The idea of oxidation number has been invariably applied to define oxidation, reduction, oxidising agent (oxidant), reducing agent (reductant) and the redox reaction. To summarise, we may say that: Oxidation: An increase in the oxidation number of the element in the given substance. Reduction: A decrease in the oxidation number of the element in the given substance. Oxidising agent: A reagent which can increase the oxidation number of an element in a given substance. These reagents are called as oxidants also. Reducing agent: A reagent which lowers the oxidation number of an element in a given substance. These reagents are also called as reductants. Redox reactions: Reactions which involve change in oxidation number of the interacting species. Types of Redox Reactions 1.) Combination reactions -A combination reaction may be denoted in the manner: A + B → C Either A and B or both A and B must be in the elemental form for such a reaction to be a redox reaction. All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen, are redox reactions. Some important examples of this category are: 2.) Decomposition reactions- Decomposition reactions are the opposite of combination reactions. Precisely, a decomposition reaction leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state. Examples of this class of reactions are: It may carefully be noted that there is no change in the oxidation number of hydrogen in methane under combination reactions and that of potassium in potassium chlorate in reaction. This may also be noted here that all decomposition reactions are not redox reactions. For example, decomposition of calcium carbonate is not a redox reaction. 3.) Displacement reactions- In a displacement reaction, an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element. It may be denoted as: X + YZ → XZ + Y Displacement reactions fit into two categories: metal displacement and non-metal displacement. (a) Metal displacement: A metal in a compound can be displaced by another metal in the uncombined state. Metal displacement reactions find many applications in metallurgical processes in which pure metals are obtained from their compounds in ores. (b) Non-metal displacement: The non-metal displacement redox reactions include hydrogen displacement and a rarely occurring reaction involving oxygen displacement. All alkali metals and some alkaline earth metals (Ca, Sr, and Ba) which are very good reductants, will displace hydrogen from cold water. Many metals, including those which do not react with cold water, are capable of displacing hydrogen from acids. Dihydrogen from acids may even be produced by such metals which do not react with steam. Cadmium and tin are the examples of such metals. 4.) Disproportionation reactions – Disproportionation reactions are a special type of redox reactions. In a disproportionation reaction an element in one oxidation state is simultaneously oxidised and reduced. One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least three oxidation states. The element in the form of reacting substance is in the intermediate oxidation state; and both higher and lower oxidation states of that element are formed in the reaction. The decomposition of hydrogen peroxide is a familiar example of the reaction, where oxygen experiences disproportionation. Here the oxygen of peroxide, which is present in –1 state, is converted to zero oxidation state in O2 and decreases to –2 oxidation state in H_2O. 1. In … an ion (or an atom) in a compound is replaced by an ion (or an atom) of another element. 1. displacement reaction 2. decomposition reaction 3. disproportionation reaction 4. combination reaction 2. leads to the breakdown of a compound into two or more components at least one of which must be in the elemental state. 1. displacement reaction 2. decomposition reaction 3. disproportionation reaction 4. combination reaction 3. In …. an element in one oxidation state is simultaneously oxidised and reduced. 1. displacement reaction 2. decomposition reaction 3. disproportionation reaction 4. combination reaction 4. Reactions which involve change in oxidation number of the interacting species… 1. Exothermic reaction 2. Endothermic reaction 3. Neutralization reaction 4. Redox reaction 5. One of the reacting substances in a disproportionation reaction always contains an element that can exist in at least … oxidation states. 1. 1 2. 2 3. 3 4. 4

1. (a) displacement reaction 2. (b) decomposition reaction 3. (c) disproportionation reaction 4. (d) Redox reaction 5. (c) 3

The idea of oxidation number has been invariably applied to defin…

IUPAC (International Union of Pure and Applied Chemistry) system of nomenclature. Common names are useful and in many cases indispensable, particularly when the alternative systematic names are lengthy and complicated. A systematic name of an organic compound is generally derived by identifying the parent hydrocarbon and the functional group(s) attached to it. By using prefixes and suffixes, the parent name can be modified to obtain the actual name. In a branched-chain compound, small chains of carbon atoms are attached at one or more carbon atoms of the parent chain. The small carbon chains (branches) are called alkyl groups. An alkyl group is derived from a saturated hydrocarbon by removing a hydrogen atom from carbon. Abbreviations are used for some alkyl groups. For example, methyl is abbreviated as Me, ethyl as Et, propyl as Pr and butyl as Bu.

