NCERT PCMB OFFICIAL ™✅

2021-09-25 11:57:07 #mostimp #Notes on #Coordination_Compounds #NCERT


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] Open / Comment

2021-09-25 11:56:24 #Viroids and prions #NCERT Open / Comment

2021-09-25 11:56:11 #Viruses #NCERT Open / Comment

2021-09-25 11:55:56 #imp #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. Open / Comment

2021-09-18 14:36:39 #most_imp #Revision Notes on Liquids at Rest

This signifies, height of liquid risen (or depressed) in a capillary tube varies inversely as the radius of tube. Smaller the diameter of capillary tube, greater is the rise of liquid in it.

Tube of insufficient length:-
Rh = 2T/ρg

As, T, ρ and g are all constant, Rh = Constant

Smaller the value of h, greater will be the value of R. But liquid will never flow.

Effect of temperature affecting surface tension of liquids:-

Surface tension of a liquid decreases with an increase in its temperature.

Tθ = K (θc-θ)

Here Tθ is the surface tension at a particular temperature θ while θc is the critical temperature of the liquid and K is constant.

Effect of density:- Density of liquid also affects its surface tension. Surface tension of a liquid is given by,

T = A (ρ - ρ')n

Here, ρ is the density of liquid, ρ' is the density of saturated vapors of liquid and A is the constant depending on the nature of liquid.

Pressure difference across a liquid surface:-

(a) Plane surface:- There is no difference of pressure on the two sides of the film.

(b) Convex surface:-Pressure below the surface film must be greater than that just above it.

(c) Concave surface:- Pressure on the upper side is greater than that just below it.

General formula for excess pressure:-

Pexcess =T[1/R1 + 1/R2]

Excess pressure in liquid drop:-

Pexcess = 2T/R, Here R is the radius of liquid drop.

Excess pressure for an air bubble in liquid drop:-

Pexcess = 2T/R

Excess Pressure for an Air Bubble in Liquid Drop

Excess pressure in soap bubble:-

Pexcess = 4T/R, Here R is the radius of soap bubble.

Pressure inside an air bubble at a depth h in a liquid:- Pin = Patm+ hdg + (2T/R)

Forces between two plates with thin water film separating them:-

(a) ΔP = T (1/r – 1/R)

(b) F = AT (1/r – 1/R)

(c) If separation between plate is d, then ΔP = 2T/d and F = 2AT/d

Radius of curvature of common film:- Rcomon = rR/R-r

Capillary depression, h = 2T cos (π-θ)/rdg

Shape of liquid surface:-

(a) Plane surface (as for water – silver) if Fadhesive > Fcohesive/√2

(b) Concave surface (as for water – glass) if Fadhesive > Fcohesive/√2

(c) Convex surface (as for mercury-glass) if Fadhesive < Fcohesive/√2

Increase in temperature:-

Δθ = 3T/ρs (1/r – 1/R) or Δθ = 3T/ρsJ (1/r – 1/R) Open / Comment

2021-09-18 14:36:09 #most_imp #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

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

1.1K views11:36

Open / Comment

2021-09-17 08:15:41 Important Cities and Countries in NCERT :

1. Neanderthal man lived in : Near East & Central Asia

2. Homo sapiens Arose in : Africa

3. Erythroxylum coca is native of : South America

4. > 70% live stock population is in : India & China

5. Saccharum barberi grown in : North India

6. Saccharum officinarum grown in : South India

7. IARI : New Delhi

8. IRRI : Phillippines

9. ICWMI : Mexico

10. Taichung Native-I develops from : Taiwan.

11.IR-8 developed from : IRRI, Philippines

12. Borlaug developed semi-dwarf wheat at :
ICWMI, Mexico.

13. Jaya & Ratna developed in : India

14. Toddy is used in : South India

15. Penicillin was used during world war-II to treat : American soldiers

16. Eli lily is an : American company.

17. A company which got patent rights on basmati rice : American Company

18. Mango tree do not & can not grow in : Canada & Germany

19. Snow leopard are not found in : Kerela forests

20. High altitude places (>3500 m) : Rohtang pass near Manali & Mansarovar (in China occupied Tibet)

simple and important tricks Open / Comment

2021-09-17 08:14:23 #MOST_IMPORTANT DATE TO REMEMBR #NCERT

January:-
30- National antileprosy day.


Feb:-
4- world Cancer Day,
28- National science day

March:-
3- world wildlife day,
8- international women's Day,
2nd Thursday of march- world kidney day,
20- world sparrow day,
21- world forestry day,
22- world water Day,
24- world TB day

April:-
7- world health day,
17- world haemophilia day,
22- earth Day,
25- world malaria day,
last Saturday- veterinary day

May:-
1- labour day,
3- asthma day,
8- red cross day,
9- thalassemia day,
2nd sunday- mother's Day,
12- hypertension day,
19- hepatitis day,
22- international biodiversity day,
25- thyroid day,
31- No tobacco day

June:-
5- Environment day,
14- blood donors day,
3rd sunday- father's Day,
21- yoga day,
26- international day against drug abuse and illicit trafficking

July:-
1- Doctors day(India),
11- population day,
29- international Tiger day

Aug:-
1to7- world breastfeeding week,
12-elephant/youth day,
20- malaria day,
29- mosquito day/national sports day

Sept:-
1to7- National nutrition week,
5- world spinal chord injury day,
16- ozone day,
21- Alzheimer's day,
last Sunday- world heart day,
28- rabies day

Oct:-
1st monday- universal children day,
1- national voluntarily blood donation day/world senior citizens day,
3- world habitat day,
4- world animal welfare day,
10- mental health day,
2nd Thursday- world sight day,
16- world food Day,
21- global I2 deficiency day

Nov:-
1- world ecology day,
7- world Cancer awareness Day,
14- diabetes day,
17- epilepsy day,
21- fisheries day

Dec:-
1-AIDS day,
2- National pollution prevention in India to mark the Bhopal gas tragedy,
5- soil day,
10- human rights day,
14- nat energy conservation day,
23- kisan farmers day Open / Comment

2021-09-12 17:53:39 Full ans KEY with QUESTION Open / Comment