Showing posts with label 12-Chemistry. Show all posts
Showing posts with label 12-Chemistry. Show all posts

Wednesday, October 6, 2021

NCERT Solutions -Chemistry -Coordination compounds

 NCERT Solutions -Chemistry -Coordination compounds


A compound in which the central metal atom is linked to a certain number of ions or neutral molecules by coordinate bonds is called coordination compound
Coordination entity coordination entity constituted a central metal atom or I am wanted to be a fixed number of a positively charged ions or neutral molecules called ligands

The particular attach video explain in detail how will you name the coordination compounds

Naming of coordination compounds



What is ligand
An atom or molecule or iron which can donate a pair of electrons to the central metal ion or atom is called ligand they are of two types negative ligand and neutral ligands

Chelate 
When a polydentate ligand upon coordination with metal results in the formation of a ring then the complex is called chilate

Denticity
What is the number of coordinating sites present in a ligand

What are ambidentate ligands

Emono dine date lagan which can co-ordinate with the central atom to more than one site are called ambidant ligands

What is oxidation state of a central metal atom
Oxidation state of Central metal atom is the charge it would carry if all the ligands are removed along with the electron pairs that are shared with central atom
Watch the attached video lecture given below in order to find the oxidation number of any coordination compound

How to find oxidation number 


What is coordination number
The total number of ligands attached to a central metal ion is called coordination number of that ion

What is the spectrochemical series

The arrangement of ligands in order of their increasing crystal field splitting energy values is called spectrochemical series

What is crystal field splitting energy

When ligands approach a transition metal ion the day orbitals split into two sets one with lower energy and other with higher energy the difference of energy between the two sets of orbitals is called crystal field splitting energy if this energy is less than pairing energy the fourth electron enters one of the easy orbitals giving the configuration of t3 to g eazy one does forming high spin complexes these ligands for which crystal field splitting energy is less than pairing energy are called weak field ligands

If the crystal field splitting energy is greater than the pairing energy then it is called strong field ligands

What is effective atomic number

EAN. Effective atomic number is a total number of electrons possessed by the central metal atom or ion in the complex including those gained from the ligands bonded to it is ligand donate a pair of electrons to the metal atom or ion

Formula to calculate effective atomic number

(Atomic number-oxidation number)+2×coordination number




NCERT solutions class 12 -Chemistry-Solid state

 NCERT solutions class 12 -Chemistry-Solid state

Solid are the substances which have definite shape and definite volume solids are of two types crystalline solids and amorphous solids

 unit cell

The smallest three-dimensional portion of complete crystal lattice is called unit cell

There are generally 3 types of cubic unit cell

Primitive cell body centred cell and face centred cubic unit cell

In primitive cubic unit cell the constituent particles at all the corners of the unit cell only number of particles present per unit cell is 1

In body centred cubic unit cell all the constituent particles at all the corners as well as other body centre of the unit cell

Number of particles present per unit cell is equal to 2

Centre cubic unit cell constituent particles at all the corners as well as at the centre of each face of a cubic unit cell
Number of particles present per unit cell is 4

What is coordination

The number of squares with which one is fair is in contact is called its coordination number
For example coordination number in hexagon close packing and cubic close packing is 12
Interstitial sites
Interfaces present in the close packing of squares in a crystal are called boy as they are of three types

Cubic void
octahedral void
 and tetrahedral void

Watch the attached lecture given below in order to understand different types of patterns which are found in solids


Mera generally two types of defects found in solids
Schottky defects and frenkel defects

Schottky defects

When equal number of cations and anions are missing from their lattice sides so that electrical neutrality is maintained then this defect is called Schottky defect

Frenkel defect
Venkat iron ore and iron is missing from its latest site and occupies the interstitial site so that electrical neutrality is maintained then this defect arises

How to find Density of solid
Watch the attached lecture in order to understand how to find the density of solid in the particular questions


Practice questions

If a solid is body centred cubic structure and its density is 8.55g/cm^3 calculate atomic radius using its atomic mass 92.9

Ans -- r= 1.43×10^-10

Wednesday, September 29, 2021

Jee Mock Test Series -Chemistry-Redox Reactions

 Jee Mock Test Series -Chemistry-Redox Reactions

Mutiple choice questions

Que 1 
The more positive the value of E° the greater is the tendency of the species to get reduced using the standard electrode potential of redox couples given below find out which of the following is the strongest oxidizing agent








Ans ( d )

Que 2
E° values option relics are given below on the basis of these values choose the correct option





Ans (d)

Que 3
Find out the pair between which redox
 reaction is not feasible






Ans (d) 


