CHEMISTY IN EVERYDAY LIFE NOTES

                          CHEMISTY IN EVERYDAY LIFE

➱ Drugs : Drugs are the chemical substances of low molecular mas, interact with macromolecular targets and produce a biological response.
➱ Medicines : Drugs which produce a therapeutic and useful response.
➱ Chemotherapy : It is the science in which chemicals are used in the treatment of diseases due to bacterial invasion.These chemicals destroy the micro-organisms without affecting any material extent, the tissues of the host).
➱ Classification of Drugs :
(i) On the basis of pharmacological effect : Most useful for doctors as it provides the whole range of drugs available for the treatment of a particular type of problem. e.g., analgesics have pain killing effect, antiseptics kill or arrest the growth of microorganisms.
(ii) On the basis of drug action : It is based on the action of a drug on a particular biochemical process. e.g., all histamines inhibit the action of the compound histamines, which causes inflammation of the body.
(iii) On the basis of chemical structure : Drugs which have common structural features and often have similar pharmacological activity. e.g., sulphonamides have common structural feature.

Class xii Solution Online MCQ Test

XII Solutions ONLINE MCQ QUIZ

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XI Unit IX: Hydrogen

Position of hydrogen in periodic table, occurrence, isotopes, preparation, properties and uses of hydrogen, hydrides-ionic covalent and interstitial; physical and chemical properties of water, heavy water, hydrogen peroxide -preparation, reactions and structure and use; hydrogen as a fuel.

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Study Material:

NCERT   NIOS

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Previous year question:

• CBSE
• BSEB
• Maharashtra Higher Secondary Education
• Uttar Pradesh Madhyamik Shiksha Parishad
• WBCHSE
• Directorate of Government Examinations Tamil Nadu
• Board of Secondary Education, Madhya Pradesh
• Karnataka Department of Pre-University Education
• JEE
• NEET
•  

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ANIMATIONS 

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Online MCQ Test 

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XI Unit V: States of Matter: Gases and Liquids

Three states of matter, intermolecular interactions, types of bonding, melting and boiling points, role of gas laws in elucidating the concept of the molecule, Boyle's law, Charles law, Gay Lussac's law, Avogadro's law, ideal behaviour, empirical derivation of gas equation, Avogadro's number, ideal gas equation. Deviation from ideal behaviour, liquefaction of gases, critical temperature, kinetic energy and molecular speeds (elementary idea)Liquid State- vapour pressure, viscosity and surface tension (qualitative idea only, no mathematical derivations)

................................................................................................................................................................

Study Material:

NCERT   NIOS

................................................................................................................................................................

Previous year question:

• CBSE
• BSEB
• Maharashtra Higher Secondary Education
• Uttar Pradesh Madhyamik Shiksha Parishad
• WBCHSE
• Directorate of Government Examinations Tamil Nadu
• Board of Secondary Education, Madhya Pradesh
• Karnataka Department of Pre-University Education
• JEE
• NEET
•  

................................................................................................................................................................

ANIMATIONS 

................................................................................................................................................................

Online MCQ Test 

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Avogadro's Hypothesis and Its Applications

1 Development of Avogardro's hypothesis

2 Definition of Avogadro's hypothesis

3 Application of Avogadro's hypothesis

i. Deduction of atomicity of elementary gas

ii. Deduction of relationship between molecular mass and vapour density

iii. Deduction of molar volume of gases

iv. Deduction of molecular formula from its volumetric composition

(Solving related numerical problems)

Empirical, Molecular Formula and Limiting Reagents

Percentage compositions

Derivation of empirical and molecular formula from percentage composition

Chemical calculation based on following chemical equation

- Limiting reactants

- Mass-mass relationship

- Volume – volume relationship

- Mass volume relationship

(Solving reacted numerical problems)

