Law of chemical combination किया है? | Chemistry class 11

Law of chemical combination:-

Chemical reactions take place according to cortain Law, called laws of chemical combination

There are:-

(1) Law of conservation of mass:-

=>This law was proposed by Antoine Lavoisier in 1789.

=>It states that,"In all physical and chemical change total mass of reactant is always equal to the total mass of product".

=>In another words "Matter Can neither be created nor be destroyed".

=>This law is used for balancing the chemical reactions.

(2) Law of constant proportion or Law of definite proportion

=>This law was given by "Joseph Proust" in 1799. It states that,

"A chemical compound always contain exactly the fixed proportion of elements by mass".

Eg:-(1) A sample of pure water (H2O) obtained from whatever the sources, it always contain the  fixed proportion of H and O is 2:16 or 1:8 by mass.

Eg:-(2) A sample of CO2 can be prepared in laboratory.

(1) By combustion of carbon in excess of air.

(2) By heating lime stone:

(3) By the action of hydrochloric acid on marble

(4) By heating sodium bicarbonate

In all the above process the CO2 SO produced it contains the fixed proportion of C and O i.e 12:32 or 3:8 by mass.

(3) Law of Multiple proportion

This law was given by "John Dalton" in 1803. It states that "When two different elements combine with one another to form two or more than two compounds then the mass of one of the element which combines with a fixed mass of another element produces a simple whole no. ratio with each other by mass".

The ratio of masses of oxygen which combine with a fixed mass of carbon in CO and CO2 is 16:32 or 1:2 by mass

Eg:-(2) Nitrogen combines with oxygen and form following five oxides:-

The ratio of masses of oxygen in above oxide is 4:8:12:16:20 or 1:2:3:4:5 which is a whole no. ratio

(4) Law of reciprocal proportion:-

This law was given by Richter in 1792. According to this law "when two different elements combine with a fixed mass of third element, then the ratio of their masses in which they do so is either same or some whole no. multiple of the ratio when both combine with each other by mass".

For example:-(1) The ratio of masses of C and O in CH4 and H2O= 3:8-----------(1)

The ratio of masses of C and O in CO2=3:8--------(2)

Both the ratio (1) and (2) are the same

(2) The ratio of masses of C and S in CO2 and SO2= 12:32 or 3:8----------(1)

Again the ratio of masses of C and S in CS2=12:64 or 3:16------------(2)

Both the ratio (1) and (2) are related as:-

⅜:³/16=1:2 which is whole no.multiple of each other

(5) Law of Gaseous volume:

This law was presented by Gay Lussac in 1808.

According to this law, "Gases react with each other in a simple ratio of their volume and if the product is also in  gasesous state then the volume of product produces a simple whole no. ratio with the volume of reacting gases at STP".

Model of atom | Thomson's | Rutherford's | Bohr's | Summerteld | Quantum mechanical

Thomson's Model of atom:

J.J.Thomson's was the first to propose a detailed model of atom in 1897. He proposed that that an atom consists of uniform positively charged sphare having the radius (1A°=10^-10 m) in which the electrically neutral . The total mass of an atom is spread over the atom. This model is also known as plum-pudding model.

Limitation of Thomson's Model of atom

(1) Identity of positively charged particles was not explained.

(2) This model was found wrong according to Rutherford's experiment on scatting of Alpha particles.Rutherford's Experiment on scattering of Alpha

Rutherford's experiment on scattering of Alpha

Rutherford and his co-workers carried out a series of experiment using Alpha particals. A beam of Alpha particles was bombarded against a thin foil of about 100 nm of gold, platinum, silver, copper, respectively.

The gold foil watch surrounded circular fluorescent ZnS screen whenever and Alpha particle struck the gold foil, it produces a flash of light.

Observations:- Rutherford observed the following points:-

(1) Most of the Alpha particles (about 99%) passed through the gold foil undeflected in a straight line.

(2) A few Alpha particles (about 1 in 10,000) deflected with a certain angle.

(3) A very few Alpha particles ( about 1 in 20,000) rebounce back its initial path.

