HI

2021-06-11 19:39:30 Very Important Points - Human Reproduction

Orchiopexy : When the undescended testes are brought into scrotal sac by surgical process during childhood
this process called as
orchiopexy.

Cutting of the vasa-deferens and ligation is termed as vasectomy.

Erection of penis is controlled by parasympathetic nervous system.

Ejaculation of semen is controlled by sympathetic nervous system.

Longest unstripped muscles of the body are found in the walls of uterus. (During pregnancy)

Clitoris is a homologous to the penis in the male.

Bartholin Glands : It is homologous to Cowper's gland of male

A functional mammary gland is characteristic of all female mammals.

The milk produced during the initial few days of lactation is called colostrum which contains antibodies (IgA)
absolutely essential to develop resistance for the new-born babies. Open / Comment

2021-06-11 11:59:55 P-BLOCK ELEMENT:

This block contains non-metal, semi-metal and poor metals. P-BLOCK element the last six group of the periodic table(group 13 to 18) have their own valence electron.

GROUP 13 is known as Boron group and it consist of Boron(B),Aluminium(Al),Gallium (Ga),Indium(In),and Thallium(Ti).

MNEMONIC for this group:
B A G I T

Group 14 consist of Carbon(C),Silicon(Si),Germanium (Ge),Tin(Sn),and lead(Pb)and known as carbon group

MNEMONIC for this group:

Chemistry Sir Gives Sanki Problems

Group 15 includes Nitrogen(N),Phosphorus(P),Arsenic(As),Antimony(Sb),and Bismuth(Bi) and known as nitrogen group.

MNEMONIC for this group:

Nahi Pasand Aise Sab Bhai

GROUP 16 contains Oxygen(O) sulphur (S), Selenium(S), Tellurium(Te), and Polonium(Po) and are these are known as oxygen group.

MNEMONIC for this group:

Oh! Style Se Tel Polish

Group 17 Fluorine (F), Chlorine(Cl),Bromine(Br),Iodine(I),and Astatine(At) and these groups are known as Halogens.

MNEMONIC for this group:
Fir Call Kar Bahaar AayI Aunty

Group 18 consist of Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn) and known group of noble gasses except Helium.

MNEMONIC for this Group:

He Never Arrived; Kara Xero Run pe Out Open / Comment

2021-06-10 15:44:06 F - block Tricks

Lanthanoides- Sar Par Nadiya Prem Ki Samayi, Yuu Gad-Gad Tab Dil Hua, Aree Tum Be Bhi Lutoge?

(Ce, pa, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

 
Actinides -Tumhe PadhaUUU Newspaper, Purane Aam Kam Bike(बिके) , Cafe me Aish Farmate Madonna Larra

(Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, La)

For More Scroll Up Wait For Next Post

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𝐉𝐎𝐈𝐍

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2021-06-09 17:27:17 Notes on s-Block Elements:

Covalent Character:.

Small cation and large anion favors covalency.

Order: LiCl > NaCl > KCl > RbCl > CsCl & . LiI > LiBr > LiCl > LiF

Greater the charge on the cation greater is its polarizing power and hence larger is the covalent character: Na+CI- < Mg+2CI2 < AI+3 CI3

Greater the charge on the anion, more easily it gets polarized thereby imparting more covalent character to the compound formed eg covalent character increase in the order. NaCI < Na2SO4 < Na3PO4

c) Lattice Energies: Amount of energy required to separate one mole of solid ionic compound into its gaseous ions.

Greater the lattice energy, higher is the melting point of the alkali metals halide and lower is its solubility in water

d) Hydration Energy: Amount of energy released when one mole of gaseous ions combine with water to form hydrated ions.

M+ (g) + aq → M+ (aq) + hydration energy

X- (g) + aq → X- (aq) + hydration energy

Higher the hydration energy of the ions greater is the solubility of the compound in water.

The solubility of the most of alkali metal halides except those of fluorides decreases on descending the group since the decrease in hydration energy is more than the corresponding decrease in the lattice energy.

Due to high hydration energy of Li+ ion, Lithium halides are soluble in water except LiF which is sparingly soluble due to its high lattice energy.

For the same alkali metal the melting point decreases in the order

fluoride > chloride > bromide > iodide

For the same halide ion, the melting point of lithium halides are lower than those of the corresponding sodium halides and thereafter they decrease as we move down the group from Na to Cs.

The low melting point of LiCl (887 K) as compared to NaCl is probably because LiCl is covalent in nature and NaCl is ionic.

Anomalous Behavior of Lithium and diagonal relationship with Magnesium:

Li has anomalous properties due to

Very small size

High polarizing Power

Lithium show diagonal relationship with magnesium because both elements have almost same polarizing power.

The melting point and boiling point of lithium are comparatively high.

Lithium is much harder than the other alkali metals. Magnesium is also hard metal.

Lithium reacts with oxygen least readily to form normal oxide whereas other alkali metals form peroxides and superoxides.

LiOH like Mg (OH)2 is weak base. Hydroxides of other alkali metals are strong bases.

Due to their appreciable covalent nature, the halides and alkyls of lithum and magnesium are soluble in organic solvents.