1. Draw the structure of 3-Ethyl-4,4-dimethylheptane. (1)
2. How is the numbering in branched chain hydrocarbon done?
3. Derive the structure of 2-Chlorohexane. (2)
OR
Why $CH _4$ after becoming- $CH _3$ called a methyl group? (2)

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Read the passage given below and answer the following questions from 1 to 5 .
After having some idea about the terms atomsand molecules, it is appropriate here tounderstand what do we mean by atomic andmolecular masses. One atomicmass unit is defined as a mass exactly equal to one-twelfth of the mass of one carbon -12 atom.Molecular mass is the sum of atomic masses of the elements present in a molecule. It is obtained by multiplying the atomic mass of each element by the number of its atoms and adding them together. Some substances, such as sodium chloride, do not contain discrete molecules as their constituent units. In such compounds, positive (sodium ion) and negative (chloride ion) entities are arranged in a three dimensional structure. The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly $6.02214076 \times 10^{23}$ elementary entities. This number is the fixed numerical value of the Avogadro constant, $N _{ A }$, when expressed in the unit mol-1 and is called the Avogadro number. The amount of substance, symbol $n$, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles. It may be emphasised that the mole of a substance always contains the same number of entities, no matter what the substance may be. In order to determine this number precisely, the mass of a carbon-12 atom was determined by a mass spectrometer and found to be equal to $1.992648 \times 10^{-23} g$. Knowing that one mole of carbon weighs 12 g , the number of atoms in it is equal to: $12 g / mol C -12$.
$1.992648 \times 10^{23} g / C -12$ atom. $=6.0221367 \times 10^{23}$ atoms $/ mol$.
The mass of one mole of a substance in grams is called its molar mass. the molar mass in grams is numerically equal to atomic molecular/formula mass in u.An empirical formula represents the simplestwhole number ratio of various atoms present ina compound, whereas, the molecular formulashows the exact number of different types ofatoms present in a molecule of a compound. If the mass per cent of variouselements present in a compound is known, its empiricalformula can be determined. Molecular formulacan further be obtained if the molar mass isknown.Many a time, reactions are carried out with the Amounts of reactants that are different than The amounts as required by a balanced chemical reaction. In such situations, one Reactant is in more amount than the amount required by balanced chemical reaction. The reactant which is present in the least amount Many a time, reactions are carried out with the amounts of reactants that are different than the amounts as required by a balanced chemical reaction. In such situations, one reactant is in more amount than the amount required by balanced chemical reaction. The reactant which is present in the least amount gets consumed after sometime and after that further reaction does not take place whatever be the amount of the other reactant. Hence, the reactant, which gets consumed first, limits the amount of product formed and is, therefore, called the limiting reagent.
i. One atomic mass unit (amu) is defined as a mass exactly equal to one-twelfth of the mass of one ...atom.

One atomic mass unit (amu) is defined as a mass exactly equal to one-twelfth of the mass of one …atom.

Hydrogen $– 1$
Carbon $– 12$
Oxygen $-12$
Chlorine $– 35$

The mass of one mole of a substance in grams is called its..

Atomic mass
Molecular Weight
Molecular mass
Molar mass.

… is the sum of atomic massesof the elements present in a molecule.

Atomic mass
Molecular Weight
Molecular mass
Molar mass.

One mole contains exactly …elementary entities.

$02214076 \times 10^{21}$
$02214076 \times 10^{22}$
$6.02214076 \times 10^{23}$
$02214076 \times 10^{24}$

For which of the following compound , formula mass is preferred instead of molecular mass?

$NaCl$
$C2H6$
$N2$
$H2O$

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The molecular orbital theory is based on the principle of a linear combination of atomic orbitals. According to this approach when atomic orbitals of the atoms come closer, they undergo constructive interference as well as destructive interference giving molecular orbitals, i.e., two atomic orbitals overlap to form two molecular orbitals, one of which lies at a lower energy level (bonding molecular orbital). Each molecular orbital can hold one or two electrons in accordance with Pauli's exclusion principle and Hund's rule of maximum multiplicity. For molecules up to $N _2$, the order of filling of orbitals is:

Bond order $=\frac{1}{2}$ [bonding electrons - antibonding electrons]
Bond order gives the following information:
i. If bond order is greater than zero, the molecule/ion exists otherwise not.
ii. Higher the bond order, higher is the bond dissociation energy.
iii. Higher the bond order, greater is the bond stability.
iv. Higher the bond order, shorter is the bond length.

