Showing posts with label 11-Chemistry. Show all posts
Showing posts with label 11-Chemistry. Show all posts

Thursday, October 7, 2021

Periodic Classification of Compounds

Mock Test Series 

 Periodic Classification of Compounds and Trends 

 Important questions

Que 1
How many elements are known to us

118 elements are known to us and which 94 are naturally occurring

Que 2
What is Dobereiner's Traids

In 1817 scientist Dobereiner arrange the elements with similar properties into group
Identify some groups having three elements each so he called his group Traida 

According to him
 when three elements in a traid were written in order of increasing atomic masses atomic mass of the middle element was the average of atomic masses of other two elements

Que 3
What is Newland law of octaves

In 1866 John newland arrange the known elements in the order of increasing atomic

He found that every eighth element has the similar properties to that of the first
He compare this to the octaves found in music therefore he called it the law of octaves

Que 4
How many elements were known at the time of mendeleev classification of periodic table


Que 5
What is the periodic law for mendeleev periodic table

"The properties of elements are the periodic function of their atomic masses "is the periodic law for the mendeleev periodic table

Que 6
What is the name given to the vertical columns and horizontal rows in the periodic table

The vertical columns are called groups
Horizontal rows are called periods

Que 7
What are the limitations of mendeleev periodic table classification

The position of the hydrogen cannot be fixed as hydrogen has both the properties of alkali and the halogens

There is no place for the isotopes of the element

Que 8
What is the basis of Mendeleev  periodic table

Mendeleev arrange the elements in order of their increasing atomic masses

Que 9
Who discovered atomic number

In 1913 Henry Moseley

Que 10
What is the basis of modern periodic table

The modern periodic table is arranged on the basis of the atomic number

Que 11
What is modern periodic law

Properties of elements are a periodic function of their atomic number

Que 12
How many vertical columns and horizontal rows are found in modern periodic table

There are 18 vertical columns known as groups

There are 7 horizontal rows known as periods

In order to understand different trends in the periodic table like valency atomic radius electronegativity metallic character non metallic character watch the attached lecture

How to find the position of an element in a periodic table just by its atomic number

Tuesday, September 28, 2021


 JEE NEET Mock Test Series of Chemistry -Hydrogen 

Multiple  Choice Questions

Que 1

 The radioactive isotope of hydrogen is

a) Hydrogen
b) Protium
c) Deuterium
d) Tritium

Ans (d)

Que 2 

What is the mass of hydrogen peroxide in one litre of 3M solution?

a) 10.2 g
b) 102 g
c) 11.3 g
d) 68 g

Ans (b)

Que 3

 Decomposition of hydrogen peroxide is prevented by

a) NaOH
b) MnO2
c) glycerol
d) oxalic acid

Ans (c)

Que 4

 Which of the following is used as a moderator in nuclear reactors?

a) Heavy Hydrogen
b) Ozone
c) Heavy Water
d) Hydrogen Peroxide

Ans (c)

Que 5 

The oxidation number of oxygen in hydrogen peroxide is 

a) 1
b) 2
c) -1
d) -2

Ans (c)

Que 6

 The strength of 20 volume of hydrogen peroxide is 

a) 13.6g/litre
b) 60.7 g/litre
c) 160 g /litre
d) 20.2 g/litre

Ans (b)

Que 7 

25 volumes of hydrogen peroxide means

a) 25%H2O2
b) 25 cm^3 of the solution contains 1 gram of  hydrogen peroxide
c) 1 cm^3 of solution liberates 25 cm^3 of O2 at NTP 
d) 25 cm^3 of the solution contains 1 mol of hydrogen peroxide

Ans ( c)

Que 8

 Ortho and para hydrogen differ in 

a) Atomic Number
b) Mass Number
c) Electron Spin in two atoms
d) Spins of neutrons 

Ans (d)

Que 9 

The structure of hydrogen peroxide is

a) Planar
b) Non Planar
c) Spherical
d) linear

Ans (b)

Que 10 

The O-O-H bond angle in  hydrogen peroxide is

a) 106°
b) 109°28'
c) 120°
d) 101.9°

Ans (d)

Que 11

Commercial 11.2 volume H2O2 solution has a molarity of

a) 1
b) 0.5
c) 11.2
d) 1.12

Ans (a)

Que 12

Water gas is a mixture of 

a) carbon dioxide and water
b) carbon monoxide and hydrogen
c) carbon monoxide and water
d) carbon monoxide and nitrogen

Ans (b)

Que 13

Hydrogen can be prepared by the action of dilute sulphuric acid on
a) Copper
b) Iron
c) Lead
d) Mercury

Ans (b)

Que 14

The degree of hardness of water is expressed in terms of

a) ppm by weight of magnesium sulphate
b) g/L of calcium carbonate and magnesium carbonate present
c) ppm by weight of calcium carbonate irrespective of whether it is actually present
d) ppm of calcium carbonate actually present in water

Ans (c)

Que 15

Permanent hardness of water is due to the presence of 

(a)bicarbonates of sodium and potassium
(b) chloride and sulphate of sodium and potassium
(c) chloride and  sulphates of calcium and magnesium
(d) bicarbonate of calcium and magnesium

Ans (c)

Que 16 

The inorganic compound obtained by auto oxidation of 2 alkyl anthraquinol is

a) H2O
b) H2O2
c) H2
d) O2

Ans (b)

Que 17 

A commercial sample of hydrogen peroxide is labelled as 10 volume its percentage strength is nearly

b) 1%
c) 9%
d) 10%

Ans (a)

Que 18

Ortho and para hydrogen have 

a ) identical chemical properties but different physical properties
b) identical physical and chemical properties
c) identical physical properties but different chemical properties
d) different physical and chemical properties 

Ans ( a)

Que 19 

Amongst H2O,H2S,H2Se,H2Te  which one has highest boiling point

a) H2O because of hydrogen bonding
b) H2Te because of higher molecular weight
c) H2S because of hydrogen bonding
d) H2Se because of lower molecular weight

