Agriculture Exams Library

2021-03-31 19:38:22 Atoms & Molecules
#Chemistry #FCI

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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2021-03-31 05:53:33 #seed Open / Comment

2021-03-31 05:03:18 Radioactivity
#Important_topic
#chemistry #FCI
The process of emission of particles from nuclei because of the nuclear instability; is known as radioactivity.
The substance that releases such energy/rays is known as radioactive substance.
The invisible rays released from such radioactive substance are known as radioactive rays.
Likewise, radioactivity is a nuclear phenomenon that happens (naturally) because of the nuclear instability of atoms.
In 1896 Henri Becquerel first observed the phenomena of radioactivity, but the term ‘radioactivity’ was coined by Marie Curie.
Marie Curie discovered the radioactive elements namely Polonium and Radium in 1898.
For her discovery, Marie Curie won the Nobel Prize.


Radioactive Rays
After long years of experiment, Ernest Rutherford along with his colleague (Hans Geiger and his student Ernest Marsden), discovered alpha rays, beta rays, and gamma rays.
These rays emitted as the result of the disintegration of atoms.


Alpha (α) Particles
Alpha particles are usually composed of two protons and two neutrons, which are tightly bound together.
Alpha particles are being released during radioactive decay (or alpha decay) from the nucleus radio nuclides.
The alpha particles are identical to the nucleus of either normal helium atom or doubly ionized helium atom.
In comparison to other particles (i.e. Gamma and Beta), alpha particles are heavy and slow. Therefore, alpha particles have very small range in the air.
Because of slow speed, Alpha particles have very weak penetrating powers; these particles are even stopped by a thin paper sheet (see image given above).
Because of having the double positive charge, alpha particles are highly ionizing.


Beta (β) Particles
Beta particles are the fast moving electrons emitted by some radio nuclides during the radioactive decay (also known as beta decay).
Beta particles are of much lighter weight and carry a single negative charge.
Beta particles are rarely ionizing than the alpha particles.
Because of having lighter weight, beta particles can travel much farther than alpha particles; however, beta particles can be stopped by several sheet of papers or one sheet of aluminum.
Beta particles are negatively charged and get attracted towards positively charged particles.


Gamma (ү) Particles
Gamma particles are the bundle of high energy namely electromagnetic energy (photon) emitted by the radioactive elements during the radioactive decay.
Among all three particles (alpha, beta, and gamma), gamma particles are the most energetic photons.
Gamma particles, which are the form of electromagnetic radiation(EMR), originate from the nucleus.
The wavelengths of gamma are the shortest among all three.
Gamma particles have no charge and they are neutral; therefore, they are unaffected by magnetic and electric fields.


Uses of Radioactive Elements
Medical field (treatment of many diseases)
Industrial process
Energy production – Nuclear reactors
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2021-03-29 14:08:03 Notes on Chemical Bonding For #FCI Exam #Chemistry

Chemical bond:-
Chemical bond is the attractive force which holds various constituents together in a molecule.

There are three types of chemical bonds: Ionic Bond, Covalent Bond, Co-ordinate Bond.

Octet Rule:
Atoms form chemical bonds in order to complete their octet i.e. eight electrons in their valence shell.

Lewis Structures:
Pair of bonded electrons is by means of a ‘dash’ (-) usually called a ‘bond’.

Lone pairs or ‘non-bonded’ electrons are represented by ‘dots’.

Electrons present in the last shell of atoms are called valence electrons.

Exceptions to the Octet Rule:
Species with odd number of electrons: NO, NO2,

Incomplete octet for the central atom: LiCl, BeH2 and BCl3

Expanded octet for the central atom: PF5, SF6 and H2SO4

Formal Charge:
Formal charge is the difference between the number of valence electrons in an isolated atom and number of electrons assigned to that atoms in Lewis structure.

Formal charge = [Total number of valence electrons in the free atom ) - (Total number of lone pairs of electrons) -1/2(Total number of shared electrons i.e. bonding electrons)]

Resonance:
For molecules and ions showing resonance it is not possible to draw a single Lewis structure.

All the properties of such species can only be explained by two or more Lewis structures. Example: Resonance of O3

Ionic Bonding:
Formation of Ionic Bond:
Formation of ionic bond takes place between a metal and a non-metal by transfer of electron.

Formation of gaseous cations

A(g) + I.E. → A+ (g) + e

Ionization Energy

Formation of gaseous anions

X(g) + e → X- (g) + E.A

Electron Affinity

Packing of ions of opposite charges to form ionic solids

A+ (g) + X- (g) →AX (s) +Energy

Lattice energy

Conditions required of formation of ionic bonds:

Low I.E of cation.

High E.A of anion.

High lattice energy.

Covalent Bonding:
Covalent bond is formed between two non-metals by sharing of electrons.

Electron pairs which participate in bonding are called bond pairs.

Electron pairs which do not participate in bonding are called lone pairs.

There could be single, double or triple covalent bonds between two elements depending on the number of electrons being shared.

VSEPR (Valence Shell Electron Pair Repulsion) Theory:
The shape of the molecule is determined by repulsions between all of the electron pairs present in the valence shell.

Order of the repulsion: Lone pair Lone pair > Lone pair Bond pair > Bond pair Bond pair.