1. Arrange the following negative stabilities of $CN , CN ^{+}$and $CN ^{-}$in increasing order of bond.
2. The molecular orbital theory is preferred over valence bond theory. Why?
3. Ethyne is acidic in nature in comparison to ethene and ethane. Why is it so?
OR
Bonding molecular orbital is lowered by a greater amount of energy than the amount by which antibonding molecular orbital is raised. Is this statement correct?

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Read the passage given below and answer the following questions from $1$ to $5$.
The term ‘hydrocarbon’ is self-explanatory which means compounds of carbon and hydrogen only. Hydrocarbons play a key role in our daily life. You must be familiar with the terms ‘LPG’ and ‘CNG’ used as fuels. LPG is the abbreviated form of liquified petroleum gas whereas CNG stands for compressed natural gas. Another term ‘LNG’ (liquified natural gas) is also in news these days. This is also a fuel and is obtained by liquifaction of natural gas. Petrol, diesel and kerosene oil are obtained by the fractional distillation of petroleum found under the earth’s crust. Coal gas is obtained by the destructive distillation of coal. Natural gas is found in upper strata during drilling of oil wells. The gas after compression is known as compressed natural gas. LPG is used as a domestic fuel with the least pollution. Kerosene oil is also used as a domestic fuel but it causes some pollution. Automobiles need fuels like petrol, diesel and CNG. Petrol and CNG operated automobiles cause less pollution. All these fuels contain mixture of hydrocarbons, which are sources of energy. Hydrocarbons are also used for the manufacture of polymers like polythene, polypropene, polystyrene etc. Higher hydrocarbons are used as solvents for paints. They are also used as the starting materials for manufacture of many dyes and drugs. Thus, you can well understand the importance of hydrocarbons in your daily life. In this unit, you will learn more about hydrocarbons.
Classification Hydrocarbons are of different types. Depending upon the types of carbon-carbon bonds present, they can be classified into three main categories – (i) saturated
(ii) unsaturated and
(iii) aromatic hydrocarbons. Saturated hydrocarbons contain carbon-carbon and carbon-hydrogen single bonds. If different carbon atoms are joined together to form open chain of carbon atoms with single bonds, they are termed as alkanes. On the other hand, if carbon atoms form a closed chain or a ring, they are termed as cycloalkanes. Unsaturated hydrocarbons contain carbon-carbon multiple bonds – double bonds, triple bonds or both. Aromatic hydrocarbons are a special type of cyclic compounds. You can construct a large number of models of such molecules of both types (open chain and close chain) keeping in mind that carbon is tetravalent and hydrogen is monovalent. For making models of alkanes, you can use toothpicks for bonds and plasticine balls for atoms. For alkenes, alkynes and aromatic hydrocarbons, spring models can be constructed.
Alkanes As already mentioned, alkanes are saturated open chain hydrocarbons containing carbon – carbon single bonds. Methane $(CH_4)$ is the first member of this family. Methane is a gas found in coal mines and marshy places. If replace one hydrogen atom of methane by carbon and join the required number of hydrogens to satisfy the tetravalence of the other carbon atom,it get $C_2H_6$. This hydrocarbon with molecular formula $C_2H_6$ is known as ethane. Thus it can consider $C_2H_6$ as derived from $CH_4$ by replacing one hydrogen atom by $-CH_3$ group. Go on constructing alkanes by doing this theoretical exercise i.e., replacing hydrogen atom by $–CH_3$ group. The next molecules will be $C_3H_8, C_4H_{10} …$

These hydrocarbons are inert under normal conditions as they do not react with acids, bases and other reagents. Hence, they were earlier known as paraffins (latin: parum, little; affinis, affinity). the general formula for alkanes is $C_nH_2n + 2$. It represents any particular homologue when n is given appropriate value. methane has a tetrahedral structure, in which carbon atom lies at the centre and the four hydrogen atoms lie at the four corners of a regular tetrahedron. All H-C-H bond angles are of $109.5^\circ$ .
In alkanes, tetrahedra are joined together in which C-C and C-H bond lengths are 154 pm and 112 pm respectively. We have already read that C–C and C–H $\sigma$ bonds are formed by head-on overlapping of sp 3 hybrid orbitals of carbon and 1s orbitals of hydrogen atoms.
Difference in properties is due to difference in their structures, they are known as structural isomers. structural isomers which differ in chain of carbon atoms are known as chain isomers.
Preparation- Petroleum and natural gas are the main sources of alkanes. However, alkanes can be prepared by following methods:

