“Develop success from failures. Discouragement and failure are two of the surest stepping stones to success.”
CHEMISTRY
CHAPTER - 1
Structure of atom
Rutherford model of the structure of atom
According to this principle / model of atom, atom is like a sphere having a heavy mass core in centre called nucleus.
Nucleus contains neutron and proton and negatively charged electrons revolving around the nucleus out of positive charge on nucleus & negative charge on electron, then the atom becomes neutral.
Drawback → According to this theory electron is revolving continuously around the nucleus but if it revolve continuously will losing its energy & finally falls into nucleus, which does not specify structure of atom.
Bohr’s model of atom
It is same of Rutherford model of atom but it defines that the electron revolves in certain energy level called orbital. While revolving in these orbit they do not decrease their energy. If they lose this energy they will not fall in nucleus.
And he gave the formula for determine the number of electron in each orbital with 2n² where n is the number of orbital.
k = 1 2(1)² = 2 L = 2 2(2)² = 8 M = 3 2(3)² = 18 N = 4 2(4)² = 32
According to this theory, electrons of hydrogen atom jump from lower energy level to higher energy level in excited state and while coming it discrete energy of different wavelength, which is given by:
Electronic configuration → The distribution of electrons in various orbital in an atom is known as electronic configuration of atom. The filling of electrons in various orbitals is governed by the following rules:
This principle states that, in the ground state of atom the electrons are filled in the various orbitals in order of their increasing energy. 1s, 2s, 2p, 3s, 3p, 4s …
It states that the number of two electrons in an atom can have the same set of all quantum numbers. (No two electrons in an atom can have the same set of four quantum numbers.)
It states that pairing of electrons in the orbital of subshell cannot take place until all the orbitals of the given subshell are singly occupied, and the singly occupied orbitals must have electrons with parallel spin.
Example: 3p³ ↑ ↑ ↑
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² …
(Top, faint electronic configuration line) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² – … (partly cut)
Quantum number → It is the set of four quantum numbers which gives the exact position of an electron moving in an atom.
or
It is the postal address of an electron.
There are four types of quantum number:
(i) Principal quantum number → This quantum number determines the number of shell of electron movement.
(ii) Azimuthal quantum number → It determines the number of subshell of electron movement.
(iii) Magnetic quantum number → It determines the special arrangement / energy of an atom or magnetic behaviour of electron.
(iv) Spin quantum number → It determines spin quantum number of an electron. It may be:
For s: ↑↓
For p (three boxes): ↑↓ ↑↓ ↑↓
For d (five boxes): ↑↓ ↑↓ ↑↓ ↑↓ ↑↓
De-Broglie equation → According to this principle the light has dual nature, means it can act as a particle as well as wave.
λ= {h}/{mv}
where
Energy of photon – Planck:
E = hν----(1)
Einstein equation:
E = mc2---(2)
From eq. (1) and (2):
hν=mc2 \
mcλh = mc
λ=h/mc
λ=h/mv hence proved
Heisenberg uncertainty principle → According to this principle it is impossible to determine exact position & exact momentum of a fast moving electron in an atom.
Mathematically,
Δx⋅ΔP≥h/4π
Where, Delta x Δx = uncertainty in position Delta PΔP = uncertainty in momentum h = Planck constant
But P=mv
Δx⋅Δv = h/4πm
CHAPTER - 2
Periodic properties of an element
Dobereiner triads → According to this law if the elements are arranged in increasing number of their atomic mass then atomic mass of the middle element was arithmetic mean of other two elements.
Example:
Li (7) Na (23) K (39)
Limitation →
Newlands’ law of octaves → According to this law, if the elements are arranged in increasing number of their atomic mass then property of first element was similar to the eighth element.
Mendeleev periodic law → According to this law periodic properties of element are the periodic function of their atomic mass.
Merits →
Modern periodic law → According to this law periodic properties of element are the periodic function of their atomic number.
Periodic properties
(1) Atomic radii or size → It is the distance from centre of nucleus of an atom to the outermost shell of electron.
Variation → It increases on going top to bottom in periodic table.
→ These are the elements in which the last electron enters the s-subshell of the outermost principal energy level. → It includes elements of group 1 and group 2 known as alkali metals and alkaline earth metals.
