Articles by "class 10"

PERIODIC CLASSIFICATION OF ELEMENTS 
Dobereiner’s Triads 
In a triad the atomic weight of middle element is always equals to Arithmetic mean of other two

MERITS 
The law of triads recognise the relationship between the atomic weight and properties of element
DEMERITS 
Not every element could be grouped in the triads
Newlands Law Of Octaves 
If elements are arranged in increasing order of their atomic weight like the Octave so that 8 element shows similar properties like first element.


MERITS 
  • atomic weight are made the basis of classification
  • periodicity of properties was recognised first time
DEMERITS 
the law of Octave failed because it does not shows the existence of transition elements
Mendeleev’s Periodic Law 
The physical and chemical properties of elements are the periodic function of their atomic weight

MERITS 
correction of atomic weight are marked and undiscovered elements are predicted
DEMERITS 
  • Mendeleev could not assign a correct position to hydrogen in the periodic table as hydrogen resembles alkali metals as well as halogens.
  • It was observed that at certain places, an element of higher atomic mass Cobalt (Co=58.93) has been placed before an element of lower atomic mass Nickel (Ni = 58.71). 
  • the position of rare Earth metals elements and isotopes are ambiguous
  • Some elements placed in the same sub - group varies in their properties. Manganese is placed with halogens which totally differ in the properties 
  • the periodic table did not reflect the electronic configuration
Why Mendeleev's left some gaps in his periodic table 
Because at that time existence of some element has not been discovered mendellev  named them by prefixing Sanskrit numeral.
Modern Periodic Law 
The physical and chemical properties of elements are the periodic function of their atomic number.

MERITS 
It is the most appropriate classification till date
DEMERITS 
the position of hydrogen is still unknown
TRENDS IN MODERN PERIODIC TABLE

  1.  Atomic Size 

LEFT TO RIGHT
Number of cell remains same but electron goes on increasing to keep element  near the nucleus atomic size shrink
TOP TO BOTTOM 
as we go top to bottom number of cell keep on increasing  which results into increasing atomic size of atom
(2) Metallic And Nonmetallic Character 
LEFT TO RIGHT
metallic character decreases and non metallic character increases
REASON
Effective nuclear charge acting on the valence shell electrons increases across a period the tendency to lose electrons will decreases
TOP TO BOTTOM 
REASON 
the outermost electron are further away from the nucleus therefore they can be lost easily
Electropostive
X-e-------->++
  • Metals are electronpostive in nature.
  • They are formed by loss of electron.
Electronegative
X+e-------->X-
  • Non metals are electronegative in nature
  • They are formed by gain of electron.
Valence Electron 
Electron present in outermost shell are known as valence electron
Valency 
it is the combining capacity of an atom with other atom
example

carbon has a valency so it combined with other four atom with itself or other atom

CARBON AND ITS COMPOUNDS 

Bonding In Carbon The Covalent Bond 
The atomic number of carbon is 6 it has four electron in its outermost shell and needs to gain or lose four electron to achieve noble gas configuration

CASE 1
If carbon gain four electrons forming C4 anion but it would be difficult for the nucleus with 6 Proton to hold on 10 electron that is 4 extra electron

CASE 2
If carbon lose 4 electrons to form C4 cation  but it would require a large amount of energy. If we  remove four electron it will leave behind a carbon cation with 6 proton in its nucleus holding onto just two electron

Carbonn overcome this problem by sharing its valence electron with other atom of carbon or atom of other element 
ELECTRON DOT STRUCTURE OF AMMONIA


METHANE 
  • Methane is widely used as a fuel
  • It is a measure component of biogas
  • Major component of CNG compressed natural gas
  • It is simplest hydrocarbon formed by carbon
STRUCTURE


COVALENT BOND 
Bond formed by the sharing of an electron pair with two other  atoms are known as covalent bond
Question :- why covalent bond compound have low melting and boiling point ?
Answer:-covalent bond strong within the molecule but internal molecular forces are small this give rise to low melting and boiling point of the compound
Question :- why covalent compound are poor conductor of electricity ?
Answer:-Because electron are  share between atoms and no charged particles are found that is why covalent compound are poor conductor of electricity
VERSATILE NATURE OF CARBON
Carbon has a unique ability to form Bond with other atom of carbon giving rise to formation of large number of  molecules this property is called catenation 
CATENATION 
The unique property of carbon to form large number of bonds (single, double or triple) with itself or other atoms

SATURATED COMPOUNDS AND UNSATURATED COMPOUNDS

Saturated Compounds
compounds of carbon which are linked buy only single bond between the carbon are called saturated compounds
Unsaturated Compound
compound of carbon having double or triple bond between carbon atoms
carbon is capable of form bonds with four  other atoms of carbon atom or other monovalent atom