1) From unsaturated hydrocarbons Dihydrogen gas adds to alkenes and alkynes in the presence of finely divided catalysts like platinum, palladium or nickel to form alkanes. This process is called hydrogenation. These metals adsorb dihydrogen gas on their surfaces and activate the hydrogen – hydrogen bond. Platinum and palladium catalyse the reaction at room temperature but relatively higher temperature and pressure are required with nickel catalysts.
2) From alkyl halides
i) Alkyl halides (except fluorides) on reduction with zinc and dilute hydrochloric acid give alkanes.

ii) Alkyl halides on treatment with sodium metal in dry ethereal (free from moisture) solution give higher alkanes. This reaction is known as Wurtz reaction and is used for the preparation of higher alkanes containing even number of carbon atoms.

Which of the following catalyst is used for hydrogenation…

platinum
palladium
nickel
All the above

LPG stands for ….

Liquid Pressure Gas
Liquefied Petroleum Gas
Liquid Platinum Gas
Liquid Processed Gas

Difference in properties is due to difference in their structures, they are known as …. isomers.

Functional
Positional
Structural
Chain

Structural isomers which differ in chain of carbon atoms are known as… isomers.

Functional
Positional
Structural
Chain

CNG Stands for ..

Compressed Natural Gas
Condensed Natural Gas
Compressed Neutral Gas
Compressed Neutral Gallium

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Read the passage given below and answer the following questions from 1 to 5 .
Group 14 elements: the carbon family-Carbon, silicon, germanium, tin lead and Flerovium are the members of group 14. Carbon Is the seventeenth most abundant element by Mass in the earth's crust. It is widely Distributed in nature in free as well as in the Combined state. In elemental state it is available As coal, graphite and diamond; however, in Combined state it is present as metal Carbonates, hydrocarbons and carbon dioxide Gas ( $0.03 \%$ ) in air. One can emphatically say That carbon is the most versatile element in the World. Its combination with other elements Such as dihydrogen, dioxygen, chlorine and Sulphur provides an astonishing array of Materials ranging from living tissues to drugs And plastics.
The valence shell electronic configuration of These elements is $ns ^2 np ^2$. The inner core of the Electronic configuration of elements in this Group also differs.
Covalent Radius There is a considerable increase in covalent Radius from C to Si, thereafter from Si to Pb a Small increase in radius is observed. This is Due to the presence of completely filled d and f Orbitals in heavier members. Ionization Enthalpy The first ionization enthalpy of group 14 Members is higher than the corresponding Members of group 13. The influence of inner Core electrons is visible here also. In general the lonisation enthalpy decreases down the group. Small decrease in $\Delta iH$ from Si to Ge to Sn and Slight increase in $\Delta i H$ from Sn to Pb is the Consequence of poor shielding effect of Intervening $d$ and $f$ orbitals and increase in size Of the atom. Electronegativity Due to small size, the elements of this group Are slightly more electronegative than group 13 elements. The electronegativity values for Elements from Si to Pb are almost the same.
Physical Properties All members of group14 are solids. Carbon and Silicon are non-metals, germanium is a metalloid, Whereas tin and lead are soft metals with low Melting points. Melting points and boiling points Of group 14 elements are much higher than those Of corresponding elements of group 13.
(i) Reactivity towards oxygen All members when heated in oxygen form Oxides. There are mainly two types of oxides, i.e., monoxide and dioxide of formula MO and $MO _2$ respectively. SiO only exists at high Temperature. Oxides in higher oxidation states Of elements are generally more acidic than Those in lower oxidation states. The dioxides $CO _2$, SiO 2 and $GeO _2$ are acidic, whereas $SnO _2$ and $PbO _2$ are amphoteric in nature. Among monoxides, CO is neutral, GeO is Distinctly acidic whereas SnO and PbO are Amphoteric.
(ii) Reactivity towards water Carbon, silicon and germanium are not Affected by water. Tin decomposes steam to Form dioxide and dihydrogen gas.
$Sn+2 H_2 O \rightarrow SnO_2+2 H_2$
Lead is unaffected by water, probably Because of a protective oxide film formation.
(iii) Reactivity towards halogen These elements can form halides of formula $M X_2$ and $M X_4$ (where $\left.X=F, C l, B r, I\right)$. Except Carbon, all other members react directly with Halogen under suitable condition to make Halides. Most of the $MX _4$ are covalent in nature. The central metal atom in these halides Undergoes $sp ^3$ hybridisation and the molecule Is tetrahedral in shape. Exceptions are $SnF _4$ And $PbF _4$, which are ionic in nature.
Carbon atoms have the tendency to link With one another through covalent bonds to Form chains and rings. This property is called Catenation. This is because C-C bonds are Very strong. Down the group the size increases and electronegativity decreases, and, thereby, Tendency to show catenation decreases. This Can be clearly seen from bond enthalpies Values. The order of catenation is $C > Si > Ge \approx Sn$. Lead does not show catenation.