Ans (a) 

Que 20 

When Zeolite which is hydrated sodium Aluminium silicate is treated with hard water the sodium ions are exchanged with

a) H+ ions
b) Ca 2+ ions
c) (SO4) 2- ions 
d) OH- ions 

Ans (b)

Que 21

Hydrogen resembles halogens in many respect for which the several factors are responsible of the following factors which one is most important in this respect

a) tendency to lose an electron to form a cation
b) tendency to gain a single electron in its valence shell to attain  stable electronic configuration
c) low negative electron gain enthalpy value
d) it's a small size

Ans ( b) 

Que 22

Arrange LiH,NaH,KH,RbH,CsH them in order of increasing ionic characters

a) LiH>NaH>CsH>KH>RbH 
b) LiH<NaH<KH<RbH<CsH
c) RbH<NaH>KH<CsH>LiH
d) RbH >CsH>KH>NaH>LiH

Ans (b)

Que 23

Which of the following hydride is electron precise hydride

a) B2H6
b) NH3
c) H2O
d) CH4

Ans (d)

Que 24

The oxide that gives H2O2 on treatment with dilute H2SO4 is 

a) PbO2
c) MnO2
d) TiO2

Ans ( b)

Que 25 

Hydrogen Peroxide is 

a) an  oxidising agent
b) a reducing agent
c) both oxidising and reducing agent
d) neither oxidising nor reducing agent

Ans (c)

Thursday, September 23, 2021

Ncert solutions - Organic Chemistry

 Ncert solutions - Organic Chemistry

The compounds obtained  from animal or plant Kingdom  are called organic compounds

Vital force Theory 
Berzelius  proposed that synthesis of organic compounds within the plants and animals requires a mysterious force the source was called vital force and theory was referred as vital force theory

In 1828  Friedrich Wohler ,obtained urea an organic compound found in urine of mammals in laboratory

In this way  first organic compound prepared in the laboratory

Organic chemistry is a chemistry of compounds of the carbon

Tetravalency of Carbon

Atomic number of carbon is 6 .Its electronic configuration is 2,4 so in order to attain   noble gas configuration carbon atom either gain or loose  four electrons but it involves   of the large amount of energy required for this so by sharing electrons with other atoms forming covalent bonds
Tendency of carbon atom to form covalent bonds is known as tetravalency of carbon


Carbon atom has a unique capacity to form bonds with other carbon atoms this property of forming bonds with the atoms of the same element is called catenation


1) sp³ hybridisation---

The carbon atoms in alkanes have sp³ hybridization
In sp³  hybridization s orbitals are attached with three p orbitals  with the Sigma bonds

These molecules are generally of tetrahedral shape eg methane 

2) sp² hybridisation--

 The carbon atoms in alkenes have sp² hybridization ie  organic compounds which have double bond contain sp² hybridization

They consists of 1 Sigma and 1 pi bond

These are planar molecules 

3) sp hybridisation -- 

The carbon compounds containing triple bond sp hybridised ie alkynes contain sp hybridisation 

Sigma and Pi Bond 

Sigma Bond --

Sigma bond is formed by end to end overlapping of bonding orbitals along the internuclear axis This  overlapping is known as head on overlap or axial overlap

Sigma bonds are stronger than Pi bonds

Pi Bond --

Pi bond is formed by sideways overlapping of the half filled atomic orbitals of bonding atoms this overlap is known as sidewise over lap  for lateral overlap
Pi bonds are found in  unsaturated compounds

Classification of organic compounds

Organic compounds are broadly divided into

1) open chain--

These compounds contain open chains of carbon atoms in their molecules the carbon change may be either is straight chain or branched chain they are called aliphatic compounds

2) Closed chain -- 

These compounds contain closed chain of atoms in their molecules they are of three types

-- Alicyclic 
This compound contains a ring of 3 or more carbon atoms in them

-- Aromatic Compounds

These compounds have a cyclic system containing at least one benzene ring the parent member of family is called benzene is a cyclic hexagon luring of 6 carbon atoms with three double bonds in the alternate positions

-- Heterocyclic Compounds 

These compounds having contain one or more atoms of either nitrogen Oxygen or sulphur in addition to carbon atoms

Functional Groups

Functional group is a group of atoms within a molecule that has a characteristic chemical behaviour of an organic compound

Watch the lecture 

What is homologous series

Homologous  series is a series of similar constituted compounds in which the members was the same functional group and have similar chemical characteristics

Characteristics of Homologous series 

1) All members can be represented by general formula 

2) Two successive members differ in their formula by ---CH 2 group 

3) All members in particular family have identical chemical properties and a proper gradation in the physical properties

4) All numbers present in particular series can be prepared by using similar methods

IUPAC Nomenclature of Organic Compounds---

In IUPAC system the name of an organic compound consist of three parts

1) Word root-- 

Word root denotes number of carbon atoms present in the chain eg C=1 is for meth C=2 for eth etc 

2) Suffix-- 
Word Root is linked to suffix which may be primary or secondary or both

Primary suffix -- it indicates the nature of linkages in the carbon atoms

ane --for single bond 

ene -- for double bond 

yne -- for triple bond 

Secondry Suffix --- it indicates the presence of functional group in the organic compound eg  alcohol -- ol 

3) Prefix -- there are many groups which are not regarded as functional groups these are regarded as substituents or side chains  these are represented as prefixes and are placed before the word root by naming a particular compound

Watch the attached lecture to understand how to write IUPAC name of any compound

Classification of carbon atoms in alkanes

Carbon atoms in an alkane is classified as primary (1°)  secondary (2°)  tertiary (3°)  and quaternary (4°) 

Watch the lecture to understand the concept 


Two or more compounds having same molecular formula but different physical and chemical properties are called isomers

The phenomenon of existence of two or more compounds using the same molecular formula but different properties is called isomerism