Mole in term of mass, volume number and ions

Calculation based on mole concept

Mole concept

Definition of atomic mass and molecular mass

Law of Constant Proportion

Law of multiple proportions

Law of reciprocal proportions

Law of gaseous volumes

Chemical calculations based on stoichiometry

https://chem-guide.blogspot.com/2010/03/chemical-calculations-based-on.html

Law of conservation of mass

https://chem-guide.blogspot.com/2010/03/law-of-conservation-of-mass.html

Dalton's atomic theory

Dalton's atomic theory and Laws of Stoichiometry

Green house effect

https://chem-guide.blogspot.com/2010/04/green-house-effect.html

Acid rain, water pollution

https://chem-guide.blogspot.com/2010/04/acid-rain-water-pollution.html

Air pollution, photochemical smog

Applications of hydrogen

The main uses are in the petroleum industry and in making ammonia by the Haber process. Some is used elsewhere in the chemical industry. A little of it is used as fuel, for example in rockets for spacecraft. Most of the hydrogen that people use comes from a chemical reaction between natural gas and steam.

Nuclear fusion

Nuclear fusion is a very powerful source of energy. It relies on forcing atoms together to make helium and energy, exactly as happens in a star like the Sun, or in a hydrogen bomb. This needs a large amount of energy to get started, and is not easy to do yet. A big advantage over nuclear fission, which is used in today's nuclear power stations, is that it makes less nuclear waste and does not use a toxic and rare fuel like uranium. More than 600 million tons of hydrogen undergo fusion every second on the Sun.

Burning Hydrogen

The electrolysis of water easily breaks water into hydrogen and oxygen, using electricity. Burning hydrogen combines with oxygen molecules to make steam (pure water vapor). A fuel cell combines hydrogen with an oxygen molecule, releasing an electron as electricity. For these reasons, many people believe hydrogen power will eventually replace other synthetic fuels.
Hydrogen can also be used as fuel in a fuel cell, or burned to make heat for steam turbines or internal combustion engines. Hydrogen can be created from many sources such as coal, natural gas or electricity, and therefore represents a valuable addition to the power grid; in the same role as natural gas. Such a grid and infrastructure with fuel cell vehicles is now planned by a number of countries including Japan, Korea and many European countries. This allows these countries to buy less petroleum, which is an economic advantage. The other advantage is that used in a fuel cell or burned in a combustion engine or turbine, there is no pollution. Only water, and a small amount of nitrogen oxides, forms.

Ortho and Para hydrogen

A molecule of dihydrogen contains two atoms, in which the nuclei of both the atoms are spinning. Depending upon the direction of the spin of the nuclei, the hydrogens are of two types:

Ortho hydrogen molecules are those in which the spins of both the nuclei are in the same direction.

Molecules of hydrogen in which the spins of both the nuclei are in the opposite direction are called para hydrogen.

Fig: 11.2 - Ortho and para hydrogen

Ordinary dihydrogen is an equilibrium mixture of ortho and para hydrogen.

from wikipedia

The amount of ortho and para hydrogen varies with temperature as:

At 0°K, hydrogen contains mainly para hydrogen which is more stable.

At the temperature of liquefaction of air, the ratio of ortho and para hydrogen is 1 : 1.

At the room temperature, the ratio of ortho to para hydrogen is 3 : 1.

Even at very high temperatures, the ratio of ortho to para hydrogen can never be more than 3 : 1.

Thus, it has been possible to get pure para hydrogen by cooling ordinary hydrogen gas to a very low temperature (close to 20 K) but it is never possible to get a sample of hydrogen containing more than 75% of ortho hydrogen.

Isotopes of hydrogen

Hydrogen is the most abundant element in the universe. About half the mass of sun and stars is due to hydrogen. Jupiter and Saturn planets consist mainly of hydrogen. It is common on earth in water, coal, petroleum, clay, animal and vegetable matter that constitutes 0.9% by weight of Earth's crust. It is the ninth element in order of abundance.

Isotopes of hydrogen

Isotopes are the different forms of the same element, which have the same atomic number but different mass numbers. The isotopes of hydrogen are protium, deuterium and tritium with mass number 1, 2 and 3 respectively. The relative abundance of three isotopes in nature is in the ratio of 1 : 1.5 x 10^-2: 1 x 10^-17respectively. The hydrogen occurring in nature is mainly composed of atoms of protium and it contains only 0.015% of deuterium atoms. The third isotope of hydrogen is radioactive.

All the three isotopes of hydrogen have one electron in their only shell and one proton in the nucleus. However, they differ with respect to the number of neutrons in them.