Que 4 
Identify the disproportionation reaction






Ans (d)

Que 5 
Which of the following elements does not show the disproportionation  tendency

a) Cl
b) Br
c) F
d) I

Ans (c)

Que 6 
A compound contains atoms of three elements A, B,C oxidation number of  A is.   + 2 B is + 5 and  C - 2 and the possible formula of the compound is 

a) A3(BC4)2
b) A3(B4C)2
c) ABC2
d) A3(BC3)2

Ans ( d)

Que  7

An electrochemical cell has two half cell reactions





The cell voltage is 

a) 2.71 V

b ) 2.03 V

c) - 2.71 V

d) -2.03 V

Ans ( a)

Que 8 

Oxidation state of sulphur from left to right 












a) +6,0,0,+6

b) +5,0,0,+5

c) +3,+1,+1,+3

d) +4,+1,+1,+4


Ans ( c) 


Que 9 


Oxidation state of chromium is 












a) +10

b +6

c) +3

d) +2


Ans ( b)


Que 10 


Electrode potential of hydrogen electrode is

a) 0

b) +1

c) -1

d) none of these


Ans ( a)


Que 11


In the Redox reaction 

x KMnO4  +  NH3 ----------- y KNO 3 + MnO 2 + KOH + H2 O

a) x= 4, y= 6

b) x= 8 ,y= 6

c) x= 8 ,y= 3

d x= 4 ,y= 3


Ans  (c)


Que 12

In the balance reaction find a,b,c ,d






a) 5,6,3,3

b) 5,3,6,3

c) 3,5,3,6

d) 5,6,5,5


Ans ( a )


Que 13


Which of the following is a redox reaction










Ans ( d )


Que 14




Ans ( a) 


Que 15 


The strongest oxidising agent is 





Ans ( c) 


Que 16 

Standard Electrode potential of X,Y, Z is 
-1.2 V ,+0.5 V ,-3.0 V The metal having strongest reducing power


a) X

b) Y

c) Z

d ) none of these


Ans ( c)


Que 17 

In a standard hydrogen electrode the concentration of hydronium (H+) 
ions

a) 0.1M

b) 1 M

c) 10 M

d) not fixed 

Ans (b)


Que 18


Galvanic cell which of the following statement is correct

a) anode is negatively charged

b) cathode is positively charged

c) reduction occurs at anode

d) standard EMF of the cell is always zero

Ans ( c )


Que 19

In which of the following   S  has highest oxidation State

a) Na2 S4 O6

b) S2 Cl 2

c) S8

d) H2 SO 4

Ans ( d )


Que 20 

Oxidation state of N in HNO3

a) +3

b) -3

c) -1/3

d) +1/3

Ans ( c) 


How to balance equation using Hit and Trial method 





How to find oxidation number

Oxidation Number 
 
The charge which an atom of the element has in its iron or appears to have when present in the combined state with the other atoms is called oxidation number
Oxidation number of an element can be zero it may have fractional values also

Procedure for the calculation of oxidation number

Write down the formula of the given molecule ion leaving some space between the atoms

Write oxidation number on top of each atom in case of the atom whose oxidation number has to be calculated write x

Beneath the formula write down the total oxidation number of each elements X oxidation number of each atom with the number of atoms of that kind in the molecule and write the product in the bracket



Equate  the sum of the oxidation number equal to zero for  neutral molecule and equal to charge on the ion and solve for the value of the x





Eg H2 S

Oxidation number of hydrogen is + 1 then the oxidation number of Sulphur be x

H2S---

2×1+x=0

x=-2
Oxidation number of sulphur is -2

In order to understand detail concept of oxidation number watch the lecture






How to find which element is oxidised or which one is reduced

Oxidation - it is a process in which one or more electrons are lost





Reduction - it is a process in which one or more electrons are gained






Oxidising Agent --.  It is a substance which can accept one or more electrons

Reducing Agent --- It is the substance which can give one or more electrons

In a rate of reaction oxidising agent is reduced by accepting electrons and reducing agent is oxidised ed by losing the electrons

In order to understand the concept and define which is a reducing agent and which is oxidizing agent watch the lecture given below 



Electrochemical cell

The electrochemical cell is a device used to convert chemical energy produced in a Redo x reaction into electrical energy 

The electrochemical cells are also called galvanic cells or voltage cells






In Redo x  reactions oxidation and reduction occurs separately and these are called half cells

The half cell in which oxidation that is the loss of electron occurs is called oxidation half cell and the reaction taking place in it is called oxidation half cell reaction