Types of Isomerism

Type 1

Structural Isomerism-- The compound having same molecular formula but different structures within the molecules are called structural isomers and this phenomenon is called the structural isomerism

a) Chain Isomerism -- a compound having same molecular formula but different arrangements of carbon chain within the molecule are chain isomers and this phenomenon is called chain isomerism due to this isomerism we have straight chain and branched chain of carbon compounds

-C--C---C----C.               ----C---C----C

b) Position Isomerism--  The compounds have same molecular formula but differ  in position of functional group, carbon carbon multiple bonds or substituent group are called position isomers and this phenomenon is called position isomerism

---C----C------C----OH.                  -----C-----C-----C
c) Functional Group Isomerism-- The compounds having same molecular formula but different functional groups in the molecule this phenomenon is termed as functional group isomerism

----C----C----C=O.                  -----C----C----C
                    |.                                    ||
                    H.                                    O
           Propanal                       Propanone 

d) Metamerism --- The compounds having same molecular formula but different number of carbon atoms on either side of the function code are called metamers and this phenomenon is called metamerism 

--C--C---CO---C---C               C---CO---C---C---C

e) Tautomerism -- 

This isomerism is so much different their arrangement of atoms but they exist in dynamic equilibrium with each other

Stereo Isomerism--- The isomers which have same structural formula but have different relative arrangement of atoms or group of atoms in space are called stereoisomers the phenomena is called stereoisomerism

The compounds containing double bond show cis  and trans isomerism is generally known as geometrical isomerism

The compounds which have same  structural formula birthday per in the special arrangement of atoms about the double bond shows the geometrical isomerism
The isomer in which similar atoms  or groups lie on the same side of the double bond is called exercise while the other in which they are displaced on the opposite side is called trans isomer

Watch the lecture 


Compounds which contain only carbon and hydrogen are called hydrocarbon hydrocarbons can be classified into three main categories

Saturated hydrocarbon -- The hydrocarbon which contain only single bonds are called saturated hydrocarbons they are also known as alkanes for example methane propane butane

Unsaturated hydrocarbon-- Hydrocarbons which contain double bond and triple bond are called unsaturated hydrocarbons when they contain double bond they are known as alkene when they contain triple bond they are known as alkyne 

Aromatic hydrocarbon
The  hydrocarbons which contain at least 1 special type of hexagonal ring of 6 carbon atoms with three double bonds in the alternate position is called aromatic ring or benzene ring 

How to prepare alkanes in laboratory

Alkanes can be prepared by using any of the method

1) From unsaturated hydrocarbons

Saturated hydrocarbons are converted into alkanes by catalytic hydrogenation

In this process hydrogen gas is passed in the presence of nickel platinum or palladium and as a result unsaturated hydrocarbon is converted into alkane

Alkene- +H 2 -------------- -  Alkane 

Alkanes can be prepared in laboratory by heating sodium acetate with the 16 line in a copper to the methane Gas produced is collected over Water because it is insoluble in water the whole process explained in the lecture given below

Wurtz Reaction

When alkyl halide usually bromide or iodide is treated with sodium in dry ether asymmetrical alkane containing twice the number of carbon atoms of alkyl halide is obtained this method gives alkene with even number of carbon atoms

RX+2Na+XR- -------------------R--R.  + 2NaX
                       dry ether 


Hydrocarbons with double bond are known as alkene  eg ethene ,propene 

They can be prepared by halo  alkanes

When haloalkanes are  treated by  alkali (Na OH)  in presence of alcohol  halo alkanes are converted into alkane

Sandmeyer Reaction

Benzene diazonium chloride is converted to chlorobenzene on treatment with copper chloride is known as sandmeyer reaction

Cannizaro Reaction 

Aldehydes having no Alpha hydrogen forms alcohol and acid on treatment with concentrated alkali(NaOH)

How to form iodoform compounds 

Haloalkanes are treated with sodium iodide and acetone  to form idoalkane 

Huckel Rule 
Huckel Rule is  very useful in finding weather organic compound is aromatic or not 

How to recognise whether it is aromatic compound or not  watch the lecture 

Ncert solutions - Inorganic Chemistry

 Ncert solutions - Inorganic Chemistry

S block elements

Group 1 


Mock Test Series of Hydrogen

Hydrogen was first prepared by Cavendish in 1766

Hydrogen has one electron so it has equal tendency to lose or gain one electron when it loses one electron it resembles alkali metals when it came one electron it resembles halogens

Isotopes of hydrogen

Hydrogen contains three isotopes protium(H)  deuterium(D) and tritium(T)   


Hydrogen can be prepared by electrolysis of dilute sulphuric acid or dilute sodium hydroxide using platinum electrodes

Industrial preparation

Hydrogen is prepared from water gas known as Bosch process

C+H2O- ------- C O+H2

Properties of hydrogen

Hydrogen is colourless odourless tasteless it is highly combustible and diatomic gas at room temperature

Chemical Reactions

Hard water and Soft water 

Soft water 

The water which gives lather with the soap is known as soft water soft water is fit for drinking

Hard water

The water which does not give lather with the soap is known as hard water hard water is not fit for drinking the hardness of water is of two types of temporary hardness and permanent hardness

Temporary hardness in the water is due to presence of bicarbonates of calcium and magnesium hardness can be removed by boiling or treated it with lime 

Permanent hardness in the water is due to presence of chloride and sulphate

Permanent hardness can be removed by using some special techniques for example Permutit process ion exchange process calgon process

Na 2 CO 3 sodium carbonate removes both temporary and permanent hardness of water

Ortho and Para Hydrogen

Ortho hydrogen

Molecules of hydrogen in which the spins of both the nuclei are in the same directions that is parallel nuclear spins

Para hydrogen

Molecules of hydrogen in which the spins  of both the nuclei are  in opposite direction that is they have anti parallel nuclear spin

