CLASSIFICATION OF ELEMENTS AND PERIODIC TABLE- COMPLETE NOTES

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जवाहर नवोदय विद्यालय कक्षा 11  session  2022-23 में प्रवेश के लिए परिणाम घोषित

नवोदय विद्यालय समिति ने शैक्षणिक वर्ष 2022-23 के लिए कक्षा 11 में प्रवेश के लिए परिणाम घोषित कर दिया गया है। जिन छात्रों ने जवाहर नवोदय विद्यालय में कक्षा 11 में प्रवेश हेतु आवेदन किया है वो सम्बंधित जिले के विद्यालय से सम्पर्क कर अपना परिणाम जान सकते है अथवा नीचे दिए लिंक पर जाकर देख सकते है। 

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Collision theory

 Collision theory

☝It states that:

☝According to collision theory the molecules collides with great kinetic energy in order to bring about a chemical reaction.

 The molecules of the reacting species collide through the space in a rectilinear motion.

Rate of a chemical reaction is proportional to the number of collisions between the molecules of the reacting species.

The molecules must be properly oriented.

☝Rate of successful collisions ∝ Fraction of successful collisions X Overall collision frequency.

☝The number of collisions per second per unit volume of the molecules in a chemical reaction is called collision frequency (Z).

Let A+B --> C + D

Rate = ZABe-Ea/RT

Here ZAB = collision frequency of A and B.

☝In many reactions Rate = P ZABe-Ea/RT

Where p= steric factor which takes into account the proper orientation of the molecules participating in a chemical reaction.

 

PROBLEM.   The activation energy for the reaction 2HI(g) → H2 + I2(g) is 209.5 kJ mol-1 at 581 K. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?

SOLUTION.   Ea = 209.5 kJ mol - 1 = 209500 J mol - 1

T = 581 K

R = 8.314 JK - 1 mol - 1

Fraction of molecules of reactants having energy equal to or greater than activation energy is as follows:

x = e-Ea/RT

ln x = -Ea/RT

log x = Ea/2.303RT

log x = 209500 J mol-1/2.303 X 8.314 J K-1 mol-1 X 581 = 18.8323

x = antilog (18.323)

= antilog 19.1977

= 1.471 X 10-19

Activation energy and Maxwell’s distribution of energies

Temperature Dependence of  the Rate of a Reaction 

☝Most of the chemical reactions are accelerated by increase in temperature.

For example, in decomposition of N2O5, the time taken for half of the original amount of material to decompose is 12 min at 50o C, 5 h at 25o C and 10 days at 0o C.

☝It has been found that for a chemical reaction with rise in temperature by 10°, the rate constant is nearly doubled.

☝The temperature dependence of the rate of a chemical reaction can be accurately explained by Arrhenius equation .It was first proposed by Dutch chemist, J.H. van’t Hoff but Swedish chemist, Arrhenius provided its physical justification and interpretation.

                         K = A e-Ea/RT

Where,

k = Rate constant     A= Frequency factor

e = mathematical quantity  Ea= activation energy

R = gas constant                 T = kelvin temperature

Activation energy

☝The minimum quantitiy of external energy required for the conversion of reactant into product or to produce an unstable intermediate is called activation energy. It is E  

☝Rate of reaction is inversely proportional to the activation energy.

☝Therefore, greater value of activation energy leads to lower rate of reaction and increased influence of temperature change on the rate constant.

☝Reaction coordinates represents the profile of energy change when reactants change into product i.e. The energy profile of a chemical reaction is a representation of the most favourable energetic pathway for the reactants to be transformed into the products.

☝All the molecules in the reacting species do not have the same kinetic energy. since it is difficult to predict the behaviourof any one molecules with precision.

☝ This is due to collisions between the moving molecules so that their energies are transferred from one molecule to another. 

☝ Ludwig Boltzmann and James Clark Maxwell used statistics to predict the behaviour of large number of molecules.  If the energy of molecules are plotted against the corresponding fraction of molecules, NE/NT with a given energy at a particular temperature, a curve is obtained. This is called Maxwell’s distribution of energies( given by Ludwig Boltzmann and James Clark Maxwell).

1) The fraction of molecules having very low or very high energies is very small.

2) Most of the molecules have  intermediate kinetic energies as shown by the peak in the graph. 

      This peak corresponds to most probable kinetic energy i.e. kinetic energy of maximum fraction of molecules.

3) E corresponds to minimum or threshold energy required for effective collisions. The molecules having energy equal to or greater than E will result in the formation of products and this fraction of molecules capable of effective collisions is very small.