→ These elements are soft metals. → They have low melting point and boiling point.
→ They have low density. → They are reactive metals and form ionic compounds. → Their hydroxides are generally soluble in water.
These are the elements in which the last electron enters the p-sub shell of the outermost energy level. These elements lie on the right-hand side of the periodic table and include elements of group 13th to 18th of the periodic table.
→ They consist mostly of metals, non-metals, and metalloids. → They form covalent as well as ionic compounds. → Some of them are good oxidising agents. → Some of them form acidic oxides. → They do not impart any colour to the flame. → They show variable oxidation states.
These are the elements in which the last electron enters the d-sub shell of the outermost energy level. These are those complete rows in which ten elements in each row and include elements of group 3 to 12 of the periodic table. These are called transition elements.
→ These are hard metals in nature. → They have high melting point.
These are the elements in which the last electrons enter the f-subshell of the outermost energy level. They consist of two series of fourteen elements each. Both series are placed separately at the bottom of the periodic table. The elements of the first series are called lanthanides and the elements of the second series are called actinides.
CHAPTER - 3
Chemical Bond → The bond which is formed by chemically combining two or more atoms of molecules are called chemical bond.
Ionic bond or electrovalent bond → The bond formed by transfer of electron from metal to a non-metal is called ionic bond.
Example: Na → Na⁺ + e⁻ 2,8,1 → 2,8
Cl + e⁻ → Cl⁻ 2,8,7 → 2,8,8
Na⁺ + Cl⁻ = NaCl
(i) Physical state → Ionic compounds are generally found in solid state because of good force of attraction.
(ii) Solubility → Ionic compounds are soluble in water but insoluble in petrol, kerosene, alcohol etc.
(iii) Electrical conductivity → Ionic compounds do not conduct electricity in solid state but they conduct electricity in molten state.
(iv) Melting and boiling point → Ionic compounds have high melting and boiling points due to the heavy force of attraction.
Example: (Hand-drawn diagram of H–H) = H₂
(Hand-drawn diagram of Cl–Cl) = Cl₂
Examples: H–Cl → HCl H–H → H₂
Example: O=O → O₂
Example: N≡N → N₂
(i) Physical state → The covalent compounds are generally found in liquid or gaseous form.
(ii) M.P and B.P → They have low melting point and boiling point due to the weaker attractive forces.
(iii) Solubility → Covalent compounds are soluble in organic solvents like petrol, alcohol, etc., but insoluble in water.
(iv) Electrical conductivity → Poor conductors of electricity.
Example: NH₃ + H⁺ → (diagram showing donation of lone pair) → NH₄⁺ (Here NH₃ donates a lone pair and acts as the donor; H⁺ acts as the acceptor.)
This type of hybridization involves the intermixing of one s-orbital and one p-orbital to form two equivalent sp hybrid orbitals.
O + ∞ → sp (hybridization)
s¹ p¹
s¹
¹
Bond angle: 180° Forms a triple bond.
This type of hybridization involves the intermixing of one s-orbital and two p-orbitals to form three equivalent sp² hybrid orbitals.
O + ∞ + ∞ → sp² hybridization
s p p
s
Bond angle: 120° Forms a double bond.
This type of hybridization involves the intermixing of one s-orbital and three p-orbitals to form four sp³ hybrid orbitals.
O + ∞ + ∞ + ∞ → sp³ hybridization
s p p p
Forms a single bond.
The bond which binds metal atoms together is called a metallic bond.
When any beam of light falls on the surface of a metal, the free electrons in the metal begin to vibrate with the same frequency of light so the metal appears lustrous.
When electricity is passed through a metal, the free electrons begin to move from one end of the conductor to the other end due to potential difference. This movement of electrons causes electrical current.
Metals can be beaten into sheets — this property is called malleability. They can also be drawn into wires — this is called ductility. Metals exhibit these properties due to the non-directional nature of metallic bonds.
Metals have high tensile strength; i.e., metals can resist stretching without breaking.
CHAPTER - 4
It is a material which produces heat on combustion and can be used for any purpose.
A good fuel should have high calorific value — it should produce a large amount of heat.