Which of the following is not the member of group 14 ?

boron
silicon
germanium
tin

… does not show catenation.

Carbon
Lead
Silicon
Germanium

Which of following elements are affected by water ?

carbon
silicon
germanium
All the above

The valence shell electronic configuration of Group 14 elements is …

$ns^2np^4$
$ns^2np^5$
$ns^2np^2$
$ns^2np^3$

Half-life of $^{14}C$ is … years.

6570
4570
5770
1970

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Read the passage given below and answer the following questions from (i) to (v).

The attractive force which holds variousconstituents (atoms, ions, etc.) together in differentchemical species is called a chemical bond. In order to explain the formation of chemicalbond in terms of electrons, a number ofattempts were made, but it was only in 1916 when Kössel and Lewis succeededindependently in giving a satisfactoryexplanation. They were the first to providesome logical explanation of valence which wasbased on the inertness of noble gases. Lewis postulated that atoms achieve thestable octet when they are linked bychemical bonds. In the formation of amolecule, only the outer shell electrons takepart in chemical combination and they areknown as valence electrons. The inner shellelectrons are well protected and are generallynot involved in the combination process.G.N. Lewis, an American chemist introducedsimple notations to represent valenceelectrons in an atom. These notations arecalled Lewis symbols. For example, the Lewissymbols for the elements of second period areas under:
The bond formed, as a result of theelectrostatic attraction between thepositive and negative ions was termed as the electrovalent bond. The electrovalenceis thus equal to the number of unitcharge(s) on the ion.
Kössel and Lewis in 1916 developed animportant theory of chemical combinationbetween atoms known as electronic theoryof chemical bonding. According to this,atoms can combine either by transfer ofvalence electrons from one atom to another(gaining or losing) or by sharing of valenceelectrons in order to have an octet in theirvalence shells. This is known as octet rule. when two atoms share oneelectron pair they are said to be joined bya single covalent bond. In many compoundswe have multiple bonds between atoms. Theformation of multiple bonds envisagessharing of more than one electron pairbetween two atoms. If two atoms share twopairs of electrons, the covalent bondbetween them is called a double bond. Forexample, in the carbon dioxide molecule, wehave two double bonds between the carbonand oxygen atoms. Similarly in ethenemolecule the two carbon atoms are joined bya double bond. The Lewis dot structures provide a pictureof bonding in molecules and ions in termsof the shared pairs of electrons and theoctet rule. The Lewis dotstructures can be written by adopting thefollowing steps:
- The total number of electrons required forwriting the structures are obtained byadding the valence electrons of thecombining atoms. For example, in the $CH _4$ molecule there are eight valence electronsavailable for bonding.
- For anions, each negative charge wouldmean addition of one electron. Forcations, each positive charge would result in subtraction of one electron from the totalnumber of valence electrons. For example,for the $CO _3{ }^{2-}$ ion, the two negative chargesindicate that there are two additionalelectrons than those provided by theneutral atoms.
- Knowing the chemical symbols of thecombining atoms and having knowledgeof the skeletal structure of the compound, it is easyto distribute the total number of electronsas bonding shared pairs between theatoms in proportion to the total bonds.
- In general the least electronegative atomoccupies the central position in themolecule/ion. For example in the $NF _3$ andCO ${ }_3{ }^{2-}$, nitrogen and carbon are the centralatoms whereas fluorine and oxygenoccupy the terminal positions.
- After accounting for the shared pairs ofelectrons for single bonds, the remainingelectron pairs are either utilized for multiplebonding or remain as the lone pairs. Thebasic requirement being that each bondedatom gets an octet of electrons.
i. ... postulated that atoms achieve the stable octet when they are linked by chemical bonds.

… postulated that atoms achieve the stable octet when they are linked by chemical bonds.