The half cell in which reduction that is gain of electrons occurs is called reduction half cell and the reaction taking place in it is called reduction half cell reaction

Representation of an Electrochemical cell

Galvanic cell is represented by writing the anode where oxidation occurs on the left hand side and the cathode where adoption occurs on the right hand side












Some. Solved examples how to write half cell reactions--






















Electrochemical series 

Arrangement of elements in order of decreasing reduction potential values is called electrochemical series is also called activity series






Electrode potential

An electrochemical cell consists of two half cells one of the electrodes in the half cell has a higher value of reduction potential as compared to other

Oxidation potential

The tendency of an electrode to lose electrons or to get oxidized is called its oxidation potential

Reduction potential

The tendency of an electrode to gain electrons or to get reduced is called its reduction potential

Electrode potential depends upon

The nature of the metal and its ions

Concentration of the ions in the solution and the temperature

Definition of Electrode potential

The difference between the electrode potential of the two electrodes constituting an electrochemical cell is known as electromotive force for cell potential of a cell is expressed in volts

EMF = E(substance reduced) -- E(substance oxidised) 

Note --

The value of standard electrode potential is positive that is greater than zero then the substance act as oxidising agent whereas if the value of electrode potential is negative then substance act as reducing agent









Tuesday, September 28, 2021

Mock Test Series for Chemistry - Organic Chemistry

 JEE NEET Mock Test Series for Chemistry - Organic Chemistry

Mock Test Series

Que 1
In which of the following compounds the marked carbon is expected to have great positive charge?

a) 'CH3-----CH2----Cl
b) 'CH3---CH2---MgCl
c) 'CH3---CH2---Br
d) 'CH3--- CH2----CH3

Ans (a)

Que 2
The principle involved in paper chromatography is

a) Adsorption
b) Partition
c) Solubility
d) Volatility

Ans ( b)

Que 3
The IUPAC name for 







a) 1- hydroxy pentane -1,4-dione
b) 1,4-dioxopentanol
c) 1-carboxybutan-3-one
d) 4- oxopentanoic acid 

Ans (d)

Que 4 
Covalent bond can undergo fission in two different ways the correct representation involving a heterolytic fission of CH3--Br is 















Ans. (b)

Que 5
 What is the correct order of decreasing stability of following cations










Ans ( a)

Que 6 
The species having +I effect are

(a) CH3CH2
(b) ---COOH
(c) ---NO2
(d) (CH3)3C----

Ans (a,c)

Que 7 
The number of structural isomers for. C6H14 is 

a) 3
b) 4
c) 5
d) 6

Ans ( c)

Que 8 
Hyperconjugation involves overlap of the following orbitals

a) sigma-sigma
b) sigma - p orbital
c) p orbital-p orbital
d) π--π 

Ans (b)

Que 9 
Which of the following compounds will exhibit geometrical isomerism

a) 1-Phenyl -2-butene
b) 3-Phenyl-1-butene
c) 2-Phenyl-1-butene
d) 1,1-Diphenyl-1- propene

Ans ( a)

Que 10 
Which of the following has the lowest dipole moment












Ans ( b)

Que 11
Meso compounds do not show optical activity because

a) they do not contain chiral carbon atoms
b) they have non superimposable mirror images
c) they contain plane of symmetry
d) they do not contain plane of symmetry

Ans ( c ) 

Que 12
The number of optical isomers of the compound

a) 0
b) 1
c) 3
d) 4

Ans ( d)

Que 13
Among the following structures which one is not the resonating structure of other











a) I
b) II
c) III
d) IV

Ans (d)

Que 14
Which one is most nucleophilic nitrogen









Ans (a)


Que 15
The number of isomers including stereoisomers are possible for the compound having molecular formula C4 H8
 is

a) 1
b) 2
c) 3
d) 4

Ans  ( d)

Que 16 
Two possible stereo structures of  CH3CHOH.COOH which are optically active are called

a) Enantiomers
b) Mesomers
c) Diastereomers
d) Atropisomers

Ans. ( a)

Que 17 
The number of Sigma and Pi bonds present in 1,3- butadiene are respectively

a) 9 and 2
b) 8 and 2
c) 9 and 3
d) 9 and 1

Ans ( a )

Que 18 
The enolic form of ethyl acetoacetate as shown below has






a) 9 sigma and 2 pi bonds
b) 9 sigma and 1 pi bond
c) 18 sigma and 2 pi bond
d) 16 sigma and 1 pi bond

Ans (c)

Que 19 
The order of stability of the following carbo cations is








a)III>I>II

b) II>I>III

c) I<II<III

d) III<II<I

Ans ( a )