A good fuel should produce minimum smoke, as smoke causes pollution and may contain poisonous gases.
It should be easily transported from one place to another.
It should be cheaper than other sources.
It should be easy to store and the cost of storage should be low.
It should be readily available in usable form.
It should have low or no moisture content. If moisture is present in fuel, the calorific value becomes very low and it produces maximum smoke.
The fuels which are solid at room temperature. Examples: wood, coal, lignite, etc.
The fuels which are liquid at room temperature. Examples: kerosene, petrol, oil, etc.
These are found in gaseous state. Examples: coal gas, natural gas, etc.
It is the amount of heat produced by complete combustion of unit mass of fuel in air.
The petroleum is refined by fractional distillation. The process by which petroleum is separated in various fractions is called refining of petroleum.
There are three steps in refining:
Petroleum contains emulsions. To break this emulsion, the crude oil is passed between two charged electrodes and water in the form of droplets comes out.
Sulphur is very undesirable in petroleum. So it is removed by heating petroleum with (CuO).
In this process, the crude oil is heated to 400°C in an iron retort. It contains a number of horizontal trays at short intervals. Each tray is provided with a chimney at different temperatures. At high temperature, fractions condense. After complete process, the residue left is in the form of asphalt or petroleum coke.
Producer gas is mainly a mixture of carbon monoxide and nitrogen (CO + N₂). It is manufactured by blowing a mixture of air and steam through a bed of red-hot coke or coal. The plant used for the manufacture of producer gas is called a gas producer. The producer is filled with coke and the mixture of air and steam is passed through it.
Oil gas is a mixture of different hydrocarbons. Oil gas is prepared by the thermal decomposition or cracking of kerosene oil; therefore it is known as oil gas.
The kerosene oil is poured slowly and continuously into a red-hot iron retort. When it is heated strongly, it gets converted into hydrocarbons:
CHAPTER - 5
Water is the most important and abundant gift of nature, which is present 75% on earth. There are many sources of water, which may be rain water, river water, well water, spring water, sea water.
The water which gives more lather with soap solution easily.
The water which does not give lather with soap solution.
The cause of hardness is due to the presence of calcium and magnesium.
The temporary hardness of water is due to the presence of bicarbonates of calcium or magnesium: Ca(HCO₃)₂, Mg(HCO₃)₂ It can be removed by boiling.
The permanent hardness of water is mainly due to the presence of dissolved chlorides and sulphates of calcium and magnesium: CaCl₂, MgCl₂, CaSO₄ and MgSO₄ It cannot be removed by boiling. It can be removed by many treatments.
On boiling, the bicarbonates of calcium and magnesium decompose and form carbonates which are insoluble. Then the water is filtered to remove insoluble carbonate and it becomes soft.
Reaction: Ca(HCO₃)₂ → (boil) → CaCO₃ + CO₂ + H₂O
Temporary hardness can be removed by adding calculated quantity of lime. When the soluble bicarbonates of calcium and magnesium are precipitated as insoluble carbonates, they are removed by filtration and water becomes soft.
Reaction: Mg(HCO₃)₂ + 2Ca(OH)₂ → Mg(OH)₂ + 2CaCO₃ + 2H₂O
In this method, washing soda (Na₂CO₃) is added to hard water and all the salts causing temporary as well as permanent hardness are precipitated as insoluble carbonates, which can be removed by filtration and water becomes soft.
Reaction: MgSO₄ + Na₂CO₃ → MgCO₃ + Na₂SO₄
Both lime (Ca(OH)₂) and soda (Na₂CO₃) are added. In this method, temporary and permanent hardness of water are removed. Ca(HCO₃)₂ and Mg(HCO₃)₂ are completely removed by lime. CaCl₂ and CaSO₄ are removed completely by soda. MgCl₂ and MgSO₄ are removed by using both soda and lime.
Reaction: MgSO₄ + Na₂CO₃ + Ca(OH)₂ → Mg(OH)₂ + CaCO₃ + Na₂SO₄
This is the modern method for removal of temporary as well as permanent hardness of water. Sodium zeolite is chemically hydrated sodium aluminium silicate having the formula: Na₂Z·Al₂Si₂O₈·XH₂O
It is capable of exchanging its sodium ions reversibly with hardness-producing ions (Ca²⁺, Mg²⁺) in water.