Repulsion among the bond pairs is directly proportional to the bond order and electronegativity difference between the central atom and the other atoms.
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2021-03-29 10:14:13 #FCI #AFO #NABARD
Respiratory quotient:

R.Q. is the ratio of the volume of CO2 released to the volume of O2
absorbed in the respiration.

It is also called respiratory ratio.

R.Q.= volume of released CO2 /Volume of absorbed O2.

R.Q. values of some products:
Succulents: 0
Fat: 0.7
Protein: 0.8-0.9
Carbohydrates: 1.0
Organic acid: >1 or 1.33 Open / Comment

2021-03-29 05:18:11 Launch of Pradhan Mantri Matsya Sampada Yojana

The Pradhan Mantri Matsya Sampada Yojana (PMMSY) is a flagship scheme for focused and sustainable development of fisheries sector in the country with an estimated investment of Rs. 20,050 crores for its implementation during a period of 5 years from FY 2020-21 to FY 2024-25 in all States/Union Territories,as a part of AatmaNirbhar Bharat Package.

Out of this, an investment of about Rs 12340 crores is proposed for beneficiary-oriented activities in
Marine, Inland fisheries and Aquaculture and about Rs 7710 crores investment for Fisheries
Infrastructure.

PMMSY aims at enhancing fish production by an additional 70 lakh tonne by 2024-25, increasing
fisheries export earnings to Rs.1,00,000 crore by 2024-25, doubling of incomes of fishers and fish
farmers, reducing post-harvest losses from 20-25% to about 10% and generation of additional 55 lakhs direct and indirect gainful employment opportunities in fisheries sector and allied activities.

PMMSY scheme primarily focuses on adopting ‘Cluster or Area based approaches’ and creation of
Fisheries clusters through backward and forward linkages.

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2021-03-28 11:37:56 #Growth_Hormone Open / Comment

2021-03-28 06:19:04 Important Horticultural institute

Central Institute forr Subtropical Horticulture- Lucknow

Central Institute of Temperate Horticulture- Srinagar

Central Tuber Crops Research Institute- Thiruvananthapuram

Central Plantation Crops Research Institute- Kassargod

Central Potato Research Institute- Kufri

Indian Institute of Horticultural Research- Bangalore

Indian Institute of Spices Research- Calicut

Central Institute for Arid Horticulture- Bikaner

Central Research Institute for Chikoo- Muzaffarpur

National Research Center for Banana- Tiruchirapalli

National Research Center for Cashew- Puttur

National Research Center for Citrus- Nagpur

National Research Center for Grapes- Pune

Directorate of Mushroom Research- Solon

National Research Center for Medicinal & Aromatic Plants- Anand

National Research Center for Onion & Garlic- Nasik

National Research Center for Orchids- Gangtok

National Research Center for Seed Spices- Ajmer

Indian Institute of Vegetable Research- Varanasi

National Horticultural Board- Gurgaon

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2021-03-27 09:46:40 FUNCTIONS OF NUTRIENTS

• C, H and O are the elements that provide basic structure to the plant.

• N, S and P are useful in energy storage, transfer and bonding.

• N, S and P are accessory structural elements which are more active and vital for living tissues.

• K, Ca and Mg are necessary for charge balance. They act as regulators and carriers.

• Fe, Mn, Zn, Cu, B, Mo and Cl are involved in enzyme activation and electron transport. They act as catalysers and activators.

• Basic nutrients C, H and O are constituents of carbohydrates and several biochemical compounds.

• Nitrogen is a constituent of proteins, enzymes, hormones,
vitamins, alkaloids, chlorophyll etc.

• Phosphorus is a constituent of sugar phosphates, nucleotides, nucleic acids, coenzymes and phospholipids.

• Process of anabolism and catabolism of carbohydrates proceed when organic compounds are esterised with phosphoric acid.

• Potassium is not a constituent of any organic compound.

• Potassium is required as a cofactor for 40 or more enzymes.

• Potassium controls movement of stomata and maintains electroneutrality of plant cells.

• Sulphur is a constituent of several aminoacids and fatty acids.

• Calcium is a constituent of cell wall as calcium pectate.

• Calcium is required as a cofactor in hydrolysis of ATP and phospholipids.

• Magnesium is a constituent of chlorophyll.

• Magnesium is required in several enzymes involved in phosphate transfer.

• Iron is a constituent of various enzymes like cytochrome,
catalase and plays the part of a vital catalyst in the plant.

• Iron is a key element in various redox reactions of respiration, photosynthesis and reduction of nitrates and sulphates.


• Manganese is a constituent of several cation activated enzymes like decarboxylases, kinases, oxidases etc.

• Manganese is essential for the formation of chlorophyll,
reduction of nitrates and for respiration.

• Copper and Zinc are involved in cation activated enzymes.

• Boron helps in carbohydrate transport.

• Boron is necessary for the germination of pollen, formation of flowers and fruits and for the absorption of cations.

• Molybdenum is required for the assimilation of nitrates as well as for the fixation of atmospheric nitrogen.

• Chlorine is involved in reaction relating to oxygen evolution.

• Co, Se are the elements that need to be applied to forage crops from the viewpoint of animal nutrition.

• Cobalt is essential for the synthesis of vitamin B12.**

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