Lewis
Debye
Charles
Sidgwick

… in 1916 developed an important theory of chemical combination between atoms known as electronic theory of chemical bonding.

Kössel
Lewis
Both a) & b)
Sidgwick

In the formation of a molecule, only the outer shell electrons take part in chemical combination and they are known as …

Backscattered electrons
Valence electrons
Primary electrons
Secondary electrons

In the $CH_4$ molecule there are … valence electrons available for bonding.

4
6
8
10

The type of bond between atoms in a molecule of CO2 is:

Ionic bond
Metallic bond
Hydrogen bond
Covalent bond.

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Read the passage given below and answer the following questions from 1 to 5.
The unusual properties of water in the Condensed phase (liquid and solid states) are Due to the presence of extensive hydrogen Bonding between water molecules. This leads To high freezing point, high boiling point, high Heat of vaporisation and high heat of fusion in Comparison to $H_2S$ and $H_2Se$. In comparison To other liquids, water has a higher specific Heat, thermal conductivity, surface tension, Dipole moment and dielectric constant, etc. these properties allow water to play a key role In the biosphere. In the gas phase water is a bent molecule with a bond angle of $104.5^\circ$ , and O–H bond length Of 95.7 pm
It is a highly polar molecule. Its orbital overlap. In the liquid Phase water molecules are associated together By hydrogen bonds. The crystalline form of water is ice. At Atmospheric pressure ice crystallises in the Hexagonal form, but at very low temperatures It condenses to cubic form.
Density of ice is Less than that of water. Therefore, an ice cube Floats on water. In winter season ice formed On the surface of a lake provides thermal Insulation which ensures the survival of the Aquatic life. This fact is of great ecological Significance. Structure of Ice Ice has a highly ordered three dimensional Hydrogen bonded structure. Examination of ice crystals with X-rays shows that each oxygen atom is Surrounded tetrahedrally by four other oxygen Atoms at a distance of 276 pm.
Hydrogen bonding gives ice a rather open Type structure with wide holes. These holes can Hold some other molecules of appropriate size Interstitially.
Water reacts with a large number of Substances. Some of the important reactions Are given below.
Amphoteric Nature: It has the ability to act as an acid as well as a base i.e., it behaves As an amphoteric substance. In the Brönsted Sense it acts as an acid with $NH_3$ and a base with $H_2S.$
$\text{H}_2\text{O}(\text{l})+\text{NH}_3(\text{aq})\rightleftharpoons\text{OH}^-(\text{aq})+\text{NH}^+_4\text{aq}$
$\text{H}_2\text{O}(\text{l})+\text{H}_2\text{S}(\text{aq})\rightleftharpoons\text{H}_3\text{O}^+(\text{aq})+\text{HS}^-\text{(aq)}$
The auto protolysis (self-ionzation) of water takes palace as follow:
$\text{H}_2\text{O}(\text{l})+\text{H}_2\text{O}(\text{l})\rightleftharpoons\text{H}_3\text{O}^+(\text{aq})+\text{OH}^-(\text{aq})$
$\text{acid-1 base-2 (acid-2) base-1}$
$\text{(acid) (base) (conjugate acid) (conjugate base)}$
Redox Reactions Involving Water: Water Can be easily reduced to dihydrogen by highly Electropositive metals.
$2\text{H}_2\text{O}(\text{l})+2\text{Na}\text{(s)}\rightarrow2\text{NaOH}\text{(aq)}+\text{H}_2\text{g}$
Thus. it is a great source of dihydrogen.
water is oxidished to $O_2$ during photosynthesis.
$6\text{CO}_2\text{g}+12\text{H}_2\text{O}(\text{l})\rightarrow\text{C}_6\text{H}_{12}\text{O}_6(\text{aq})+6\text{H}_2\text{O}{\text{l}}+6\text{O}_2\text{(g)}$
With fluorine also it is oxidised to $O_2.$
$2\text{F}_2\text{g}+2\text{H}_2\text{O}(\text{l})\rightarrow4\text{H}^+(\text{aq})+4\text{F}^-(\text{aq})+\text{O}_2\text{(G)}$
Hydrolysis Reaction: Due to high Dielectric constant, it has a very strong Hydrating tendency. It dissolves many ionic Compounds. However, certain covalent and Some ionic compounds are hydrolysed in water.
$\text{P}_4\text{O}_{10}(\text{s})+6\text{H}_2\text{O}(\text{l})\rightarrow4\text{H}_3\text{PO}_4\text{(aq)}$
$\text{SiCl}_4{\text{l}}+2\text{H}_2\text{O}(\text{l})\rightarrow\text{SiO}_2\text{(s)}+4\text{HCl}\text{(aq)}$
Hydrates Formation: From aqueous Solutions many salts can be crystallised as Hydrated salts. Such an association of water Is of different types viz., Coordinated water e.g.,