Includes diagram showing:
Sodium zeolite is placed with a bed of gravel and coarse sand over it in a suitable container. The hard water is allowed to pass through these layers. When calcium and magnesium ions present in hard water react with it, forming insoluble calcium and magnesium aluminium silicates which are retained in the filter bed and soft water is tapped out.
MgSO₄ + Na₂Z → MgZ + Na₂SO₄
Scale: A scale is a thick hard deposit on the inside of the boiler. Sludge: Mixture of CaCO₃ and Mg(OH)₂.
Priming: The bubbles present in water.
Disadvantages:
Equilibrium state: In any reaction when the reactant and product are present together in the reaction mixture. Neither the forward reaction nor the backward or reverse reaction is complete and it appears as if the reaction has stopped. It is known as equilibrium state.
aA + bB → Product Rate of reaction: r = k [A]ᵃ [B]ᵇ
aA + bB ⇌ cC + dD
K=K1K2=[C]c[D]d[A]a[B]bK = \frac{K_1}{K_2} = \frac{[C]^c [D]^d}{[A]^a [B]^b}K=K2K1=[A]a[B]b[C]c[D]d
Where K is called the equilibrium constant.
CHAPTER - 7
Metal → The element which can donate the electron and having the properties of lustre, ductile, malleable etc.
→ It is hard and brittle → Its melting point ranges between 1100°C to 1800°C → It does not rust easily → It cannot be welded easily → It is slightly ductile → It can be easily cast into mould of desired shape
It is the process of heating or cooling of solid state steel of controlled condition in such a way that its physical properties are changed without change in chemical properties. Various methods for the heat treatment of steel are:
(a) Low temperature annealing → In this process the steel is heated to below critical temperature and cooled slowly in a furnace. By this method the steel becomes ductile and decreases the hardness of steel.
(b) High temperature annealing → In this process the steel is heated to above higher critical temperature and then cooled slowly in a furnace. By this method the steel becomes softer, toughness and ductile.
Effect of silicon → Normally the silicon contents in cast iron varies b/w (2.5 to 3%). Silicon if present in smaller proportion (less than 2.5%) makes the metal soft and free from defect like blow holes and silicon if present in high proportion more than 2.5% then it forms iron silicate and causes the metal hard and brittle. Thus the proportion of Si should be kept low for big casting and higher for small casting.
CHAPTER - 8 ← Alloys →
Alloys → Alloy is the homogeneous mixture of two or more elements in which at least one is metal.
Necessity of making alloys:
(1) To increase hardness → Those elements which are generally soft are mixed with any hard metal to make it hard like copper is added in pure gold for making jewellery.
(2) To increase corrosion resistance of metals → These elements which are generally hard resistant of corrosion sometimes are added with non-corrosion materials to make it corrosion resistant.
(3) To modify colour → The elements are generally alloyed with other element to improve the colour.
(4) To improve malleability and ductility → The element having low malleability and ductility is make alloyed with any metal with good malleable and ductile. Like aluminium (Al + Cu).
(5) To modify chemical reaction → The chemical reactivity of a metal can be increased or decreased by making it alloy. For example chemical reactivity of sodium decreased by adding mercury.
(6) To lower melting and boiling point → The melting point of some alloys such as solder are lower than any of the constituent. This is alloying of metal makes them easily fusible. Solder for example an alloy of tin and lead has a melting point of 185°C and wood’s metal an alloy of Bi + Sn has melting point of only which is lower than its component.
← Classification of alloys →
The alloys may be classified into two types:
1. Ferrous alloys → The alloying which containing iron as one of the main component are known as ferrous alloys. Ex.: Steel
(a) Chromium steel → A small amount of chromium is added to the steel to make it corrosion resistant. This steel is used in making surgical instrument and cutlery instrument.
(b) Nickel steel → A small amount of nickel is added to steel to make it hard and brittle. The steel is used in making scientific instruments.
2. Non ferrous alloys → The alloys which do not contain iron as one of the main component. Ex. – brass, bronze etc…
(a) Brass → Brass is an alloy of copper and zinc. Ordinary brass is quite soft and contains 70–80% Cu and 30–20% Zn.
