Tautomerism: It is a special type of functional isomerism in which a single compound exists in two readily inter convertible structures that differ markedly in the relative position of atleast one atomic nucleus, generally hydrogen. The two different structures are known as tautomers. ere are several types of tautomerism and the two important types are  dyad and triad systems.
(a) Dyad system: In this system hydrogen atom oscillates between two directly linked polyvalent atoms.
In this example hydrogen atom oscillates between carbon and nitrogen atom
\(\underset { (hydrogencyanide) }{ H } -C\equiv N\longleftrightarrow \underset { (hydrogenisocyanide }{ H } -N\overset { \rightarrow }{ = } C\)
(b) Triad system: In this 'system hydrogen atom oscillates between three polyvalent atoms. It involves 1,3 migration of hydrogen atom from one polyvalent atom to other within the molecule. e most important type of triad system is keto-enol tautomerism and the two groups of tautomers are ketoform and enol-form. The polyvalent atoms involved are one oxygen and two carbon atoms. Enolisation is a process in which keto-form is converted to enol form. Both tautomeric forms are not equally stable. The less stable form is known as lable form
Example:

(c) Ring chain isomerism: In this type of isomerism, compounds having same molecular formula but differ in terms of bonding of carbon atom to form open chain and cyclic structures for eg:

Elimination reactions may proceed through two different mechanisms namely E₁ and E₂

(i) The rate of E₂ reaction depends on the concentration of alkyl halide and base Rate = k [alkyl halide] [base]
(ii) It is therefore, a second order reaction. Generally primary alkyl halide undergoes this reaction in the presence of alcoholic KOH. It is a one step process in which the abstraction of the proton from the . p carbon and expulsion of halide from the a carbon occur simultaneously. The mechanism is shown below.


(iii) Generally, tertiary alkyl halide which undergoes elimination reaction by this mechanism in the presence of alcoholic KOH. It follows first order kinetics. Let us. consider the following elimination reaction.
Step - 1: Heterolytic fission to yield a carbocation

Step - 2 Elimination of a proton from the \(\beta\)- carbon to produce an alkene.

Given data:
[A] = [B] = [C]= [D] =1 M
K_c = 100
[D]_eq = ?
Solution:
Let x be the no moles of reactants reacted

	A	B	C	D
Initial concentration	1	1	1	1
At equilibrium (as per reaction stoichiometry)	1-x	1-x	1-x	1-x

\(K_c={[C][D]\over [A][B]}\)
\(100={(1+x)(1+x)\over (1-x)(1-x)}\)
\(\sqrt{100}=\sqrt{{(1+x)(1+x)\over (1-x)(1-x)}}\)
\(10={1+x\over 1-x}\)
10(1 - x) = 1 + x
10 - 10x - 1 - x = 0
9 - 11x = 0
11x = 9
\(x={9\over 11}=0.818\)
[D]eq = 1+x = 1 + 0.818 = 1.818M.

Step 2. P + 5HNO₃ \(\rightarrow\)H₃PO₄ +5 NO₂ + H₂O

(i) An element (A) belonging to group number 1 and period number 3 is sodium (A).
(ii) Sodium reacts with hydrogen to form sodium hydride (B)
2Na + H2 ➝ 2NaH
   (A)  (B)       (C)
(iii) Sodium reacts with water to form sodium hydroxide (C).
2Na + 2H₂O ➝ 2NaOH + H₂
  (A)                    (C)

A	Na	Sodium
B	NaH	Sodium hydride
C	NaOH	Sodium hydroxide

n = 5; V = 2 Iitre;T= 27 + 273 = 300 K
\(P=\frac { nRT }{ V } [\because PV=nRT]\)
\(P=\frac { 5\times 8.314\times 300 }{ 2 } =62.355\quad bar\)
\(\therefore\) The pressure of CI₂ gas will be 62.355 bar.

(i) Free energy is defined as G = H - TS. 'G' is a state function.
(ii) G- Extensive property; ΔG - intensive property. When mass remains constant between initial and final states of system.
(iii) 'G' has a single value for the thermodynamic state of the system.
(iv) G and ΔG values correspond to the system only.