Heavy Water

D 2 O is the symbol of heavy water electrolysis of heavy water results in deuterium

Hydrogen peroxide

H 2 O 2

Hydrogen peroxide is an unstable liquid at room temperature and 1 imposes into water


Some Important Terms

Lattice Enthalpy -- 

Lattice enthalpy is amount of energy required to break one mole of a solid salt into its ion

Greater the lattice enthalpy more will be the energy required to break the lattice

Hydration Enthalpy 

It is the amount of energy released when one mole of a solid salt gets dissolved in water

Note --  for Solubility of salt  kinetic energy change should be negative

Hydration enthalpy is more more than lattice enthalpy salt will dissolve

Hydration enthalpy is less than lattice enthalpy salt will not dissolve

Alkali Metals


General electronic configuration of s block elements is ns¹

The existence monovalent ions 

they are highly electropositive 

very strong reducing agent

Their compounds are highly soluble in water and form colourless solution

Important question answers on s block elements


Explain why sodium is less reactive than potassium?

Ans --Ionization enthalpy of potassium is less than of sodium or potassium is more reactive than sodium

Que --

Why are potassium and caesium rather than lithium used in photoelectric cells?

Ans -- Potassium and caesium have much lower ionization enthalpy therefore these metals on exposure to light easily limit electrons but lithium does not

Que. --

Which of the alkali metals sodium potassium rubidium and caesium have least melting point?

Ans -- Increase in size the strength of metallic bonding decreases there for melting point also decreases so caesium has the least melting point

Que --

Which  alkali  lithium sodium potassium caesium give the hydrated salt

Ans-- Lithium is the smallest and highest charge density so it is maximum hydrated

Que --

When burnt in air lithium forms normal oxide sodium the peroxide and the potassium superoxide why

Ans -- 

Lithium of very small size and has a strong field around it so it cannot stabilize other large anions so it forms only normal oxide where are sorry I'm being large in size and can stabilize large can oxide so it forms peroxides where as potassium being large can also stabilizer large superoxide ion forming superoxides

Que -- LiH is more stable than NaH why ? 

Ans --

Both lithium  and hydrogen have a small size and their combination has high lattice energy so  lithium hydride is more stable

Que -- Sodium metal is kept under kerosene why?

Ans -- Sodium metal is very reactive when exposed to air it reacts with oxygen moisture and carbon dioxide present in the air to prevent these reactions and protect the metal sodium is kept under kerosene

Que -- Why is LiF  almost insoluble in water whereas LiCl is soluble not only in water but is also in acetone? 

Ans -- Lithium and fluoride have a small size therefore lithium fluoride has high lattice enthalpy all the hydration enthalpy of lithium fluoride is also high but it is less than lattice enthalpy

Lithium chloride has lower lattice enthalpy than corresponding hydration enthalpy so therefore it is soluble in water has also some covalent character because of greater polarization so it is also soluble in nonpolar solvents like acetone

 Alkali metal compounds are

Sodium oxide(Na 2 O)

Sodium peroxide(Na 2 O 2)

Sodium hydroxide (Na OH)

Sodium Carbonate(Na 2 CO 3)

Its common name is washing soda

Sodium bicarbonate (Na HC O 3)

Its common name is baking soda 

Sodium Sulphate Na 2 SO 4

Its common name is salt cake

Glauber ' s Salt[Na2SO4.10H2O]

Microcosmic Salt [Na(NH 4) HPO 4]

Group 2 Alkaline Earth Metals


Group 2 of periodic table is also known as alkaline earth metals 

Outermost layer of two valence electrons
Compounds of group 2 metals

Electronic configuration--
Electronic configuration of alkaline earth metals is ns²

Ionization enthalpy--

Alkaline earth metal have low ionization enthalpy but first ionisation enthalpy of  alkaline earth metals are higher than those of alkali metals but second ionization enthalpy values of alkaline earth metals are smaller than those of alkali metals

Reactivity towards oxygen

Beryllium and magnesium are kinetically  inert towards oxygen because of the formation of a film of oxide on their surface but the reactivity with oxygen increases as we move down the group to to increasing electropositive character of the elements

Some Important compounds of Alkaline Earth Metals 

Magnesium oxide MgO
Magnesium chloride Mg Cl 2
Epsom salt MgSO4.7H2O
Magnesium carbonate Mg CO 3
Calcium oxide(Quick Lime - Ca O)
Calcium hydroxide (slaked lime - Ca OH 2)
Calcium Carbonate(limestone- Ca CO 3)
Calcium Sulphate & Gypsum(CaSO4.2H2O)

Mock test series

S block Elements

1) The concentration of chlorine lead nitrate and iron in a water sample from an underground lake was found to be 1000ppb,40ppb,100ppb,0.2ppm. water is unsuitable for drinking due to high concentration of

a) lead

b) nitrate

c) iron

d) fluoride

Ans (b)

2) Which of the following atom has highest first ionization energy?

a) Na

b) K

c) Sc

d) Rb

Ans (c)

3) Hydrogen peroxide in its reaction with KIO 4 and NH 2 OH is acting as

a) reducing  agent , oxidising agent

b) reducing agent, reducing agent

c) oxidising agent, oxidising agent

d) oxidising agent, reducing agent

Ans (a)

4) Dilute aqueous solution of sodium sulphate (Na 2 SO 4) is electrolysed using platinum electrodes the products at the anode and cathode are

a) O2,H2

b)S2 O 8 ^-2,Na

c) O2,Na


Ans (a)

5) The oxide that gives hydrogen peroxide on treatment with dilute acid is

a) Pb O 2

b) Na 2O 2

c) Mn O 2

d) TiO2

Ans (b)

6) The temporary hardness of water is due to calcium bicarbonate can be removed by adding

a) Ca CO 3

b) Ca(OH)2

c) Ca Cl 2

d) HCl

Ans (b)

7) Which of the following alkaline earth metal sulphates has its hydration enthalpy greater than its lattice enthalpy?

