Class 11 chemistry ch 9

Class 11 chemistry chapter 9

CBSE Class 11 Chemistry Notes : Hydrogen

It was discovered by Henry Cavendish in 1766 by the action of dilute H2O4 on iron. It was named ‘inflammable air’, Lavoisier gave it the name hydrogen (Creek: Hydra = water, gennas = producer]. It occurs in free state as well as in combined state.

Position of Hydrogen in the Periodic Table

Hydrogen resembles with alkali metals (group I) as well as halogens (group 17), At the same time, it differs from both in certain characteristics. That is why hydrogen if; called “rogue element”.

However. it has been placed in group 1 on the basis of its configuration 1s1, which is the basis of modern classification of elements.

Isotopes of Hydrogen

Hydrogen exists in the form of three sotopes :

Dihdrogen [H2]

Methods of Preparation

(a) Lab pletbods

Metals which have reduction potential lesser than H, can liberate H2 from acids.

Pure zinc is not used because it reacts slowly. The presence of some impurities increases the rate of reaction due to the

formation of electrochemical couples Cone sulphuric acid is also not used because it oxidises, H2 formed into H2O.

Zn + 2H2SO4(conc.) → ZnSO4 + SO2 + 2H2O

(ii) It can also be prepared by the reaction of zinc with aqueous alkali.

b) Commercial production of dihydrogen

(i) By the electrolysis of acidified water

ii) From water gas (Bosch process)

Carbon dioxide is removed by dissolving it in water under pressure (20-25 atm) and hydrogen left behind is collected.

(iii) From steam (Lane’s process) Super heated steam is passed over iron filings heated to about 1023-1073 K when hydrogen is

formed.

(iv) Highly pure (> 99.95%)dihydrogen is obtained by electrolysing warm aqueous barium hydroxide solution between nickel

electrodes. (V) Hydrocarbons with partial oxidation

 6) It is also obtained as a product of NaOH chlorine in salt electrolysis.

 Reactions occur during electrolysis

 Physical properties of Rogen hydrogen

 Dihydrogen is a colorless, fragrant, tasteless, flammable gas.  The air is light and insoluble in water.  Lakmus is neutral.

 Chemical properties of Rogen hydrogen

 (I) Reaction The relative inertia of the dihydrogen at room temperature is due to the high ethalpi of the H-H bond, ie the high dissociation energy of the bond.  Therefore, its reactions take place only under special conditions (high temperature).

 (Ii) Working with non-metals

 (3) Interaction with H2 minerals acts as an oxidizing agent.

 (4) Reduction of hydrogen action

 (v) Interaction with metal ions and metal oxides

 (6) Interaction with organic compounds

 Use of dihydrogen

 It is used in the production of CH3OH.

 It produces a temperature of 2850 ° C, and the hydrogen flame generates 4000 ° C of atomic oxygen, so it is used in oxygen and hydrogen fire.

 The only major use of H2 is in the synthesis of NH3, which is used in the production of HNO3: fertilizers.

 Liquid hydrogen (LH2) is used as rocket fuel.

 H2 is used as a reducing agent in the extraction of minerals.

 H2 is used in the fuel cell to generate electricity.

 Rogen hydrogen is used in the production of synthetic gasoline.

 (Heating with coal and heavy oils by heating H2 under the presence of a catalyst under very high pressure).

 Different types of Rogen hydrogen

 Atomic hydrogen

 It is very interactive and has a half-life of 0.33 seconds.

 Dirty hydrogen

 Newly prepared hydrogen is known as newborn hydrogen and is more reactive than regular hydrogen.  This causes some compounds to shrink and is not possible with normal hydrogen.  It can never be isolated.

 The activity of the newborn H depends on the response through which it is acquired.

 Hyd hydrogen is absorbed

 The absorption of Rogen hydrogen on the metal surface is called blocking.  This hydrogen undergoes many chemical changes, such as reduction and hydrogen.  The blockage decreases as the temperature rises.