Hard and Soft Water- Rain water is almost pure (may contain some Dissolved gases from the atmosphere). Being a Good solvent, when it flows on the surface of The earth, it dissolves many salts. Presence of Calcium and magnesium salts in the form of Hydrogencarbonate, chloride and sulphate in Water makes water ‘hard’. Hard water does Not give lather with soap. Water free from Soluble salts of calcium and magnesium is Called Soft water. It gives lather with soap Easily. Temporary hardness is due to the presence of Magnesium and calcium hydrogen- Carbonates. It can be removed by:
Boiling: During boiling, the soluble $Mg(HCO_3)_2$ is converted into insoluble $Mg(OH)_2$ And $Ca(HCO_3)_2$ is changed to insoluble $CaCO_3$. It is because of high solubility product of $Mg(OH)_2$ as compared to that of $MgCO_3$, that $Mg(OH)_2$ is precipitated. These precipitates can Be removed by filtration. Filtrate thus obtained
Will be soft water.
$\text{Mg}(\text{HCO}_3)_2\xrightarrow{\text{Heating}}\text{Mg}(\text{OH})_2\downarrow+2\text{CO}_2\uparrow$
$\text{Ca}(\text{HCO}_3)_2\xrightarrow{\text{Heating}}\text{CaCO}_3\downarrow+\text{H}_2\text{O}+\text{CO}_2\uparrow$
Clark’s method: In this method calculated Amount of lime is added to hard water. It Precipitates out calcium carbonate and Magnesium hydroxide which can be filtered off.
Permanent Hardness is due to the presence of soluble salts of Magnesium and calcium in the form of Chlorides and sulphates in water. Permanent Hardness is not removed by boiling.
$\text{Ca}(\text{Hco}_3)_2+\text{Ca}(\text{OH)}_2\rightarrow2\text{CaCO}_3\downarrow2\text{H}_2\text{O}$
$\text{Mg}(\text{HCO)}_3+2\text{Ca}\text{(Oh)}_2\rightarrow2\text{CaCO}_3\downarrow+\text{Mg}(\text{OH)}_2\downarrow2\text{H}_2\text{O}$
Permanent Hardness is due to the presence of soluble salts of Magnesium and calcium in the form of Chlorides and sulphates in water. Permanent Hardness is not removed by boiling.

In the gas phase water is a bent molecule with a bond angle of:

$104.5^\circ$
$94.5^\circ$
$110.5^\circ$
$95.5^\circ$

At Atmospheric pressure ice crystallises in the … form.

Cubic
Hexagonal
Octagonal
Pentagonal

Water free from Soluble salts of calcium and magnesium is called …

hard water
dry water
soft water
None of above

Water has…. Nature.

acidic
basic
neutral
amphoteric

Water is…. Molecule.

Polar
Non- Polar
Ionic
All the above

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Once an organic compound is extracted from a natural source or synthesised in the laboratory, it is essential to purify it. Various methods used for the purification of organic compounds are based on the nature of the compound and the impurity present in it. Finally, the purity of a compound is ascertained by determining its melting or boiling point. This is one of the most commonly used techniques for the purification of solid organic compounds. In crystallisation Impurities, which impart colour to the solution are removed by adsorbing over activated charcoal. In distillation Liquids having different boiling points vaporise at different temperatures. The vapours are cooled and the liquids so formed are collected separately. Steam Distillation is applied to separate substances which are steam volatile and are immiscible with water. Distillation under reduced pressure: This method is used to purify liquids having very high boiling points.

i. Which method can be used to separate two compounds with different solubilities in a solvent?
ii. Distillation method is used to separate which type of substance?
iii. Which technique is used to separate aniline from aniline water mixture?
OR
Why chloroform and aniline are easily separated by the technique of distillation?

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The ionic character of metallic halides tends toward covalent nature as per Fajan's rule. Such covalent halides behave as non-metal in their higher oxidation states. The property to hydrolyse to give oxy-acids of the element and corresponding hydro halogen acid for most non-metallic elements proceeds exceptionally in the way, keeping oxidation number of element and halide sam in oxo-acids.
Non-polar halides are immiscible in water, as they do not show hydrolysis, but halides of some elements with empty d-orbital undergo hydrolysis. Stability of halides of the higher state is governed by the inert-pair effect.