a) Ca SO 4

b) Be SO 4

c) Ba SO 4

d) Sr SO 4

Ans (b)

8) The material used in solar cells contain

a) Cs

b) Si

c) Sn

d) Ti

Ans (b)

9) The oxidation state of most electronegative element in the products of the reaction Ba O 2,with dil H 2 S O 4 are 

a) 0 and -1

b) -1and -2

c) -2 and 0

d) -2 and -1

Ans (d)

10) Molecular formula of Glober' s salt

a) MgSO4.7H2O

b) CuSO4.5H2O

c) FeSO4.7H2O

d) Na2SO4.10H2O

Ans ( d)

P block elements  

General electronic configuration group 13 elements is ns²np1

Que --

What is the oxidation state of boron in boric acid what is the basic city of boric acid

Ans --  Formula of Boric Acid - H3 BO 3 . Oxidation  state of boron in boric acid is +3 gas it is mono basic acid

Que --

Anhydrous  Al Cl 3 is covalent but it becomes  ionic in aqueous solution

Ans -  Energy released during hydration is greater than ionization enthalpy for ammonium so it is ionic  in solution

Que --

Explain why Aluminium though electropositive metal finds extensive use of structural materials

Ans -- Aluminium reacts with air to form a hard protective layer   of aluminium trichloride which protects it further action so it becomes passive so it is extensively used as a structural material

Que -- why  BCl 3 has zero dipole moment?

Ans -- 

It has symmetrical trigonal  structure in which all three BCl bonds are oriented at an angle of 120 degree to one another so  they cancel dipole moment of each other giving the dipole moment of zero 

Que - Why does gallium undergo disproportionation reaction?

Ans --  Gallium shows both +1 and + 3  oxidation States due to inert pair effect however its + 3 oxidation state is more stable and hence undergoes disproportionation reaction 

3Ga+ ------------- 2Ga + Ga 3+

Que -- what are silicones

Ans -- silicon sar synthetic organic silicon



 compounds  --Si--O --.  units held by Si-O--Si



 They are hydrophobic that is water repellent in nature

Que -- 

Why boron trifluoride behave as a Lewis acid

Ans -- BF 3 only 6 electrons around B and its valence shell therefore needs two more electrons to complete its octet  so it readily accept a pair of electrons from Lewis bases and behaves as a Lewis acid

Group 18 

Nobel Gases

Electronic configuration of noble gases is ns²np⁶

In their valence shell  8 electrons are present so there  octet is complete

So they are  inactive and also known as inert gases

Properties of noble gases are compromised in the lecture attached given below

Ncert solutions chemistry - Classification of Elements and Periodic Properties

 Ncert solutions chemistry - periodic Properties

MOCK Test Series

Que 1

The correct order of radii of three species


a) Ca>Ca+>(Ca)2+

b) (Ca)2+>Ca+>Ca

c) Ca+>Ca>(Ca)2+

d) Ca+>(Ca)2+>Ca

Ans ( a)

Que 2

The ionic size of Na+,Mg2+,Al3+,Si4+ follows the order

a) Na+<. Mg2+.< Al3+<. ,Si4+

b)Na+. > Mg2+. >Al3+. >,Si4+

c) Na+. >Mg2+. <Al3+>. ,Si4+

d) Na+.< Mg2+. >Al3+. <,Si4+

Ans (b)

Que 3

The correct order of ionic radii in the following isoelectronic species

a) S2->Cl->K+>Ca2+




Ans (a)


Greater the charge less the radius

Que 4

The correct order of increasing radii of the elements. Na ,Si,Al,P is 

a) Si,Al,P,Na

b) P,Si,Al,Na

c) Si,P,Na,Al

d) P,Al,Si,Na

Ans (b) 


Sodium has more ionic radius

Que 5

The correct order of increasing radii of the following elements ( Na ,Rb,K,and Mg)

a) Mg,Na,K,Rb

b) Mg,K,Na,Rb

c) Na,K,Rb,Mg

d) Na,Rb,K,Mg

Ans (a)

Rb has greater radius


Radius decreases in period and increases in group

Que 6

The penetration of the electrons in any principal shell varies as

a) s. >p. > d. >f

b) s. <p. <d. <f

c) s. >p. < d. <f

d) s.< p. >d. <f

Ans (a)

Que 7

Which of the following configuration is expected to have maximum difference in second and third ionization enthalpies

a) (1s)^2, (2s)^2 ,(2p)^2

b) (1s)^2, (2s)^2 ,(2p)^6 (3s)^1

c) (1s)^2, (2s)^2 ,(2p)^1

d) (1s)^2, (2s)^2 ,(2p)^6 (3s)^2

Ans ( a)

Que 8

In which of the following compound the ratio of anion size to the cation size have the lowest value

a) NaCl

b) KCl

c) NaBr

d) MgCl2

Ans (b)

Que 9

Which of the following process proceed with the absorption of energy ie endothermic reaction

a) F------(F)-1

b) (O-)-----(O)2-

c) Cl----(Cl)-1

d) H----(H)-1

Ans (b)


(O-) will tend to resist the addition of another electron

Que 10 

Which pair of atomic number represents s block elements

a) 7,15

b) 6,12

c) 9,17

d) 3,12

Ans (d)

Que 11

Which of the following configuration of an atom has the lowest ionization enthalpy

a) (1s)^2,(2s)^2,(2p)^6

b) (1s)^2,(2s)^2,(2p)^5

c) (1s)^2,(2s)^2,(2p)^3


Ans ( d)

Que 12

The correct order of electron gain enthalpy with fluorine chlorine bromine is

a) F. <Cl. <Br. < I

b) Cl >F >Br. > I

c) F. > Cl. <Br. < I

d) F. > Cl. >Br. <I

Ans (b)