Process	Spontaneous	Equilibrium	Non-Spontaneous
ΔG	-Ve	Zero	+Ve

(v) Gibbs free energy and the net work done by the system:
For any system at constant pressure and temperature
ΔG = ΔH - TΔS .....(1)
We know that,
ΔH = ΔU + PΔV
ΔG =ΔU + PΔV-TΔS
from first law of thermodynamics
ΔU = q +w
from second law of thermodynamics
Δ S=\(\frac{q}{T}\) Δ G=q+w+PΔ V-T\((\frac{q}{T}) \)
Δ G = w+PΔV
-ΔG = -w - PΔV ......(2)
But -PΔV represents the work done due to expansion against a constant external pressure.

(i) Magnesium and calcium also play a vital role in biological functions. A typical adult human body contains about 25 g of magnesium and 1200 g of calcium. Magnesium plays an important· role in many biochemical reactions catalysed by enzymes. It is the co-factor of all enzymes that utilize ATP in phosphate transfer and energy release. It is also essential for DNA synthesis and is responsible for the stability and proper functioning of DNA.It is also used for balancing electrolytes in our body. Deficiency of magnesium results into convulsion and neuromuscular irritation.
(ii) Calcium is a major component of bones and teeth. It is also present in blood and its concentration is maintained by hormones (calcitonin and parathyroid hormone). Deficiency of calcium in blood causes it to take longer time to clot. It is also important for muscle contraction.
(iii) The main pigment that is responsible for photosynthesis, chlorophyll, contains magnesium which plays an important role in photosynthesis.

The electronic configuration of Sodium (Z = 11) Is²2s²2p⁶3s¹.
Magnesium (Z = 12) 1s²2s²2p⁶3s²
Magnesium atom has a smaller radius and higher nuclear charge than a sodium atom, thus more energy will be required to remove the electron from the same orbital (3s), making the first ionisation energy of magnesium higher than that of sodium.
However, the second ionization enthalpy of sodium is higher than that of magnesium. This is because after losing 1 electron, sodium attains the stable noble gas configuration of neon (1s²2s²2p⁶). On the other hand, magnesium, after losing 1 electron still has one electron in the 3s-orbital(1s²2s²2p⁶3s¹). In order to attain the stable noble gas configuration, Thus, the energy required to remove the second electron in case of sodium is much higher than that required in case of magnesium. Hence, the second ionization enthalpy of sodium is higher than that of magnesium.

'The bond angle of HSH is 92.2° and that of H₂0 is 104.5°
The higher bond angle in water molecule is due to the higher electronegativity of oxygen (in H₂0) than sulphur (in H₂S).

When the π electron is transferred toward the attacking reagent, it is called +E (positive electromeric) effect.

The addition of H⁺ to alkene as shown above is an example of +E effect.
When the electron is transfered away from the attacking reagent, it is called, -E (negative electromeric) effect.

The attack of CN^- on a carbonyl carbon, as shown above, is an example of -E effect

S.No	Classical somg (london smog)	Photochemical smog (Los Angels smog)
1	It was first observed in London in Dec. 1952	It was first observed in Los Angels in 1950.
2	It occurs in cool, humid climate	It occurs in warm, dry and sunn climate
3	It consists of coal smoke and fog	It is formed by the combination of smoke dust and fog with air pollutants like N2 and hydrocarbons in presence of light.
4	It generally occurs in the morning and becomes worse when the sunshines	It forms when the sunshines and becomes worse in the afternoon.
5	This is mainly due to the induced oxidation of SO2 to SO3, which reacts with water yielding sulphuric acid aerosol.	This is mainly due to the induced oxidation of N2 to NO, NO2 and [O] + O2 to O3 NO and O3 are strong oxidising agents and can react with unburnt hydrocarbons in polluted air to form HCHO, Acrolein and PAN.
6	Chemically it is reducing in nature because of high concentration of SO2.	Chemically it is oxidising in nature because of high concentrations of oxidising agents like NO2 and O2
7	It is called reducing smog	It is called oxidising smog
8	Responsible for acid rain, causes poor visibility, affects air and road transport and causes bronchial irritation.	Causes irritation to nose, throat, eyes, skin and lungs, increases asthma, causes chest pain, uncomfortable breathing, PAN attacks young leaves, causes corrosion of metals, stones painted surfaces, etc.,

