
Low production cost.
Moderate ignition temperature.
Disadvantages:
Large portion of energy is wasted.
Cost of handling is high and controlling is
also hard.
Ash content is high & burn with clinker formation.
Ques 30: What do you mean by thermodynamics? Define system and surrounding.
Ans: The branch which deals with the the movement
of energy from one form to the other and the relation between heat and
temperature with energy and work done is called as thermodynamics. In other
terms we can define thermodynamics as the science stream that deals with the
study of the combined effects of heat and work on the changes of state of
matter confined by the laws of thermodynamics. Chemical reactions which
releases heat energy associated with it are converted into different usable
forms based on the laws of thermodynamics. The fact that energy can only be
transformed from one form to the other forms and its use in different
industries is on the basis of energy transformation. We are aware that chemical
reactions have energy associated with it. The laws of thermodynamics deal with
energy changes during a reaction and are not concerned with the rate at which
the reaction is proceeding.
Chemical thermodynamics is the
study of relation between work, heat and chemical reactions or with the
physical changes of the state which are confined to the laws of thermodynamics.
System = A system as the part of the universe under study that
is the part where observations are made. The surrounding and universe interact
with each other and depending on the type of the system, exchange of matter and
energies occur. The system’s classification entirely depends on the movement of
energy and matter in or out of the system.
Surrounding =
Except system rest part of the universe considered as surrounding. The heat
exchange always takes place between system and surrounding.
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