LAKSHYA BATCH PHYSICS WALLAH

2021-10-05 14:34:10 Happy World Teacher's Day!
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2021-10-03 07:32:02 Notes on Chemical Coordination and Regulation


Properties of hormones
(a) These are secreted by endocrine gland (biogenic in origin).

(b) Their secretions is released directly into blood (except local hormones e.g. gastrin).

(c) These are carried to distantly locate specific organs, called target organ.

(d) These have specific physiological action (excitatory or inhibatory). These co-ordinate different physical, mental and metabolic activities and maintain homeostasis.

(e) The hormones have low molecular weight e.g. ADH has a molecular weight of 600–2000 daltons.

(f) These act in very low concentration e.g. around10–10 molar.

(g) Hormones are non antigenic.

(h) These are mostly short-lived. So have a no camulative effect.

(i) Some hormones are quick acting e.g. adrenalin, while some acting slowly e.g. ostrogen of ovary.

(j) Some hormones secreted in inactive form called Prohormone e.g. Pro-insulin.

(k) Hormones are specific. They are carriers of specific information to their specific target organ. Only those target cell respond to a particular hormone for which they have receptors.

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2021-10-02 03:24:11 Final Words by Ashish sir for JEE Advanced 2021 Aspirants.

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2021-09-25 02:55:18 Notes on Coordination Compounds


Ligands: an ion or molecule capable of donating a pair of electrons to the central atom via a donor atom.

Unidentate ligands: Ligands with only one donor atom, e.g. NH3, Cl-, F- etc.
Bidentate ligands: Ligands with two donor atoms, e.g. ethylenediamine, C2O42-(oxalate ion) etc.
Tridentate ligands: Ligands which have three donor atoms per ligand, e.g. (dien) diethyl triamine.
Hexadentate ligands: Ligands which have six donor atoms per ligand, e.g. EDTA.

Chelating Ligands:

Multidentate ligand simultaneously coordinating to a metal ion through more than one site is called chelating ligand. Example: Ethylenediamine (NH2CH2CH2NH2)
These ligands produce a ring like structure called chelate.
Chelation increases the stability of complex.

Werner’s Theory:

Metals possess two types of valencies i.e. primary (ionizable) valency and secondary (nonionizable) valency.
Secondary valency of a metal is equal to the number of ligands attached to it i.e. coordination number.
Primary valencies are satisfied by negative ions, while secondary valencies may be satisfied by neutral, negative or positive ions.

Secondary valencies have a fixed orientation around the metal in space.

[Co(NH3)6]Cl3

Primary Valencies = 3 Cl-

Secondary Valencies = 6 NH3

Coordination Sphere = [Co(NH3)6]3-


Nomenclature of Complexes:

Positive ion is named first followed by negative ion.
Negative ligands are named by adding suffix - o.
Positive ligands are named by adding prefix – ium.
Neutral ligands are named as such without adding any suffix or prefix.
Ligands are named in alphabetical order.
Name of the ligands is written first followed by name of metal with its oxidation number mentioned in roman numbers in simple parenthesis.
Number of the polysyllabic ligands i.e. ligands which have numbers in their name, is indicated by prefixes bis, tris etc,
Number and name of solvent of crystallization if any, present in the complex is written in the end of the name of complex.
When both cation and anion are complex ions, the metal in negative complex is named by adding suffix-ate.

In case of bridging ligands:
[Name of the groups to the left of bridging ligand (Oxidation state)] –μ – [Name of the groups to the right of bridging ligand (Oxidation state)] – [Name of negative ion]

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2021-09-22 10:17:39 Quick Revision Strategy for IIT JEE Advanced 2021 by Expert
30 days before the examination you should follow these points-

⊙ Try to wake up early because the exam is conducted usually in the morning and afternoon shift. Your brain will take time to adjust to this new sleeping and waking up the pattern but it is mandatory to sleep early and get up early as it will increase the functioning of your brain cells and help rejuvenate it.
⊙ A daily to-do list plays a pivotal role during the revision process. Every day when you wake-up, plan your entire day. For example, cover ‘Kinematics chapter’, solve 25 questions from Physics, 10 from Mathematics.
⊙ Make it a habit of solving the previous years’ question paper on a daily basis. This will help you know your on-going preparation and analyze how well you are acquainted with solving difficult questions. The exam should be given in a similar exam condition with a timer and an OMR sheet.
⊙ Quick revision can be done with the help of flash cards and hand-written notes.
⊙ Avoid using any new study material or reference books. In this last month only revise NCERT books. If you start with any new books then it might definitely boggle your mind and panic you affecting your JEE preparation.
⊙ Once you have solved the Jee advanced sample question papers, make a habit of looking at the solutions also. These will tell you how to approach a question, the correct strategy to solve it in less time and later you can make your own strategy to tackle similar kind of questions.