Unlike elements of group 1 but like magnesium. Lithium forms nitride with nitrogen.6Li + N2 → 2Li3N

LiCl is deliquescent and crystallizes as a hydrate, LiCI2H2O. Other alkali metals do not form hydrates. also forms hydrate, MgCI2.8H2O .

Unlike other alkali metals lithium reacts directly with carbon to form an ionic carbide. Magnesium also forms a similar carbide.

The carbonates, hydroxides and nitrates of lithium as well as magnesium decompose on heating.
Li2CO3 → Li2O + CO2

MgCO3 → MgO + CO2

2LiOH → Li2O + H2O

Mg (OH)2 → MgO + H2O

4LiNO3 → 2Li2O + 4NO2 + O2

2Mg ( NO3)2 → 2Mg + 4NO2 +O2

The corresponding salts of other alkali metals are stable towards heat.
Lithium nitrate, on heating, decomposes to give lithium oxide, Li2O whereas other alkali metals nitrate decomposes to give the corresponding nitrite.

4LiNO3 → 2Li2O + 4NO2 + O2

2NaNO3 → 2NaNO2 + O2

2KNO3 → 2KNO2 + O2

Li2CO3, LiOH, LiF and Li3PO4 are the only alkali metal salts which are insoluble in water. The corresponding magnesium compounds are also insoluble in water.

Hydrogen carbonates of both lithium and magnesium can not be isolated in solid state. Hydrogen carbonates of other alkali metals can be isolated in solid state.

Sodium Hydroxide (NaOH):
a. Properties

NaOH is stable towards heat but is reduced to metal when heated with carbon

2NaOH + 2C → 2Na +2CO + H2

FeCl3 + 3NaOH →Fe(OH)3 + 3NaCl

NH4Cl + NaOH → NaCl + NH3 (pungent smell) + H2O

@CRACK_BIOLOGY_101 Open / Comment

2021-06-09 15:33:30 BEST STRATEGY FOR 650+ MARKS IN 2 MONTHS

BY YOUR FAVOURITE SK SIR

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#neet_phodo_40_days_me Open / Comment

2021-06-09 15:23:17 Atoms & Molecules

Around 500 BC, an Indian Philosopher Maharishi Kanad, first time postulated the concept of indivisible part of matter and named it ‘pramanu.’

In 1808, John Dalton used the term ‘atom’ and postulated the atomic theory to the study of matter.


Dalton’s Atomic Theory
According to Dalton’s atomic theory, all matter, whether an element, a compound or a mixture is composed of small particles called atoms.
According to Dalton’s atomic theory, all matters, whether they are elements, compounds, or mixtures, are composed of small particles known as atoms.

Salient features of Dalton’s Atomic Theory
All matter is made of very miniscule particles known as atoms.
Atom is an indivisible particle, which cannot be created or destroyed through chemical reaction.
All atoms of an element are identical in mass and chemical properties whereas, atoms of different elements have different masses and chemical properties.
To form a compound, atoms are combined in the ratio of small whole numbers.
In a given compound, the relative number and kinds of atoms are constant.

Atomic Mass
The mass of an atom of a chemical element; it is expressed in atomic mass units (symbol is u).
The atomic mass is roughly equivalent to the number of protons and neutrons present in the atom.
One atomic mass unit is a mass unit equal to the exactly one-twelfth (1/12th) the mass of one atom of carbon-12 and the relative atomic masses of all elements have been calculated with respect to an atom of carbon-12.

Molecule
The smallest particle of an element or a compound, which is capable to exist independently and shows all the properties of the respective substance.
A molecule, normally, is a group of two or more atoms which are chemically bonded together.
Atoms of the same element or of different elements can join (with chemical bond) together to form molecules.
The number of atoms that constitute a molecule is known as its atomicity.

Ion
A charged particle is known as ion; it could be either negative charge or positive charge.
The positively charged ion is known as a ‘cation’.
The negatively charged ion is known as an ‘anion.’

Chemical Formulae
A chemical formula of a compound demonstrations its constituent elements and the number of atoms of each combining element.
The chemical formula of a compound is the symbolic representation of its Composition.
The combining capacity of an element is known as its ‘valency.’

Molecular Mass
The molecular mass of a substance is calculated by taking the sum of the atomic masses of all the atoms in a molecule of respective substance. For example, the molecular mass of water is calculated as −
Atomic mass of hydrogen = 1u
Atomic mass of oxygen = 16 u

The water contains two atoms of hydrogen and one atom of oxygen.
Molecular Mass of Water is = 2 × 1+ 1×16 = 18 u (u is the symbol of molecular mass).

Formula Unit Mass
The formula unit mass of a substance is calculated by taking the sum of the atomic masses of all atoms in a formula unit of a compound.

Avogadro Constant or Avogadro Number
Avogadro was an Italian scientist who had given the concept of Avogadro Number (also known as Avogadro Constant).
The number of particles (atoms, molecules, or ions) present in 1 mole of any substance is fixed, and its value always calculated as 6.022 × 1023.
In 1896, Wilhelm Ostwald had introduced the concept of ‘mole;’ however, mole unit was accepted to provide a simple way of reporting a large number in 1967.