CHAIN,BRANCHES AND RING
SKELETON OF CARBON CHAIN
C-C-C-C
FULLFILL VALENCY

SKELETON OF CARBON CHAIN WITH BRANCH

FULL FILL VALENCY

RINGS

BENZENE RING

Structural Isomers 
those compounds which have same molecular formula but different structure are called isomers

NOMENCLATURE OF HYDROCARBONS

GENERAL FORMULA OF ALAKNE ALKENE ALKYNE

SUFIX/PREFIX USED IN NAMING CARBON COMPOUNDS









































Chemical Properties Of Carbon Compounds
Combustion 
  • carbon and its allotropic form burns in oxygen to give carbon dioxide along with release of heat and light
  • Saturated hydrocarbon give clear flame
  • Unsaturated carbon compounds give yellow flame with lot of black smoke
C+O2------>CO2 + HEAT + LIGHT
CH4+O2------->CO2+H2O+HEAT + LIGHT
CH3CH2OH+O2------>CO2+H2O+HEAT + LIGHT

why cooking vessel getting black at the bottom while cooking ?
The gas like kerosene which are used in stove used at home has inlet for Air so that a sufficiently oxygen rich mixture is burnt to give a clear blue flame when we put vessel on the stove the air holes are blocked and fuel is getting wasted this result in incomplete combustion and result in shoot deposit.
Oxidation
  • carbon compound can be easily oxidized on combustion
CH3CH2OH(ethanol)--------KmNO4+heat----->CH3OOH(ethanoic acid)

  • substance which capable of adding oxygen to other are known as oxidising agent 
  • oxidizing agent are used in above chemical reaction
ALKALINE KMNO4--->potassium permagnette
ACIDIFIED K2Cr2O7-------->potassium dichromate
Addition Reaction
Unsaturated hydrocarbon add hydrogen in the presence of catalyst Palladium or nickel to form saturated hydrocarbon known as addition reaction  

R---->ALKYL GROUP( -CH2  , -CH2CH)

Catalyst
those substance that cause a reaction to occur or proceed at a different rate without going into reaction itself are known as catalyst
use 
the reaction is commonly used in hydrogenation of vegetable oil using a Nickel catalyst
Vegetable Oil

  • unsaturated carbon chain for cooking
  • animal fat saturated carbon chain saturated fatty acid harmful for health
Substitution Reaction 
in the presence of Sunlight chlorine is added to hydrocarbon in a very fast reaction chlorine replace the hydrogen atoms one by one it is called substitution


Ethanol 
  • ethanol is liquid at room temperature
  • it is known as alcohol
  • it is active ingredient of all alcoholic drinks
  • it is a good solvent
  • it is used in medicine cough syrups
  • ethanol is highly soluble in water
  • health problem intake of small quantity of ethanol can be Lethal if taken in large amount
Reaction of Ethanol
2Na+2CH3CH2OH---------2CH3CH2ONa+H2
CH3CH2ONa( Sodium ethoxide )
CH3CH2ONH------conc H2SO4------>CH2=CH2+H2O
Ethanoic Acid
  • it is known as acetic acid
  • 5 to 8% of solution of Acetic Acid in water is called vinegar and used widely as preservative in pickles
  • melting point to 240k it often freezes during winter in cold climate call glyceryl acetic acid
  • Ester are sweet smelling substance used in making perfume and as a flowering substances
Saponification
STEP 1: CH3COOC2H5--------NaOH(base)-------->C2H5OH+CH3COOH
STEP 2: NaOH+CH3COOH---------->CH3COONa+H2O
Reaction with Carbonate and Hydrocarbonate
2CH3COOH+Na2CO3------>2CH3COONa+H2O+CO2
CH3COOH+NaHCO3------->CH3COONa+H2O+CO2
Soaps And Detergent
SOAP
DETERGENT
The Molecule Of Soaps Are Sodium Or Potassium Salt Of Long Chain Of Carboxylic Acid
 Detergent are Ammonium Sulphate Salt Of Long Chain Of Carboxylic Acid
They Did Not Give Leather In Hard Water
  They Give Leather In Hard Water
Used In Making Bathing Soap
 Used In Samples And Product For Cleaning Clothes


Cleansing Action Of Soap



the ionic end  of soap dissolves in water while the carbon chain dissolve in oil. The soap molecule thus form a structure called micelle where one end of the molecule is towards the oil droplets while the ionic end  faces outside. This forms an emulsion in water. The soap micelle thus help in dissolving the  dirt in water and we can wash our clothes clean.

MKRdezign

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