Que 13

Which of the following group represent the collection of isoelectronic species

(At no of Cs=55,Br=35)

a) (N)3-,(F)-,(Na)+

b) (Be),(Al)3+

c) (Ca)2+,(Cs)+,Br

d) Na+,(Ca)2+, (Mg)2+

Ans. ( a) 


Atoms having same number of electrons

Que 14

The group of elements in which differentiating electron enters the antipenultimate shell of atoms

a) f block elements

b) d block elements

c) p block elements

d) s block elements

Ans (a)

Que 15 

The polarizing power of the following anions follow the order

a) (N)3->F->O2-

b) (O)2->N3->F-

c) O2->F->N3-

d) N3->O2-.>F-

Ans (d)

Recorded lectures attached below are very helpful in order to solve the different multiple questions given above in the post

Topic covered in this lecture

How to find the group and period using atomic number that is using the electronic configuration using Afbau principle

There are different properties of the elements like their ionic radius and ization enthalpy electronegativity melting point boiling point and how they varies and the periodic table that is there trends by watching the given lecture you can get the tricks to solve the different types of questions

Ncert solutions chemistry - Electrochemistry


Multiple choice questions

Que 1
Conductivity (unit siemens)  is directly proportional to area of the vessel and the concentration of solution in it and is inversely proportional to the length of the vessel then the unit of constant of proportionality is

a) Sm/mol

b) Sm^2/mol

c) S^-2m ^2 mol

d) S^2m^2/mol^2

Ans (b)

Que 2
Out of molar conductance versus √C in a strong electrolyte is

a) circular

b) linear

c) parabolic

d) sinusoidal

Ans (b)

Que 3
The quantity  of electricity required to liberate 0.1 gram equivalent of an element at the electrode is

a) 9650C

b) 96500 C

c) 965C

d) 96.5C

Ans (a)

Que 4
On passing 3  A of electricity for 50  minutes 0.1 g of metal deposits Equivalent  mass of the metal is

a) 20.5 

b) 25.8

c) 19.3

d) 30.7

Ans (c)

Que 5
EMF of the cell is

a) sum of two oxidation potential

b) sum of two potentials

c) difference of two electrode potentials

d) none of above

Ans (c)

Que 6

Cell constituted by two electrodes A/A+=-0.35 V  and  B= B/B+ = 0.42 V calculate the EMF of the cell

a) 0.07V

b) 0.77V

c) -0.77V

d) -0.07 V

Ans (b)

Que 7

Out of copper silver iron and zinc the metal which can displace all others from their salt solution is

a) silver

b) copper

c) zinc 

d) iron

Ans ( c )

Que 8 

The EMF of a cell is positive when free energy change of reaction is

a) greater than 0

b) less than 0

c) equal to 0

d) relationship of free energy change and emf

Que 9

Hydrogen electrode is placed in the solution whose pH is 10 or potential of this electrode will be

a) +0.591 V

b)  - 0.591 V

c) 0

d) none of these

Ans (b)

Que 10

When a lead storage battery is charged it acts as a

a) primary cell

b) galvanic cell

c) concentration cell

d) electrolytic cell

Ans (d)

Electrochemical cell or galvanic cell

The device in  which chemical energy released during a chemical reaction is converted to electric energy

Electrochemical series
The arrangement of metals in decreasing order of tendency to lose electrons
Watch lecture to understand what is electrochemical series on how the position of elements in the electrochemical seriesis helpful in determining various types of properties

Nern'st equation of cell

Relationship between electrode potential  and concentration of solution is all known as nernst equation


Battery is arrangement of one or more cells connected in a series and used where the chemical energy of the redox  reaction is converted into electrical energy

Two types of batteries

1) Primary Battery

Batteries  in which cell reaction occurs only once and the battery becomes that after the use over a period of time and cannot be reused again

Eg mercury cell, Leclanche cell

2) Secondry Batteries

These batteries are rechargeable ,on charging the reaction becomes reverse

Eg lead storage battery

Fuel cell

This was used as a primary source of electric energy on the moon flights these are the means by which chemical energy may be converted into electrical energy

Eg H2-O2 fuel cell

Ostwald dilution law


 Ncert solutions chemistry - Solutions

Solutions Class 11 Concepts along with numericals are explained in form of video lecture 

How to find Molarity


Molarity = 
Number of moles(solute)/volume of solution ( litre)

In the video lecture attached given below explain how to find the molarity in both Hindi and English especially the numericals based on molarity are explained The questions  are discussed in this video are

Que 1

40 gram of NaOH is dissolved in 500 ml of water find the molarity

Que 2-- 

1/10 mole of solute is dissolved in hundred gram of solvent calculate molality

Que 3

Calculate molality of 20%  by weight of NaOH solution

Que 4 
15 gm of KCl is dissolved in 1L of water find molarity


How to find Normality

Formula  of Normality
= Equivalent weight of solute / volume of solvent (litre) 

Question discussed in given lecture are 

Que 1 

Find normality of 6 gram of sulphuric acid  dissolved in 250 cm³of water 

Que 2

4 gram of NaOH  are dissolved in 200 cm³ of water find molarity


Mole fraction and Henry Law 

The lecture attached below contain explanation how to find out  solutions  of questions on mole fraction and the Henry's law

Mole fraction---
 It is ratio of mole fraction of solute to sum of  mole fraction  of solute and solvent 

Henry Law 

Solubility of a gas in a liquid at a  particular  temperature is directly proportional to pressure of gas in equilibrium with liquid


Que 1

Calculate mass percentage of benzene and carbon tetrachloride if 22 gram of benzene is dissolved in 122 gram of carbon tetra chloride 

Que 2

Calculate mole fraction of water in mixture of 13 gram of water ,108 gram of acetic acid and 92 gram of ethyl alcohol 

Que 3

Calculate solubility of methane in benzene at 298K under 760 mm of Hg where Henry constant is 4.27 ×10⁵ mm of Hg