Law of Conservation of Mass
During a chemical reaction, sum of the masses of the reactants and products remains unchanged, which is known as the ‘Law of Conservation of Mass.’

Law of Definite Proportions
In a pure chemical compound, its elements are always present in a definite proportion by mass, which is known as the ‘Law of Definite Proportions.’


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𝐉𝐎𝐈𝐍

​▒☞@crack_biology_101 Open / Comment

2021-06-09 14:30:19 NEET-2021 Crack करना है लेकिन Confidence नही आ रहा, समय है कम, अब क्या करे

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Open / Comment

2021-06-08 20:17:14 Useful activities

(i) Decay of organic wastes: Many saprotrophic bacteria act as natural scavengers by continuously removing the harmful organic wastes (i.e., dead remains of animals and plants) from man's environment. They decompose the organic matter by putrifaction and decay. The simple compounds produced as a result of decomposition and decay (viz., carbon dioxide, carbon monoxide, nitrates, sulphates, phosphates, ammonia, etc.) are either released back into the environment for recycling or absorbed by the plants as food. Thus, the bacteria play duel role by disposing of the dead bodies and wastes of organisms and by increasing the fertility of soil.

(ii) Role in improving soil fertility: Saprotrophic bacteria present in soil perform various activities for their survival. Some of these activities improve the fertility of soil by formation of humus, manure, etc.

(a) Humus: The microbial decomposition of organic matter and mineralization results in the formation of complex amorphous substance called humus. The humus improves the aeration, water holding capacity, solubility of soil minerals, oxidation-reduction potential and buffering capacity of the soil.

(b) Composting: It is conversion of farm refuse, dung and other organic wastes into manure by the activity of saprotrophic bacteria (e.g., Bacillus stearothermophilus, Clostridium thermocellum, Thermomonospora spp, etc.)

(c) Adding sulphates: A few sulphur bacteria (e.g., Beggiatoa) add sulphur into the soil by converting H2S into sulphates.

(iii) Sewage, disposal: Ability of anaerobic bacteria to purify the organic matter is used in the the sewage disposal system of cities. The faeces are stored in covered reservoirs and allowed to purify. The solid matter is decomposed into liquidy sludge which is passed through coarse filters. The effluent is finally purified and drained out into the river or used as fertilizer in the fields. The common bacteria involved in sewage disposal are – Coliforms (E. coli), Streptococci, Clostridium, Micrococcus, Proteus, Pseudomonas, Lactobacillus, etc.

(iv) Role in Industry: Useful activities of various bacteria are employed in the production of a number of industrial products. Some of these are given below–

(a) Lactic acid: Lactic acid is commercially produced from pasteurized whey (the watery part of milk) through fermentation caused by Lactobacilus bulgaricus and L. delbrueckii.

(b) Curd: Curd is prepared from pasteurized milk by the process called curdling. It is initiated by adding a starter culture of Lactobacillus bulgaricus and Streptococcus thermophillus, into the milk at 40°C. Lactobacillus converts lactose to lactic acid whereas Streptococcus causes coagulation of casein due to acidity.

(c) Cheese: Preparation of cheese from the milk involves two main steps – first curdling of milk, and second the subsequent ripening of solid curd by the use of different bacterial strains.

(d) Butter: It is prepared by churning of sweet or sour cream. The microorganisms responsible for preparation of butter cream are – Streptococcus lactis and Leuconostoc citrivorumare. The characteristic butter aroma develops due to a volatile substance – diacetyl. It is produced by the action of streptococcus on pasteurized milk.

(e) Retting process: Fibres of flax, hemp and jute are separated by the process called retting. During this process the stems of the plants are submerged in water, where the bacterial activity results in the rotting of softer parts. The tough bast fibres become loosened and easily separated from each other. These fibres are spun and woven into various articles.


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2021-06-08 07:24:32 Tricks for Conversions in Organic Chemistry

Haloalkanes can give you every possible functional group. They can also help you in increasing the chain size. So you might want to convert your starting material to haloalkanes and then go to the desired product

Remember the series of oxidation/reduction: Hydrocarbons (with various substituents) can be oxidised to alcohols, then appropriate carbonyl compounds and lastly carboxylic acids (or their derivatives)

Strong oxidizing agents are KMnO4 and K2Cr2O7

Mild oxidising agents depending on the situation are CrO4, Ammoniacal AgNO3, Benedicts Solution, Fehling’s solution, Cu or CuO at 573K, Bromine water etc.

Any carboxylic acid derivative can be converted back to the carboxylic acid by hydrolysis.

There are possibilities of hydride and methyl to get the most stable intermediate (carbocation/free radical)

A most common reaction, if your starting material is an alkane, is free-radical halogenation.

Saytzeff/Markovnikov's rules must be kept in mind while dealing with alkenes (they are based on the electron displacement effects only)

Decarboxylation and ozonolysis could go-to methods for decreasing the number of carbon atoms

Grignard reagent gives you the much-needed Alkyl nucleophile, which can be used at appropriate places.

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