(i) An organic compound (A) is identified as toluene from its molecular formula.
(ii) (A) on reaction with chlorine gives benzyl chloride which on further reaction with NaOH produces (B).
\({ C }_{ 6 }{ H }_{ 5 }-{ { { CH }_{ 3 } } }\overset { { Cl }_{ 2 } }{ \underset { -HCl }{ \longrightarrow } } { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }Cl\overset { NaOH }{ \underset { -Nacl }{ \longrightarrow } } \underset { (B) }{ { C }_{ 6 }H_{ 5 }{ CH }_{ 2 }OH } \) 
(iii) B) on oxidation with acidified K₂Cr₂O₇ gives (C).
\({ C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }\overset { { K }_{ 2 }{ Cr }_{ 2 }{ O }_{ 7 }/{ H }^{ + } }{ \underset { (O) }{ \longrightarrow } } \underset { (C) }{ { C }_{ 6 }{ H }_{ 5 }CHO+{ { H }_{ 2 }O } } \) 
(iv) Benzaldehyde on treatment with 50% caustic soda gives (D) and (B).
\(\underset { (C) }{ { C }_{ 6 }{ H }_{ 5 }CHO } +{ C }_{ 6 }{ H }_{ 5 }CHO\overset { 50 \% }{ \underset { NaOH }{ \longrightarrow } } \underset { (B) }{ { C }_{ 6 }{ H }_{ 5 }{ CH }_{ 2 }OH } +\underset { (D) }{ { C }_{ 6 }{ H }_{ 5 }COOH } \) 

Compound	Compound Name	Formula
A	Toluene	C6H5-CH3
B	Benzyl alcohol	C6H5CH2OH
C	Benzaldehyde	C6H5CHO
D	Benzoic acid	C6H5COOH

(i) For a chemical reaction, catalyst is needed in very small quantity.
(ii) There may be some physical changes, but the catalyst remains unchanged in mass and chemical composition in a chemical reaction.
(iii) A catalyst itself cannot initiate a reaction. 
(iv) A solid catalyst will be more effective if it is taken in a finely divided form.
(v) A catalyst are specific in nature.
(vi) In an equilibrium reaction, presence of catalyst reduces the time for attainment of equilibrium and hence it does not affect the position of equilibrium and the value of equilibrium constant.
(vii) A catalyst is highly effective at a particular temperature called as optimum temperature.
(viii) Presence of a catalyst generally does not change the nature of products

Initial concentration of
AgNO₃ = 1M= IN
Quantity of current 0.75 F
Formula:
1Faraday = 1equivalent mass
Solution:
For IF current In AgNO₃ will be liberated.
For 0.75 F current 0.75 N AgNO₃ will be liberated
The concentration of AgNO₃ remaining
= 1.0 - 0.75 = 0.25 N
ஃ The concentration of AgNO₃ remaining

Degree if dissociation \(\alpha =\sqrt { \frac { { K }_{ B } }{ C } , } C\alpha =\sqrt { { K }_{ a }.C } \)
∴ \(pH=\log\frac { 1 }{ \sqrt { { K }_{ a }.C } } =\log\frac { 1 }{ \sqrt { 1.8\times { 10 }^{ -5 }\times .1 } } \)
= \(\log\frac { 1 }{ \sqrt { 1.8\times { 10 }^{ -3 } } } =\log\frac { { 10 }^{ 3 } }{ \sqrt { 1.8 } } \)
\(=3-\frac { 1 }{ 2 } \log1.8\)
\(=3-\frac { 1 }{ 2 } \times 0.2553=3-0.1276=2.8724\)
Alternating,
\(\left[ { H }^{ + } \right] =\sqrt { { K }_{ a }\times C } \)
\(=\sqrt { 1.8\times { 10 }^{ -5 }\times 0.1 } =\sqrt { 1.8\times { 10 }^{ -6 } } \)
= 1.341 x 10^-3
∴ -log [H⁺] = -log (1.341 x 10^-3)
= 3 - 0.1277 = 2.8723.

(i) It is generally expected a steady decrease in atomic radius along a period as the nuclear charge increases and the extra electrons are added to the same sub shell.
(ii) But for the 3d transition elements, the expected decrease in atomic radius is observed from Sc to V, thereafter up to Cu the atomic radius nearly remains the same.
(iii) As we move from Sc to Zn in 3d series the extra electrons are added to the 3d orbitals, the added 3d electrons only partially shield the increased nuclear charge and hence the effective nuclear charge increases slightly.
(iv) However, the extra electrons added to the 3d sub shell strongly repel the 4s electrons and these two forces are operated in opposite direction and as they tend to balance each other, it leads to constancy in atomic radii.
(v) At the end of the series, d - orbitals of Zinc contain 10 electrons in which the repulsive interaction between the electrons is more than the effective nuclear charge and hence, the orbitals slightly expand and atomic radius slightly increases.