Alcoholscanbeconvertedintohaloalkenesbyreactingit withanyoneofthefollowingreagent
1.hydrogen halide
2. Phosphorous halides
3. Thionyl chloride
a) Reaction with hydrogen halide:
\(\underset { Ethanol }{ { CH }_{ 3 }{ CH }_{ 2 }OH+HCl } \overset { Anhydrous\\ ZN{ Cl }_{ 2 } }{ \underset { \triangle }{ \longrightarrow } } \underset { Chloroethane }{ { CH }_{ 3 }{ CH }_{ 2 }Cl+{ H }_{ 2 }O } \)
Mixture of con.HCI and anhydrous ZnCl₂ is called Lucas reagent
b) Reaction with phosphorous halides :
Alcohols react with PX₅ or PX₃ to form haloalkane. PBr₃ and PI₃ are usually generated in situ (produced in the reaction mixture) by the reaction of red phosphorus with bromine and iodine, respectively.

c)Reaction with thionyl chloride :

This reaction is known as Darzen's halogenation

(i) Hydrogen, nitrogen, oxygen, fluorine and chlorine exist as gaseous diatomic molecules.
(ii) Another form of oxygen namely ozone triatomic molecule exists as a gas at room temperature.
(iii) Noble gases namely helium, neon, argon, krypton, xenon and radon are monoatomic gases.

Ionization enthalpy, among other things, depends upon the electronic configuration (number of electrons) and nuclear charge (number of protons). Since isotopes of an element have the same electronic configuration and same nuclear charge, they have same ionization enthalpy.

2 mole of H₂ react with 1mole of O₂.
1.5 mole of H react with 0.75 mole of O₂.
Excess O₂ = 0.9062 - 0.75 = 0.1562 mol.

Heavy water is toxic when taken in large quantities. Heavy water is not radioactive. The deuterium in it is stable; it does not decay. Nobody will be in danger at all from radiation. It is heavier than plain water. D₂O performs little different from H₂O in chemical reactions. One has to drink a lot of D₂O to kill him.

Orbital	n	1	Radial node n-1-1	Angular node 1
2s	2	0	1	0
4p	4	1	2	1
5d	5	2	2	2
4f	4	3	0	3

The structure of benzene is best described in terms of the molecular orbital theory. All the six carbon atoms of benzene are sp² hybridized. Six sp² hybrid orbitals of carbon linearly overlap with six one is orbitals of hydrogen atoms to form six C - H sigma bonds. Overlap between the remaining Sp² hybrid orbitals of carbon forms six C-C sigma bonds

All the bonds in benzene lie in one plane with bond angle 120°. Each carbon atom in benzene possess an un hybridized p-orbital containing one electron. The lateral overlap of their p-orbital produces 3 \(\pi\)-bond The six electrons of the p-orbitals cover all the six carbon atoms and are said to be delocalised. Due to delocalization, strong -bond is formed which makes the molecule stable. Hence unlike alkenes and alkynes benzene undergoes substitution reactions rather addition reactions under normal conditions.

Distillation	DistillationUnder ReducedPressure	Steam Distillation
It involves conversion of liquidinto       vapourbyheating followed by the condensation of vapours by cooling	It is applicable for purification of liquids with high boiling points and those which decompose at a temperature lower than its boiling point.	It is used for separation and purification of organic compounds from non - volatile impurities.
It is suitable for liquids which possess stable boiling points and contain non - volatile impurities.	A liquid boils when its vapour pressure becomes equal to the external pressure, obviously the liquid will boil at a lower temperature, if  the pressure on it is reduced. Since the liquid boils at a temperature below its boiling point it does not undergo decomposition.	This method is applicable to all those compounds which are volatile in steam, insoluble in water, possess a high vapour pressure and contain non -volatile impurities.