Que 20
The IUPAC name of the alkane





a) Z-3 -methyl -4-propyl-3-octene

b) E-3-methyl-4-propyl-3-octene

c) E-2-butyl-3-methyl-3-heptene

d) Z-2-ethyl-3-propyl-2-heptene

Ans (a)

Que 21
Orbital interaction between Sigma bonds of a substituent group and the neighbouring Pi orbital is known as

a) Hyperconjugation
b) Inductive effect
c) Stearic effect 
d) Dipole - Dipole interaction

Ans ( a)

Que 22
Name of the compound








a) 4 -Ethyl -3-methyloctane
b) 3- Methyl -4 - ethyl octane
c) 2-3-Diethylheptane
d) 5 -Ethyl -6- methyloctane

Ans (a)

Que 23
The compounds CH3OC3H7 and C2H5OC2H5 exhibit

a) optical isomerism
b) cis-trans  isomerism
c) metamerism
d) chain isomerism

Ans ( c )

Que 24
The reaction is 

                    H2O
(CH3)CBr------------ (CH3)3COH

a) elimination reaction
b) substitution reaction
c) free radical reaction
d) addition reaction

Ans (b)

Que 25 
The hybrid orbitals that will form the compound


          


Ans (a)   

 

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

Catenation 

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

Hybridisation 

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 



Isomerism

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
                                                |
                                                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
                                                                   |
                                                                   OH
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 




Hydrocarbons

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


                        Pd/Pt/Ni
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 


Alkene 

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 

Hydrogen


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)   


Preparation 

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


2H2O2-------2H2O+O2



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

Li,Na,K,Rb,Cs,Fr

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

Que 

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

Be,Mg,Ca,Sr,Ba,Ra

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

d)H2,O2


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

                            R

                            |

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

                            |

                            R

 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 - Surface Chemistry

 Ncert solutions chemistry - Surface Chemistry


Surface chemistry




Ncert solutions chemistry - Chemical Kinetics


Chemical Kinetics


It  is the branch of chemistry in which we study how the rate of reactions are related with each other we can easily find out the expressions with the help of rate of reaction

Rate of a Reaction

The rate of change of concentration of reactants or products in a unit time
General equation
aA+bB ---------cC+dD

Rate = - d[A]/adt

          =  - d[B]/bdt

          =  d[C]/cdt
         
          = d[D]/ddt

Rate law and Rate constant

According to law of mass action the rate of a chemical reaction is directly proportional to product of effective concentration of reactive species each raised visitable power near me not equal to respective is your stoichimetric coefficients

aA +bB---- --- product 

Rate = k[A]^a[B]^b

k is  rate constant or velocity constant or specific reaction rate
 this expression is known as rate law

Molecularity of a reaction

The number of atoms colliding with each other in a single or elementary step of chemical reaction is called molecularity of reaction
Molecularity is always a whole number
It can never be zero or fractional
It does not tell about the rate of the reaction

Order of a reaction

The sum of powers of concentration of reactants in the rate law expression is called order of chemical reaction

aA +bB---- --- product 

Rate = k[A]^a[B]^b

       Order of reaction =a +  b



Units of rate constant for different order of reactions

Generalised formula

Unit of k= (molL^-1)^1-n/s

Integrated rate expression

Zero order reaction

The reaction in which the rate of reaction is independent of the concentration of reactant is called zero order reaction

Rate =1/t{[Ao]-[A]}

First order reaction

The reaction in which rate of reaction depends upon concentration of one reactant only is called first order reaction

k = 2.303/t{loga/(a-x)}

a - -- initial concentration

(a- x) --- concentration of reactant left after time t

Second Order Reaction

The reaction rate of reaction depends upon concentration of two reactants is called second order reaction


Half life of a reaction

The time period in which the concentration of the reactant reduced to half of its initial value is called half life of the reaction

t1/2= 0.693/k 




Arrhenius Equation

Effect of temperature on the rate of reaction and rate  constant was given by Arrhenius 

k= Ae^(-Ea/RT)

Or

ln k = ln A -Ea/RT

Where 

A -- Arrhenius factor

Ea -- activation energy

R -- gas constant

If at a temperature t1 the value of rate constant is k1 and   at T2 the value of rate constant is k2

log (k2/k1)= Ea/2.303R[(T2-T1)/T1T2]


Activation energy

The minimum amount of energy absorbed by the reactant molecule such that this energy becomes equal to threshold energy thereby undergoing effective collisions for a reaction to take place is called activation energy lower the activation energy faster is the reaction






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