Multiple choice questions

Questions discussed in attached video are 

1) Find isotonic solutions where  A = 0.1 M of Glucose ,B = 0.05 M of NaCl ,C= 0.05 M of BaCl2 ,D= 0.01 M of AlCl3

2) If A= 0.5 M of C2H5OH ,B= 0.1 Mg3(Po4) C= 0.250 M of KBr , D= 0.3 M of Na3Po4  .which one has highest vantHoff Factor 

3) If toothpaste of  500 gram contain 0.2 g of fluoride find concentration of fluoride in PPM

4) Find Normality of 2 M of H2SO4 

5) Find Molarity of 0.5 N of NaOH 

How to find mass percentage

Chemical Thermodynamics

 Chemical Thermodynamics

Watch the lecture to  solve questions of thermodynamics 

Chemical thermodynamics

The study of energy transformations from one form to another is a studied under thermodynamics


three types of system

Open system

The system which can exchange energy as well as matter with the surroundings for example tea in a cup

Closed System

Message kam English there is exchange of only energy with the surroundings but not the matter for example hot water in a sealed tube

Isolated System

Septum which is perfectly insulated and which cannot exchange energy and matter with the surroundings for example ice in a thermos flask

Thermodynamic properties

Intensive property

The property which does not depend upon the quantity of matter present in the system for example temperature density

Extensive property

The property which depends upon the quantity of matter present in the system for example mass volume

There are following type of processes are found in the thermodynamics

Adiabatic process

The process in which system does not exchange heat with its surroundings


Isothermal process

The process in which temperature remains constant


Isobaric process

The process in which change of state is brought about at constant pressure

dP =0

Isochoric process

The process in which volume of the system remains constant


Cyclic process

This is the process in which a system undergoes a number of different states and finally returns to its initial state for the whole process change in internal energy and change in enthalpy is zero


The quantity of energy which flows between the system and surroundings on account of temperature difference is called heat it is a path function that is depends upon the path followed

H= ms ∆t

m is the mass of substance

s is specific heat

∆t is temperature difference

Heat Capacity

The amount of the heat required to raise the temperature of the system by 1 degree Celsius 

C=q/ ∆T

if the system consists of a single substance and weight 1 gram the heat capacity of the system is known as specific heat of the system


Internal energy

The total amount of energy associated with a molecule is known as internal energy it is denoted by U

At T = constant ∆U =0


The total heat content of a system at constant pressure is called enthalpy of the system it is the sum of internal energy and product of pressure volume work it is extensive property and represented symbol by H

H= E+pV



Laws of thermodynamics

First law of thermodynamics

Energy can neither be created nor destroyed it can be changed from one form to another


∆E = q+p∆V

∆E is change in internal energy

q  is heat absorbed

W is work done

Second law of thermodynamics

For  a  spontaneous process of an isolated system the entropy change is always positive

∆S = q/T = ∆H/T

Third law of thermodynamics

The entropy of a substance becomes zero at absolute zero temperature


Importance of third law is that it is used in calculating absolute entropy is of pure substances at different temperatures

∆S= CpdT/T

Hess's Law of constant Heat

Total enthalpy change during the complete course of reaction in a single step and several steps are equal


Gibbs free energy

Images of the reactions change in enthalpy and entropy occurs simultaneously so a new function is introduced to define the spontaneity of a chemical process known as Gibbs free energy which gives a relationship between enthalpy and entropy

Known as Gibbs Helmholtz equation

∆G = ∆H-T∆S

The process is spontaneous as gibbs free energy is negative 

it is an equilibrium if Gibbs free energy is equal to 0 

and it is non spontaneous  if gibbs free energy is positive

Chemical Bonding

 Ncert solutions chemistry - Chemical Bonding

Mock Test Series

chemical bonding and molecular structure

Mock Test Series

Que 1
Isostructural species are those which have same shape and hybridization among the following identify the isostructural pairs

a) NF3 and BF3

b) BF4- and NH4+

c) BCl3 and BrCl3

d) NH3 and NO3-

Ans ( b)

BF4- and NH4 + are tetrahedral

Que 2
Hydrogen bonds are formed in many compounds the boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds the correct order of decreasing order of boiling points

a) HF>H2O>NH3

b) H2O >HF>NH3

c) NH3>HF>H2O

d) NH3>H2O>HF

Ans (b)

Que 3
In ( PO4)3- ion the formal charge on the oxygen atom is

a) +1

b) -1

c) -0.75

d) +0.75

Ans (c)

Formal charge = Total charge/no of O atom
                          = -3/4

Que 4
In ( NO3)- number of bond pairs and lone pairs of electrons on nitrogen atom are

a) 2,2

b) 3,1

c) 1,3

d) 4,0

Ans (d)

Que 6
In which of the following substances will hydrogen bond is strongest

a) HCl

b) H2O

c) HI

d) H2S

Ans (b)

Que 7
The electronic configuration of the outermost shell of the most electronegative element is

a) 2s^2,2p^5

b) 3s^2,3P^5

c) 4s^2,4p^5

d) 5s^2,5p^5

Ans ( a )

Que 8
Which element has highest ionisation enthalpy

a) 3s^2, 3p^1

b) 3s^2,3p^3

c) 3s^2,3p^2

d) 3d^10,4s^2,4p^3

Ans ( b)

Que 9
Which option represent correct bond order

a) (O2)->(O2)>(O2)+

b) (O2)-<(O2)<(O2)+


d) (O2)-<(O2)>(O2)+

Ans (b)

Que 10 
Paramagnetic Species are 

a) O2-

b) B2

c) F2

d) N2

Ans (a)

Recorded Lectures

Lewis structure

Ionic bonding

Electron Gain Enthalpy

How to find which bonding is present 

What is Bond Enthalpy

What is Bond Length

Trick to find dependence of bond angle bond length and dipole moment

Lattice Energy

Ncert solutions chemistry -States of matter

 Ncert solutions chemistry -Kinetic Theory of Gases

Multiple choice Questions

Que 1

At what temperature the RMS velocity of Sulphur dioxide be same as that of oxygen at 303 K

a) 273K

b) 606K

c) 303 K

d) 403K

Ans (b)