It is the most abundant isotope of hydrogen. Its nucleus has one proton and no neutron (mass number = 1). It is represented as H.

It is present in heavy water (D₂O) and can be recovered by fractional electrolysis. Its nucleus has one proton and one neutron (mass number = 2). It is represented as D.

Tritium

It is the rarest isotope of hydrogen (10^-15%) due to the instability and radioactive nature of its nucleus. Its nucleus has one proton and two neutrons (mass number = 3). It is represented as T. It is prepared artificially, by the bombardment of nitrogen and an isotope of lithium with deutrons.

Atomic hydrogen , Nascent hydrogen

Atomic Hydrogen

Langmuir ,in 1915, obtained atomic hydrogen by dissociating on a hot filament of tungsten or platinum. The dissociation of molecular hydrogen is an endothermic process.

The atomic hydrogen is stable only for a fraction of a second and immediately reverts back to its molecular form, liberating a large amount of energy.

Atomic hydrogen is extremely reactive, being more reactive than ordinary, nascent, or adsorbed oxygen. When it is passed over metals or non-metals, it forms hydrides at normal temperatures, excepting for nitrogen, to which it does not react.

Atomic hydrogen is an extremely powerful reducing agent, reducing oxides chlorides and sulphides of some metals like Ag, Hg, Cu etc. to metals at ordinary temperature.

Nascent Hydrogen

The hydrogen gas, which is just liberated as a result of a chemical is called nascent hydrogen or newly born hydrogen. It is obtained by passing dihydrogen gas at atmospheric pressure through an electric arc between two tungsten rods. The electric arc maintains a temperature around 4000 - 4500°C. As the molecules of dihydrogen gas pass through the electric arc, these absorb energy and get dissociated into atoms as nascent hydrogen. It is more reactive than ordinary hydrogen and its colour is not discharged. (pink in colour). For example, if ordinary hydrogen is passed through acidified KMnO₄ it does not get decolourised. However, if zinc pieces are added to the same solution, bubbles of hydrogen rise up through the solution and the colour is discharged due to the reduction of KMnO₄ by nascent hydrogen.

Position of hydrogen in periodic table

Hydrogen is the first element of the periodic table. Its atomic number is 1, which indicates the presence of only one electron in the atom of hydrogen. This electron is present in its first shell. Hydrogen resembles both alkali metals (group I A) as well as halogens (group VII A) therefore its position is said to be anomalous.

Some Basic Features of Hydrogen

Symbol	H
Molecular formula	H2
Atomic number	1
Mass number	1
Atomic mass	1.008
Molecular mass	2
Electronic configuration	1
Valency	+ 1 or - 1
Isotopes of Hydrogen	11H Protium
	21H Deuterium
	31H Tritium

Remember :

Isotopes are atoms of the same element having the same atomic number, but different mass number.

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Properties of Hydrogen that Resemble Alkali Metals

Electronic configuration

Hydrogen atom has one electron in its valence shell like alkali metals.

Valency

Hydrogen generally shows + 1 valency like alkali metals.

Metallic character

It readily loses its electron to form a positive ion like other alkali metals.

Combination with non-metals

Hydrogen, like the alkali metals, combines readily with non-metals like halogens, oxygen, sulphur, etc.

Reducing agent

Hydrogen is a good reducing agent like other alkali metals.

Properties of Hydrogen that Resemble Halogens

Non-metallic character

Hydrogen is a non-metal like halogens.

Atomicity

Like halogens, hydrogen is diatomic (H₂) whereas metals are monoatomic.

Valency

Like halogens, hydrogen may also show 1 valency by accepting an electron. Example: NaH (Sodium hydride)

Nature of compounds

Hydrogen combines with non-metals like carbon, silicon, etc. to from covalent compound like halogens.

Examples: CH₄ and CCl₄.

Remember :

In 1766, Henry Cavendish, an English chemist, discovered hydrogen, by treating iron with dilute sulphuric acid. He also proved that when hydrogen is burnt in air, water is the only product obtained. It was "hydrogen", meaning "water producer" (Hydro = water,

gen = generator or producer). Cavendish called this gas "Inflammable gas". Hydrogen has three isotopes namely protium, deuterium and tritium.