(4) The deflection of Alpha particles was greather near the central portion of the atom.

Conclusion:- Rutherford found the following result about the atom:-

(1) Most of portion of an atom is empty as most of the Alpha particles passed through the gold foil undeflected in a straight line.

(2) Total mass and total positive charge of an atom is present in its Central portion called nucleus.

(3) The size of nucleus is negligible in comparision to the size of atom.

Rutherford's Atomic Model

On the basis of his Alpha particle scattering experiment, Rutherford proposed the atomic model called rutherford's Atomic model or Nuclear Atomic model. The main points of this model have been given below:-

(1) Most of the portion of an atom is empty.

(2) Total positive charge and total mass of an atom are present in its Central portion called "Nucleus".

(3) An atom consist of a heavy positively charged nucleus in which all the protons(p+) and neutrons (n) are present. Protons(p+) and neutrons (n) are collectively known as "nucleons".  i.e Nucleons= proton+ neutron = Atomic mass(A)

(4) The size of nucleus is about 10^-5th of  the size atom.

Radius of nucleus/Radius of atom=10^-13cm/10^-8cm= 10^-5

(5) the volume of nucleus is about 10^-5th of the volume of atom.

Volume of nucleus/volume of atom=(10^-13cm)³/(10^-8cm)³=10^-15

(6) The density of nucleus of an atom may be calculated as:-

(7) There is an empty space around the nucleus of an atom, called extranuclear part. In this part, electrons revolve in a circular path called "orbit".

(8) An atom is electrically neutral because total number of protons (p+) present in the nucleus is always equal to the total number of electrons (e-) around the nucleus.

Atomic no.(z)=p+=e-

(9) Electrons revolve around the nucleus in a closed orbit with very high speed. The centrifugal force acting on revolving electron is being Counter balance by the force of attraction between the electron (e-) and nucleus.

(10) Rutherford, compare the atom with solar system in which nucleus representing the sum and revolving electrons as planets. These electrons are called planetry electrons.

Drawback's of Rutherford's Atomic Model

(1) Rutherford's Atomic model could not explain the stability of atom.

[According to Neils Bohr, when the electron (e-) revolves around the nucleus, it should loss energy in the the form of electro magnetic radiation and it should come closer and closer to the nucleus following the spiral path and ultimately the electron should fall into the nucleus therehy making the atom unstable i.e the atom would collapse. But, actually it does not so as atom is stable.

(2) This theory could not explain the distribution (or arrangement) of electron into the various orbit of an atom.

(3) This theory could not explain the hydrogen spectrum.

(4) Dissimilarities between solar system and nuclear atomic model:

=>The sun and planets are very big bodies and uncharged while the nucleus and electrons are microscopic object and charged.

=>The revolution of planets around the sun is governed by gravitational forces of attraction while the revolution of electron around the nucleus is governed by electrostatic forces of attraction.

=>There is only one planet which can revolve in a particular orbit around the sun but in an atom, more than one electron can revolve in a particular orbit of the atom.

Discovery of Cathode rays(Electron) and properties||Atomic structure||Chemistry||class 11

         Atom:-An atom is the smallest particle of element having all the chemical properties of the element does not exist in free state and takes part in chemical reaction.

An atom consists of three fundamental particle like electron proton neutron.

Discovery of Cathode rays (election)

Properties of Anode rays(proton)||Anode rays का properties

      Properties of Anode rays

1- Anode rays are invisible.

2-They travel in a straight line with very high speed ranging the velocity 10⁹ to 10¹¹ cm per second.

3-They consist of flow of positively charged particles which may be proton (H^+)when H2 gas is used in discharge tube.

4-They possess kinetic energy (K.E)

5-They have penetrating power.

6-They ionize the neutral gas when passed throught it.

7-They produce fluorescence when bombarded on zins screen.

8-when Anode rays were passed between two oppositely charged plate.

These were deflected towards the negatively charged plate indicating that these rays consist of flow of positively charged particles which may be proton (H^+) when H2 gas is used.