Properties → → It has high tensile strength. → It has low melting point. → It has low electrical conductivity. → It has more durability & machinability.
Uses → It is used for making utensils, cartridge cases, sheets, pipes, etc.
(b) Bronze → Bronze is an alloy of copper and tin. Cu (80–95%), Sn (2–5%)
Properties → → It is ductile. → It has high corrosion resistance. → It has a tough structure. → It can be readily casted and machined.
Uses → Used for making coins, medals, ornaments etc.
(c) Duralumin → It is an alloy of aluminium and copper, magnesium and manganese; also known as Dural. Al (95%), Cu (4%), Mg (0.5%), Mn (0.5%)
Properties → → It is light and tough.
→ It is a good conductor of heat and electricity. → It has good corrosion resistance. → It is highly ductile and highly malleable.
Uses → → Used for making aeroplane parts → Used for making automobile parts, utensils, cables, surgical instruments, space satellites, cookers etc.
(d) Gun Metal → Gun metal is composed of copper, tin and zinc. Cu (87%), Sn (10%), Zn (3%)
Properties → → It is generally hard, tough and strong. → It has good resistance to corrosion. → It has good shock resisting property.
Uses → Used for making gears for automobiles, pumps etc.
(Effect of carbon, nickel, chromium, Magnese)
Steel with small amount of alloying elements is known as alloy steel or special steel.) The alloying elements like nickel, chromium, manganese etc., though present in small amount, affect the physical properties of steel as follows:
Effect of Carbon → The carbon content plays a significant role to improve the useful character of steel. (i) Its tensile strength increases. (ii) The steel becomes harder and less ductile. (iii) Its weldability decreases. (iv) It becomes more wear resistant.
Effect of Chromium → (i) Addition of chromium to steel makes it hard and tough. (ii) Addition of chromium to steel increases its tensile strength. (iii) It increases impact resistance of steel. (iv) Presence of chromium decreases machinability of steel.
Effect of Nickel → A small content of nickel generally affects the properties of steel. → Presence of nickel increases toughness of steel. → It improves tensile strength of steel. → It increases ductility of steel. → It makes the steel heat and corrosion resistant.
Effect of Manganese → → Presence of manganese in steel increases strength and brittleness. → Steel containing manganese becomes hard and has high tensile strength. → Presence of manganese in steel increases shock and wear resistance.
Magnet → The element which can attract or repel any other substance in a certain area is called magnet.
It may be classified into three parts:
(i) Diamagnetic → The property of element by which it can repel other substance in a certain magnetic field. For ex → Cu, Zn, Bismuth.
(ii) Paramagnetic → The property of element by which it can attract in small attractive force in magnetic field. For ex → Aluminium.
(iii) Ferromagnetic → The property of element by which it can attract other substance with high electromagnetic force in certain magnetic field. For ex → Iron, Nickel.
Corrosion →
Corrosion → When a metal is affected by the substance present around it like moisture, humidity, acid and oxide called corrosion.
Types of corrosion →
(1) Dry corrosion (2) Wet corrosion
Dry corrosion → It is the type of corrosion in which metal is affected by the atmospheric gases like oxygen, carbon dioxide, sulphur dioxide etc.
→ Dry corrosion by oxygen → It is the type of corrosion in which metal is affected by oxygen only. This type of corrosion taken occur in presence of moisture is called oxidation corrosion. Ex → Na, K etc.
→ Dry corrosion by other gases → The corrosion when occurs due to other gases like SO₂, CO₂, H₂S etc (sulphur dioxide, carbon dioxide etc). The degree of affection is depend upon protective layer on its surface.
(2) Wet corrosion / electrochemical corrosion → It is the type of corrosion which takes place through ionic reaction in the moisture with a metal called electrochemical corrosion.
It occurs when a conducting material is kept in contact with any aqueous solution in presence of anode and cathode causing ionic reaction b/w metal and solution causes corrosion.
Electrochemical theory → This theory explains wet corrosion. It is based upon principle of that ‘when two different metal are placed in the same liquid in a aqueous soln then number of galvanic cell are set up due to electrochemical reaction.