4) For reactions having low values of E, there will be larger fraction of colliding molecules which produce effective collisions and hence, rate of the reaction will be high.

      If the value of E for a particular reaction is high, then only a few collisions will be sufficiently energetic to give products while all other collisions will be ineffective. The reaction will proceed very slowly.

Effect of increase in temperature on the number of effective collisions

a) The curve at higher temperature gets shifted towards the right indicating that at higher temperature, the molecules have higher energies.

b) The curve at higher temperature is flatter than that at lower temperature which also indicates that the number of molecules with higher energy content have increased.

c) The number of molecules possessing energies equal to or greater than E, is proportional to area abcd at temperature T1, and area abef at temperature T2. The area abef is roughly twice as large as abcd.

Since the rate of reaction depends upon the number of molecules which possess energies larger than activation energy (for effective collisions), it may be interpreted that the fraction of molecules possessing activation energy has increased approximately two times and thereby, increases the rate by two times for a rise of 10 degrees.

Increase in the rate of reaction with the rise in temperature is mainly due to the increase in number of effective collisions.

d) fraction of molecules NE/NT = e-Ea/RT

Arrhenius equation

• The formula used to calculate the energy of activation and justify the effect of temperature on rate of reaction is called Arrhenius Equation.
• It is given by the formula,

K = A e-Ea/RT

Where,

k = Rate constant     A= Frequency factor

e = mathematical quantity  Ea= activation energy

R = gas constant                 T = kelvin temperature

☝The factor e-Ea/RT corresponds to the fraction of molecules that have the kinetic energy greater than Ea.

Thus, it has been found from Arrhenius equation that increasing the temperature or decreasing the activation energy will result in an increase in the rate of the reaction and an exponential increase in the rate constant.

Taking natural logarithm of both sides of equation

The plot of ln k vs 1/T gives a straight line with

(since A is constant for a given reaction)

k1and k2 are the values of rate constants at temperatures T1 and T2 respectively.

Subtracting equation form, we obtain

Effect of Catalyst 

☝ A catalyst is a substance which increases the rate of a reaction without itself undergoing any permanent chemical change

2KClO3 -----> 2 2 KCl + 3O2    (MnO2 as catalyst)

characteristics of catalyst-

☝catalyst provides an alternate pathway or reaction mechanism by reducing the activation energy between reactants and products 

☝ it lower the value of activation energy, faster will be the rate of a reaction. 

☝A small amount of the catalyst can catalyse a large amount of reactants. 

☝A catalyst does not alter Gibbs energy, ΔG of a reaction. 

☝It catalyses the spontaneous reactions but does not catalyse nonspontaneous reactions. 

☝It is also found that a catalyst does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster, that is, 

☝it catalyses the forward as well as the backward reactions to the same extent so that the equilibrium state remains same but is reached earlier.

Collision Theory

According to this theory, 

the reactant molecules are assumed to be hard spheres and reaction is postulated to occur when molecules collide with each other.

👍the rate of chemical reactions depends on 

a. activation energy  

b.collision frequency (Z)- The number of collisions per second per unit volume of the reaction mixture is known as collision frequency (Z)

For a bimolecular elementary reaction A + B → Products 

rate of reaction can be expressed as 

Rate = ZAB e -Ea/RT

c.Steric or probability factor (P)-The proper orientation of reactant molecules lead to bond formation whereas improper orientation makes them simply bounce back and no products are formed. 

To account for effective collisions,molecules must be properly oriented i.e.

Rate = PZAB e -Ea/RT

Next Collision Theory

Rate determining step

  Rate determining step

• The slowest step during a chemical reaction determines the overall speed of a reaction towards completion is called rate determining step.
• Let us consider the following reaction,

NO2(g)+CO(g)→NO(g)+CO2(g)

• The elementary steps of the reaction are as follows: 

Step 1:   NO2+NO2→NO+NO3 (Rate constant = k1, slow)

Step 2: NO3+CO→NO2+CO2 (Rate constant = k2, fast)

• As the first step is the slowest step in the reaction it will determine the rate of the overall reaction. Therefore Step1 is the rate determining step of the given reaction and hence the rate expression for the given reaction is the product of rate constant and the reactants of this step.