9-The properties of anode rays depends upon the properties of electrode and the properties of the gases used in discharge tube.

10-The e/m ratio charge(charge/mass ratio) of proton is about 9.58 ×10⁴ coulomb/g

11-The relative charge of proton is +1(p^+ +H^+)

12-The absolute charge of proton is 1.602×10^-19 coulomb(SI)

13-The charge of one mole of proton is 96500 coulomb(1Farady)

14-The relative mass of a proton is nearly equal to the mass of H-atom

i.e 1.0072amu_~1amu.

15-The absolute mass of proton is 1.672×10^-27kg

Or,1.672×10^-24g.

16-The mass of 1mol proton=(6.022×10²³)×(1.672×10^-24g)

=>6.022×10²³×0.1672×10^-23g

=>(6.022×0.1672)

=>1.00689g.

17-A proton may be defined as the fundamental particle of an atom carrying unit positive charge (+1)and having the mass equal to 1.672×10^-27kg.

Whai is Coulomb's law || Coulomb's law किया हैं।

              Coulomb's law

The force acting between the two point charge is directly proportional to the product of the two charge and inversely proportional to the square of the distance between the two point charge.

Where k is proportionality constant called electrostatic force constant

It depends upon

1-Nature of medium

2-system of unit

Limitation of Coulomb's law 

What is electric field||electric field किया होता हैं।

         ELECTRIC FIELD

Coulomb was unable to explain that how does one point charge exert force on another point charge.

                     Michael Faraday was the first man who explain the mechanism of force of in interaction between the two point charge in terms of electric field.

His explanation was that a point charge experiencing force is in the electric field of another point charge who are exerting force.

Q¹=>electric field+Q²=>electric force

Electric force<=Q¹+electric field<=Q²

Properties of Electric field lines किया होता है

 1- Positive charge is the source of electric field lines but negative charge is the sink of electric field lines.

2-Number of electric field lines starting from positive charge and terminating at negative charge is proportion to the amount of charge.

3-Number of electric field lines per unit area is proportional to the strength of the electric field.

4-A tangent drawn at the point on electric field lines gives the direction of electric field.

5-Electric field lines is a continuous curve.

6-Electric field lines is perpendicular to the surface of the charged body.

7-Two electric field lines never intersect each other at a point.

8-Electric field lines is an open curve but magnetic field lines is a close curve.

Most alzebric formula

 (a+b)²=a²+2ab+b²

(a+b)²=(a-b)²+4ab

(a+b)²=(a+b)(a+b)

(a-b)²=a²-2ab+b²

(a-b)²=(a+b)²-4ab

(a-b)²=(a-b)(a-b)

a²-b²=(a+b)(a-b)

a⁴-b⁴=(a²+b²)(a²-b²)

(a+b+c)²=a²+b²+c²+2ab+2bc+2ca

(a+b-c)²=a²+b²+c²+2ab-2bc-2ca

(a-b-c)²=a²+b²+c²-2ab+2bc-2ca

a²+b²+c²-ab-bc-ca=½[(a-b)²+(b-c)²+(c-a)²]

(a+b)³=a³+b³+3ab(a+b)

(a+b)³=a³+b³+3a²b+3ab²

(a-b)³=a³-b³-3ab(a-b)

(a-b)³=a³-b³-3a²b+3ab²

a³+b³=(a+b)(a²-ab+b²)

a³-b³=(a-b)(a²+ab+b²)

a³+b³+c³-3abc=(a+b+c)(a²+b²+c²-ab-bc-ca)

a³+b³+c³-3abc=½(a+b+c)[(a-b)²+(b-c)²+(c-a)²]

•If a+b+c=0

Then a³+b³+c³-3abc=0

•If a³+b³+c³-3abc=0

Then a+b+c=0

•If a³+b³+c³-3abc=0 and a+b+c≠0

Then a= b=c

• If a³+ b³-c³+3abc=0

Then a+b-c=0

• If a³-b³-c³-3abc=0

Then a-b-c=0