Ex → Zn → Zn²⁺ + 2e⁻ (Oxidation) H₂O → H⁺ + OH⁻
The electrochemical corrosion depends upon nature of material when is placed in liquid. This type of corrosion is based upon the principle that when two different metals are placed in the same liquid in a aqueous solution.
Prevention of corrosion →
(1) By oiling and greasing → It is the process in which a layer of grease (oil) is treated on the surface of material. They protect metal with moisture & prevent from corrosion.
→ By painting → It is the process in which a layer of paint is coated on the surface of material. They protect metal from corrosion.
→ By galvanisation → It is the process in which a thin layer of zinc is coated on the surface of iron to prevent it from corrosion.
→ Metal spraying → It is the process in which a non-corroding surface on any material by spray guns. In this process the layer formed on the surface becomes non-porous.
→ Metal cladding → It is the process in which two metals are rolled by heavy rollers at high temperature and pressure. A thick homogeneous layer forms on surface of metal which is to be protected from corrosion.
→ Plastic coating → A plastic coating is effective in protecting the metal from corrosion. The surface of metal is dipped in molten or liquid solution of plastic (e.g. ethyl) where thick coating is formed on cooling.
Plastic → It is defined as the organic material of high molecular mass which can be moulded into any desired shape by using heat and pressure.
→ Lighter in weight → Easily moulding → Good thermal and electrical insulators → Corrosion resistance → Adhesiveness → Insect resistance → Good shock absorptivity → Good strength → Toughness → Low softening point → High refractive index → Transparency → Lower in cost
Polymers → Polymers are the high molecular mass substances formed by combination of a large number of simple molecules.
Natural polymers → The polymers which are found in nature. For ex: starch, cellulose, proteins etc.
Synthetic polymers → The polymers which are synthesised in the laboratory are known as synthetic polymers.
(1) Linear polymers → In this polymer the monomer units are linked together to form linear chain. These polymers have high density, high MP and high tensile strength. For ex: Polythene, nylon, PVC.
(2) Branched chain polymers → In these polymers, the monomers are held together to form long linear chain having branches or side chains at different lengths along the main chain. They have low MP, density and tensile strength. Ex: Polythene, starch, glycogen.
(3) Cross linked polymers → These polymers are formed from bi-functional or tri-functional monomers and the linear polymeric chain have strong covalent bonds called cross links.
(Diagram showing cross-linking)
Ex: Bakelite, melamine.
Thermoplastic
Thermosetting Plastic
Examples: Polythene, PVC, nylon-6, nylon-66.
Addition polymers are formed by direct repeated addition of monomer molecules possessing double or triple bond. It is called addition polymerisation.
Ex: PVC, natural rubber.
CH2 = CH2 → Polymerisation → { – CH2 – CH2 – }n
= CH2 → Polymerisation → { – CH2 – CH2 – }n
A polymer formed by the condensation of two or more monomers with the elimination of some simple molecule like water, HCl, is known as condensation polymerisation.
Ex: Terylene, bakelite, nylon-6, melamine.
Chemistry Important
Q1. Bohr’s theory of hydrogen atom. Q2. Quantum numbers, J.J. Thomson type. Q3. Hydrogen spectrum, Anderson principle. Q4. Modern periodic law and limitation of periodic table. Q5. Definition of atomic radius, ionization energy, electron negativity, ionic radius, and the variation in periodic table. Q6. Properties of p-block elements. Q7. Difference between ionic and covalent compounds. Q8. Hybridization. Q9. Conditions of ideal fuel. Q10. Method of fractional petroleum. Q11. Concept by Sorensen on pH scale(soil/gas unclear). Q12. Types of hardness. Q13. Zeolite method. Q14. Disadvantage of hardness in boiler. Q15. Law of control equilibrium. (crossed but listed) Q16. Paul explanation. Q17. Effect of phlogopore in cast iron. Q18. Necessity of making alloy. Q19. Explain Bragg’s theory and Davisson and Germer model. Q20. Electrical chemical theory. Q21. Prevention of corrosion. Q22. Advantages of plastic. Q23. Difference between addition and condensation polymerization. Q24. Thermoplastic and thermosetting plastics.