Rate = k1[NO2][NO2]=k1[NO2]2

Father of various subjects/faculties

Father of History : Herodotus

Father of Mathematics : Archimedes

Father of Economics : Adam Smith

Father of Botany : Theophrastus

Father of C language : Dennis Ritchie

Father of Geometry : Euclid

Father of Biology : Aristotle

Father of Blood groups : Landsteiner

Father of Ayurveda : Charaka

Father of Electronics : Ray Tomlinson

Father of Medicine : Hippocrates

Father of Physics : Albert Einstein

Father of Robotics : Nikola Tesla

Father of Homeopathy : Samuel Hahnemann

Father of Internet : Vinton Cerf

Father of Law : Cicero

Father of Algebra : Diophantus

Father of Architecture : Imhotep

Father of Genetics : Gregor Johann Mendel

Father of Electricity : Benjamin Franklin

Father of Microbiology : Louis Pasteur

Father of Modern Chemistry : Antoine Lavoisier

Father of Trigonometry : Hipparchus

Father of Nanotechnology : Richard Smalley

Father of Periodic table : Dmitri Mendeleev

Father of Search engine : Alan Emtage

Father of the American Constitution : James Madison

Father of the Green Revolution in India : M.S Swaminathan

Father of Statistics : Ronald Fisher

Father of Surgery (early) : Sushruta

Father of Taxonomy : Carolus Linnaeus

Father of Robotics :; Al-Jazari

Father of Video game : Thomas T. Goldsmith, Jr.

Father of World Wide Web : Tim Berners-Lee

Father of Zoology : Aristotle

Father of the Green Revolution : Norman Ernest Borlaug

Ammendments in indian flag code - Har Ghar Tiranga

पहले तिरंगा फहराने का ये नियम

यह नियम था कि जब राष्ट्रीय ध्वज को खुले स्थान पर फहराया जाता है तो जहां तक संभव हो इसे सूर्योदय और सूर्यास्त तक ही फहराया जाना चाहिए,चाहे फिर मौसम कैसा भी हो.

                गृह सचिव ने अपने पत्र में कहा कि यह कदम नागरिकों को ‘हर घर तिरंगा’ समारोह में हिस्से लेने और अपने घरों में राष्ट्रीय ध्वज को फहराने के लिए प्रोत्साहित करने के उद्देश्य से उठाया गया है. इस वर्ष हम आजादी का अमृत महोत्सव मना रहे हैं आइए हम हर घर तिरंगा आंदोलन को मजबूत करें. 13 से 15 अगस्त के बीच घर में तिरंगा फहराएं. केंद्रीय गृह सचिव ने अपने पत्र में कहा कि सरकार को उम्मीद है कि 13 अगस्त को करीब 30 करोड़ घरों में तिरंगा फहराया जाएगा.

अब तिरंगा फहराने का ये नियम-

आजादी का अमृत महोत्सव' के तहत 'हर घर तिरंगा' अभियान शुरू करने की तैयारी कर रही केंद्र की मोदी सरकार ने एक अहम फैसला लिया है। स्वतंत्रता के 75वें वर्ष में देश के ध्वज कानून में बदलाव किया गया है। केंद्र सरकार ने लोगों को अपने घरों या खुले स्थानों पर दिन और रात, दोनों समय तिरंगा फहराने की अनुमति दी है।

अब पॉलिएस्टर से बने तिरंगे का भी इस्तेमाल किया जा सकता है

वहीं एक अन्य अहम फैसले के तहत अब पॉलिएस्टर और मशीन से बने राष्ट्रीय ध्वज का भी उपयोग किया जा सकता है। झंडा कानून में बदलाव में कहा गया है कि राष्ट्रीय ध्वज हाथ से काता जाएगा और हाथ से बुना या मशीन से बनाया जाएगा। यह कपास/पॉलिएस्टर/ऊन रेशमी खादी से बना होगा। पहले मशीन और पॉलिएस्टर से बने तिरंगे के इस्तेमाल की अनुमति नहीं थी।

अजय भल्ला ने लिखा, 'राष्ट्रीय सम्मान के अपमान को रोकने के लिए भारतीय ध्वज संहिता 2002 और अधिनियम, 1971 के तहत तिरंगे का प्रदर्शन, फहराना और उपयोग किया जाता है। इसके कुछ प्रावधानों में 20 जुलाई 2022 से बदलाव किया गया है। इसके तहत व्यक्ति अपने घर पर या खुले स्थान पर दिन और रात दोनों समय तिरंगा फहरा सकेगा।'

बता दें, मोदी सरकार ने 'हर घर तिरंगा' अभियान का ऐलान किया है। इसके तहत अगले महीने 13 से 15 अगस्त तक हर घर पर तिरंगा फहराने की अपील की गई है। सरकार का दावा है कि इस दौरान 20 करोड़ घर में राष्ट्रीय ध्वज फहराया जाएगा। इससे युवाओं में देश प्रेम की भावना पैदा होगी। वहीं कांग्रेस इस पहल का भी विरोध कर रही है।

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