Que 2
The ratio of root mean square velocity to average velocity of a gas molecule at a particular temperature is

a) 1:1.086

b) 1086:1

c) 2:1.86


Ans ( b )

Que 3
Average velocity of an ideal gas molecule at303 K  is 2m/s  the average velocity at 1200 K will be 

a) 6m/s

b) 4m/s

c) 2m/s

d) 8 m/s

Ans (b)

Que 4
What is the temperature at which the kinetic energy of 0.3  mole of helium is equal to kinetic energy of 0.4  mole of   argon at 400 K

a) 400 K

b) 873 K 

c) 533 K

d) 300 K

Ans ( c) 

Que 5

Root mean square velocity of a gas is double when temperature is

a) increased 4 times

b) increased to 2 times

c) reduced to half

d) reduce to one fourth

Ans (a)

Que 6

Sample of gas has a volume of of 0.2 litres  at  1 atm pressure and 0°C At the same pressure but at 273 °C its volume will become 

 Numericals on Gaseous law

Boyles Law 

Boyles law gave a  relationship between pressure and volume of a gas at a constant temperature


PV = constant

Question which I discussed in the given lecture is

Gas at 298 K shifted from a vessel of 250 cm² capacity to that of 1 litre capacity find  change in pressure

Charles law

Charles law gives a relationship between volume and temperature of a gas at a constant pressure according to Charles law as we increase the temperature the volume of the gas increases and vice versa


Question which is explained in given lecture is 

300 ml of gas at 27° C is cooled to 3° C at constant pressure find final volume of the gas 

More Numericals on Kinetic Theory if gases


A gas occupies 15 L at a pressure of 40mm Hg what us volume when pressure increased to 75mm Hg

Que 2

A gas occupies 12 L at 0.860 atm what is pressure if volume becomes 18 L

Que 3

Given 300 ml of a gas at 25°C what is its volume at 14°C

Que 4

At 250°C a gas has volume of 7.50 L what is its volume of gas at -24° C

Que 5 

If a gas is pressured from 20 atm to 32 atm and critical temperature is 45°C what would be the final temperature in degree celcius

Que 6 

Temperature of a sample of gas in a steel container at 30kPa is increased from -10° C to 1×10³° C what is final pressure

Problems discussed in attached lecture are 

Type 1

A gas at 298 K is shifted from a vessel of 250 cm² capacity to that of 1litre capacity .Find change in pressure

Type 2 

300 ml of a gas at 27° C is cooled to 3°C  at constant pressure Find final volume

Gay Lussac Law

Numericals on combined gas Law

A gas occupies 7.6 litres at 27 ° C and 800 mm Hg  what is its volume at STP 

Concept of average root mean square and most probable velocity

Formula and Theory 

Average velocity

Vav= √8KT/πM. =√8RT/πM

Root Mean Square velocity = √3RT/M

Most Probable Velocity = √2RT/M

What is ratio between most probable average velocity and rootmean square velocity


For numericals watch the lecture

Basic Concepts of Chemistry

Ncert solutions chemistry - Structure of Atom

Whole concept in one shot

Atomic Number

= number of protons= Number of electrons

Mass Number 

No of protons+No of electrons 

Mole concept 

How to find molarity

Next lecture 

How to find mole fraction

Wave number =1/ wavelength

Energy of photon = hv

= hc / wavelength (lambda)

The number of spectral lines 

in the spectrum when the electron falls from nth level to ground level


Angular Momentum


Energy of an electron in an orbit

E=13.18Z^2/n^2 KJ /mol

E= 21.8Z^2/n^2 J/atom

E= -13.6Z^2/n^2eV/atom

Radius of orbit


Photoelectric effect

Kinetic energy of ejected electron

KE (1/2mv^2) = hv-hvo

Work function =hvo

De broglie relation

Wavelength = h/mv

Uncertainty principle

∆x×∆p= h/4π

Orbital and value of l

0 ------- s


2------- d


Sequence of energy levels


Quantum Number

There are four types of quantum numbers 

1) principal quantum number (n)
2) azimuthal quantum number(l)
3) magnetic quantum number(m)
4) spin quantum number(s)

If we have an element Sodium 
Then as we know atomic number of sodium is 11

Its configuration is 2,8,1
Or according to Afbau


For example for 2p^6

Principal quantum number is 2

Azimuthal quantum number is =1

As for s orbital it is equal to 0
For p orbital it is equal to 1
For d orbital it is equal to 2
For f orbital it is equal to 3

Magnetic quantum  number varies from
 (-l to +l)
So m= -1,0,+1

Spin quantum number

Spectrum of hydrogen atom

When any electron jumps from one shell to another either by absorbing or emission of energyenergy spectral lines are emitted from atom 

There are different series

Numericals on hydrogen spectrum

Wave length of spectral lines emitted can be calculated by using formula

There is a relationship  between
 wavenumber and wavelength 
wave number~1/wave length

Que --
 what is the frequency of the spectral line limited when the electron in n=  3 in hydrogen atom de exites  to the ground state Rydberg  constant is 109737cm^-¹

Important questions  which are useful for  questions  asked in different competitive exams are discussed in attached lecture
Que -- If ¹H1,²H1, ⁴He2,⁸Li 3 all have one  number of electrons is there is a transition of electron from n =2, n = 1 find the relationship between the wavelength emitted

Que -- 
If an atom is in nth  excited state it comes to first excited state by emitting 10 different wavelengths find the value of the end

Que --
 A hydrogen atom in its ground state is irradiated by light of wavelength 970 A° if HCF is equal to 1237×10^-⁶ find the energy of the incident light

 Que --Find the ratio of maximum wavelength of lyman series to maximum wavelength of the Pashen  series

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