Pesticides are the chemicals that are used to kill or stop the growth of unwanted organisms. But these pesticides can affect the health of human beings. These are further classified as
a. Insecticides:
Insecticides like DDT ,BHC ,aldrin etc. can stay in soil for long period of time and are absorbed by soil . Th.y contaminate root crops like carrot, raddish, etc.
b. Fungicide :
Organo mercury compeunds are used as most common fungicide. They dissociate in soil to produce mercury which is highly toxic.
c. Herbicides :
Herbicides are the chemical compounds used to control unwanted plants. They are otherwise known as weed killers. Example sodium chlorate (NaClO₃) and sodium arsenite (Na₃ As O₃). Most of the herbicides are toxic to mammals.

The first six members of nitro alkanes are
(i) CH₂-NO₂ - Nitromethane
(ii) CH₂-CH₂-NO₂ - Nitroethane
(iii) CH₃-CH₂-CH₂-NO₂ - 1- nitropropane'
(iv) CH₃-CH₂-CH₂-CH₂-NO₂ - 1- nitrobutane
(v) CH₃-CH₂-CH₂-CH₂-CH₂-NO₂ - 1- nitropentane
(vi) CH₂-CH₂-CH₂-CH₂-CH₂-CH₂ - NO₂ - 1- nitrohexane

\({\Delta P\over P_A^o}={W_B\times M_A\over M_B\times W_A}\)
In a 2 % solution weight of the solute is 2g and solvent is 98g
ΔP = P_A - P_solution = 1.013 - 1.004 bar = 0.009 bar
\(M_B={P_A^o\times W_B\times M_A\over \Delta P\times W_A}\)
M_B = 2 x 18 x 1.013/(98 x 0.009)
= 41.3 g mol^-1.

\(\Delta n_{g}=\sum n p_{(g)}-\sum n R_{(g)}\)
As \(\Delta n_{p}(g)\) is greater \(\Delta n_{g}=+v e\)
\( \therefore K_{p}=K_{c}(R T)^{+v e} \)
\(\therefore K_{p}>K_{c} \)
So K is smaller than K_p.

(i) The number of electrons increases by the same number as the increase in the atomic number.
(ii) As the number of electrons increases, the electronic structure of the atom changes.
(iii) Electrons in the outermost shell of an atom (valence shell electrons) determine the chemical properties of the elements.

For one mole of an ideal gas, we have
\({ C }_{ v }=\frac { dU }{ dT } \)
dU=C_v dT
For a finite change, we have
\(\Delta U={ C }_{ v }\Delta T\)
\(\Delta U={ C }_{ v }({ T }_{ 2 }-{ T }_{ 1 })\)
and for n moles of an ideal gas we get \(\Delta U=n{ C }_{ v }({ T }_{ 2 }-{ T }_{ 1 })\)   .....(1)
Similarly for n moles of an ideal gas we get \(\Delta H=n{ C }_{ p }({ T }_{ 2 }-{ T }_{ 1 })....(2)\)

The passenger in a moving bus falls in the forward direction, when brakes are applied suddenly is in accordance with Newton's first law of motion.
When breaks are applied, the automobile comes to rest but the passenger due to inertia of motion tend to continue to move in forward direction hence fall forward.
The movement of helium balloon in the opposite direction is due to the difference in the density of surrounding air. When the car stops suddenly, the air moves forward due to inertia of motion.
As a result the air in the front of the car is more dense that at the rear of the car creating more pressure on the front side of the balloon. This causes the balloon move towards the rear of the car where air is less dense.
The body is at rest but the car is forward motion, due to inertia the passengers are pushed toward the front of the car on forward acceleration.

1) The unit of molecular mass is atomic mass unit [amu]. The unit of molar mass is gram per mole.
2) Molecular mass is the mass of one molecule while molar mass is the mass of one mole of molecules (6.022 x 10²³)
(i) Molecular mass of CO₂ = 1(C) + 2(0) = 12 + 32 = 44 amu
or 7.304 x 10^-23 g
(ii) Molar mass of CO₂ = 44 g mol^-1.

iv) (A) is correct but( R) is not correct