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2021-09-17 20:03:18 Properties of Solids and Liquids - Revision Notes on Liquids at Rest:

Force of cohesion:- It is force between two molecules of similar nature.

Force of adhesion:- It is the force between two molecules of different nature.

Molecular range:- The maximum distance between two molecules so that the force of attraction between them remains effective is called molecular range.

Sphere of influence:- Sphere of influence of any molecule is the sphere with molecule as its center and having a radius equal to molecular range (=10-7 cm).

Surface film:- Surface film of a liquid is defined as the portion of liquid lying on the surface and caught between two parallel planes situated molecular range apart.

Surface Tension

Surface tension is the property of a liquid by virtue of which its free surface behaves like a stretched membrane and supports, comparatively heavier objects placed over it. It is measured in terms of force of surface tension.

Force of surface tension:- It is defined as the amount of force acting per unit length on either side of an imaginary line drawn over the liquid surface.

(a) T = Force/length = F/l

(b) T = Surface energy/Surface area = W/A

Units:- S.I – Nm-1

C.G.S- dyn cm-1

Additional force:-
(a) For a cylindrical rod:- F = T×2πr (Here r is the radius of cylindrical rod)

(b) For a rectangular block:- F = T×2(l+d) (Here l is the length and d is the thickness of the rectangular block)

(c) For a ring:- F = T×2×2πr (Here r is the radius of cylindrical rod)

Surface energy:-
Potential energy per unit area of the surface is called surface energy.

(a) Expansion under isothermal condition:-

To do work against forces of surface tension:-

W= T×A (Here A is the total increase in surface area)

To supply energy for maintaining the temperature of the film:-

E = T+H

(b) Expansion under adiabatic conditions:-

E = T

Force of surface tension is numerically equal to the surface energy under adiabatic conditions.

Drops and Bubbles:-

(a) Drop:- Area of surface film of a spherical drop of radius R is given by, A = 4πR2

(b) Bubble:- The surface area of the surface films of a bubble of radius R is, A = 2×4πR2

Combination of n drops into one big drop:-

(a) R = n1/3r

(b) Ei = n (4πr2T), Ef =4πR2T

(c) Ef/ Ei = n -1/3

(d) ΔE/Ei = [1-(1/n1/3)]

(e) ΔE = 4πR2T (n1/3-1) = 4πR3T (1/r – 1/R)

Angle of contact:- Angle of contact, for a pair of solid and liquid, is defined as the angle between tangent to the liquid surface drawn at the point of contact and the solid surface inside the liquid.

(a) When θ < 90º (acute):-

Fa >Fc/√2

(i) Force of cohesion between two molecules of liquid is less than the force of adhesion between molecules of solid and liquid.

(ii) Liquid molecules will stick with the solid, thus making solid wet.

(iii) Such liquid is put in the solid tube; it will have meniscus concave upwards.

(b) When θ > 90º (obtuse):-Fa
(i) Force of cohesion between two molecules of liquid is less than the force of adhesion between molecules of solid and liquid.

(ii) In this case, liquids do not wet the solids.

(iii) Such liquids when put in the solid tube will have a meniscus convex upwards.

(c) When θ = 90º:-?

Fa=Fc/√2

The surface of liquid at the point of contact is plane. In this case force of cohesion and adhesion are comparable to each other.

(d) cosθc = Tsa – Tsl/Tla

Here, Tsa,Tsl and Tla represent solid-air, solid-liquid and liquid-air surface tension respectively). Here θc is acute if Tsl < Tsa while θc is obtuse if Tsl >Tsa.

Capillarity:-

?Rise of Liquid in a Capillary Tube?Capillarity is the phenomenon, by virtue of which the level of liquid in a capillary tube is different from that outside it, is called capillarity.

Weight of liquid, W = Vρg = πr2[h+(r/3)]ρg (Here r is the radius meniscus)

If weight of meniscus is taken into account, the force of surface tension will be,

T = [r(h+(r/3)) ρg]/2 cosθ

For fine capillary, force of surface tension, T = rhρg/2 cosθ

So height, h = 2T cosθ/ rρg ओपन / कमेंट

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