(i) Because of its lightness and noninflammability helium is used to filling balloons for meteorological observations.
(ii) Because of its lightness it is used in inflating aeroplane tyres.
(iii) Helium oxygen mixture is used by deep sea divers in preference to nitrogen oxygen mixtures. This prevents bends when a diver comes to the surface.
(iv) A mixture of oxygen and helium is used in the treatment of asthma.
(v) Liquid helium (b.pt 4.2K) is used as cryogenic agent for carrying out various experiments at low temperatures.
(vi)It is used to produce and sustain powerful super conducting magnets of modern NMR Spectrometers and Magnetic Resonance Imaging system (MRI) for clinical diagnosis.

Molecular solids: 
In molecular solids, the constituents are neutral molecules. They are held together by weak Vander Waals forces. Generally molecular solids are soft and they do not conduct electricity. These molecular solids are further classified into three types.
(i) Non-polar molecular solids:
(a) In non-polar molecular solids constituent molecules are held together by weak dispersion forces or London forces.
(b) They have low melting points and are usually in liquids or gaseous state at room temperature.
Ex: Naphthalene, anthracene etc.,
(ii) Polar molecular solids:
(a) The constituents are molecules formed by polar covalent bonds. 
(b) They are held together by relatively strong dipole-dipole interactions.
(c) They have higher melting points than the nonpolar molecular solids. 
Ex: Solid CO₂, solid NH₃ etc.

(iii) Hydrogen bonded molecular solids:
(a) The constituents are held together by hydrogen bonds.
(b) They are generally soft solids under room temperature.
(c) Examples: solid ice (H₂O), glucose, urea etc.

Silicates are classified into various types based on the way in which the tetrahedral units, [SiO₄]^4- are linked together.
(i) Ortho silicates (Neso silicates):
The simplest silicates which contain discrete [SiO₄]^4- tetrahedral units are called ortho silicates or nesosilicates.
Examples: Phenacite - Be₂SiO₄ (Be²⁺ ions are tetrahedrally surrounded by O^2- ions)
(ii) pyro silicate (or) Soro silicates: Silicates:
Which contain [Si₂O₇]^6- ions are called pyro silicates (or) Soro silicates.
Example: Thortveitite - Sc₂Si₂O₇
(iii) Cyclic silicates (or Ring silicates): 
Silicates which contain (SiO₃)₃^2n- ions which are formed by linking three or more tetrahedral SiO₄^4- units cyclically are called cyclic silicates.
Example: Beryl [Be₃Al₂ (SiO₃)₆] (an aluminosilicate with each aluminium is surrounded by 6 oxygen atoms octahedrally)
(iv) Inosilicates: Silicates which contain 'n':
number of silicate units liked by sharing two or more oxygen atoms are called inosilicates.
Example: They are further classified as chain silicates and double chain silicates.
(v) Chain silicates (or pyroxenes):
These silicates contain [(SiO₃)_n]^2n- ions formed: by linking 'n' number of tetrahedral [SiO₄]^4- units linearly. Each silicate unit shares two of its oxygen atoms with other units.
Example: Spodumene - LiAl(SiO₃)₂·
(vi) Double chain silicates (or amphiboles): 
These silicates contains \(\left[ { Si }_{ 4 }{ O }_{ 11 } \right] _{ n }^{ 6n- }\) ions. In these silicates there are two different types of tetrahedra:
(a) Those sharing 3 vertices
(b) those sharing only 2 vertices.
Example:
Asbestos: These are fibrous and non-combustible silicates.
(vii) Sheet or phyllo silicates: 
Silicates which contain \(({ Si }_{ 2 }{ O }_{ 5 })_{ n }^{ 2n- }\) are called sheet or phyllo silicates. In these, Each [SiO₄]^4- tetrahedron unit shares three oxygen atoms with others and thus by forming two dimensional sheets.
Example: Talc, Mica etc.
(viii) Three dimensional silicates (or tectosilicates): 
Silicates in which all the oxygen atoms of [SiO₄]^4- tetrahedra are shared with other tetrahedra to form three dimensional network are called three dimensional or tectosilicates.
Example: Quartz.

(i) It exhibits both geometrical and optical isomerism
(a) Geometrical isomers:

(b) Optical isomers:

(ii) It shows two optical isomers

(iii) Ionisation isomers
Linkage isomers
[Co(NH₃)₅(NO₂)(NO₃)₂], [CO(NH₃)₅ (ONO)](NO₃)₂
(iv) Geometrical isomers