1. How does halide undergo hydrolysis to give oxy-acids of underlined element $PCl _3$ ? (1)
2. Out of $NCl _3$ and $BCl _3$ undergoes hydrolysis to form oxy-acids? Write the chemical reaction for the correct answer. (1)
3. Out of $PbCl _4, PbF _4, PbI _4$ and $PbBr _4$ which one doesn't exist? (2)
OR
Non-Polar halides are immiscible in water. Why? (2)

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Read the passage given below and answer the following questions from (i) to (vi).
The atomic theory of matter was first proposed on afirm scientific basis by JohnDalton, a British schoolteacher in 1808. His theory, called Dalton’s atomictheory, regarded the atom as the ultimate particle ofmatter Dalton’s atomic theory was able to explainthe law of conservation of mass, law of constantcomposition and law of multiple proportion verysuccessfully. However, it failed to explain the results ofmany experiments.In mid 1850s many scientists mainlyFaraday began to study electrical dischargein partially evacuated tubes, known ascathode ray discharge tubes.Electrical discharge carried out in the modifiedcathode ray tube led to the discovery of canalrays carrying positively charged particles. Thecharacteristics of these positively chargedparticles are listed below.

Unlike cathode rays, mass of positivelycharged particles depends upon thenature of gas present in the cathode raytube. These are simply the positivelycharged gaseous ions.
The charge to mass ratio of the particlesdepends on the gas from which theseoriginate.
Some of the positively charged particlescarry a multiple of the fundamental unitof electrical charge.
The behaviour of these particles in themagnetic or electrical field is opposite tothat observed for electron or cathoderays.

The smallest and lightest positive ion wasobtained from hydrogen and was called
proton. This positively charged particle wascharacterised in 1919. Later, a need was feltfor the presence of electrically neutral particleas one of the constituent of atom. Theseparticles were discovered by Chadwick (1932)by bombarding a thin sheet of beryllium byα-particles. When electrically neutral particleshaving a mass slightly greater than that ofprotons were emitted. He named theseparticles as neutrons.J. J. Thomson, in 1898, proposed that an atom possesses a spherical shape (radiusapproximately 10–10 m) in which the positivecharge is uniformly distributed. The electronsare embedded into it in such a manner as togive the most stable electrostatic arrangementMany different names are given tothis model, for example, plum pudding, raisinpudding or watermelon. This model can be visualised as a pudding or watermelon ofpositive charge with plums or seeds (electrons)embedded into it. An important feature of thismodel is that the mass of the atom is assumed to be uniformly distributed over theatom.Rutherford and his students (Hans Geiger andErnest Marsden) bombarded very thin gold foilwith α–particles. Rutherford’s famous α–particle scattering experiment.The observations of Scattering experiment are as follows-:

most of the α–particles passed throughthe gold foil undeflected.
a small fraction of the α–particles wasdeflected by small angles.
a very few α–particles (∼1 in 20,000)bounced back, that is, were deflected bynearly 180°.

On the basis of observations andconclusions from this experiment, Rutherford proposed the nuclearmodel of atom. According to this model:

The positive charge and most of the massof the atom was densely concentrated inextremely small region. This very smallportion of the atom was called nucleusby Rutherford.
The nucleus is surrounded by electronsthat move around the nucleus with a veryhigh speed in circular paths called orbits.Thus, Rutherford’s model of atomresembles the solar system in which thenucleus plays the role of sun and theelectrons that of revolving planets.
Electrons and the nucleus are held together by electrostatic forces of attraction.

The atomic theory of matter was first proposed on afirm scientific basis by:

John Dalton
Ernest Rutherford
J.Thomson
Henry Moseley

The cathode rays start from … and move towards the….

Anode, Cathode
Centre, Anode
Cathod, Anode
Cathod, Centre

Negativelycharged particles in atoms, called…

Protons
Electrons
Neutron
Positron

The smallest and lightest positive ion wasobtained from …. and was called proton.

Oxygen
Nitrogen
Carbon
Hydrogen

Electrically neutral particles having a mass slightly greater than that of protons, these particles termed as:

Protons
Electrons
Neutron
Positron

J.J. Thomson’s atomic model is also named as:

Plum pudding
Raisin pudding
Watermelon
All the above

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