 Orthophora hydrogen

 When in a hydrogen molecule, the nuclear windings rotate in the same direction as the orthodontic hydrogen.  On the other hand, when the nuclear rotation rotates in the opposite direction.  Hydrogen Para is known.  Rogen hydrogen at room temperature consists of 75% ortho և 25% para hydrogen.

 Hydrogen crop economy

 Hyd hydrogen is the use of liquid hydrogen as an alternative energy source.  The technology includes energy production, transmission and storage of liquid hydrogen.  Hyd hydrogen can be widely produced by electrolysis of water or by a chemical-thermal reaction cycle.  Hyd hydrogen can be stored in liquid form in vacuum, metal or all alloys, such as titanium alloys and iron, as inter-parliamentary hyde, in refrigerated tanks.  Hydrogen fossil fuels have many advantages over conventional fuels in that they are not polluted and release a lot of energy during combustion.

 Pbotohydrogen is used to get renewable energy from the sun by using microorganisms such as bacteria or algae.

 R

 Hydrogen compounds with minerals and non-metals are called hydrides.

 Hydride ion

 It consists of elements of the first and second groups (except for Be և Mg), heating them in hydrogen.

 These are white colorless (crystalline) solids that have a high PP content.  And St.  Easily decomposes with water, CO2 or SO2.

 CaH2 + 2H2O → Ca (OH) 2 + 2H2

 CaH2 + 2CO2 → (HCOO) 2Ca:

 They are reinforcing agents.  Alkali metal hydrates are used to make LiAlH4, NaBH4, etc. and to remove traces of water from organic compounds.

 Molecular or covalent hydrates

 These are made up of P-mass elements that have a higher electronegativity than hydrogen.

 These insufficient electronic hydrates are hydrates that do not have enough electrons to form normal covalent bonds, such as BH3, AlH3, and so on.

 To you  

Precision electron hydride These hydrates have the exact number of electrons needed to form normal covalent bonds.  For example, fourteenth group hydrides (CH4, SiH4, etc.)

 Electron-rich hydrates, which are hydrates that contain more electrons than are required to form normal covalent bonds.  day.  Hybrid groups 15, 16, 17 (NH3, PH3, H2S, HF, HCl, etc.).  In this hybrid, the extra electrons are present as one pair of electrons.

 Metal or interstate hydrate

 Transitional and rare earth minerals combine with hydrogen from interstellar hydrates.  Mineral properties appear and are strong reducing agents.  They are asymmetric hydrates, and their composition varies with temperature and pressure, for example, LaH2.76, TiH1.73.

 Minerals 7, 8 և 9 do not form hydrate, այս This periodic table is called a hydride gap.

 Polymeric hydrates and complex hydrides

 Polymeric hydrates are composed of elements having a electrode of 1.4 to 2.0, for example (BeH2) n, (AlH3) n և etc.  In complex hydrates, H acts as the ligand: linked to the central metal seed, such as LiAlH4, LiBH4, and so on.

 Where?

 Water is the most common and widespread on Earth.  It occurs in all three physical situations.  H2O is a covalent molecule where oxygen is hybridized with sp3.  It has an inclined structure.

 Physical properties of physical

 As there is a colorless, fragrant, tasteless liquid.  Abnormally high temperature, evaporative heat due to hydroelectric connection.

 Pure water is not a good conductor, so it is made by transferring a small amount of acid or alkali.

 The density of ice (which is the mass of one unit) is less than the amount of water floating on the water.

 It has a maximum density of 4 ° 0.

 Water is a high-load solution with a high dielectric constant of 78.39.  It interacts effectively with polar or ionic materials, and releases large amounts of energy due to the interaction of the ionic dipole.  The decomposition of covalent compounds such as uranium, glucose, C2H5OH, etc., is due to the tendency of these molecules to form hydrogen bonds with water.

 Chemical properties of chemicals

 1. The water is naturally oscillating.

 2. In oxidation and reduction reactions, water interacts with both minerals and non-minerals.

 3. In the case of aqueous salts, the water can be of five types: systemic water, hydrogen-related water, network water, multiply water and zeolite water.

 4. A number of compounds such as calcium hydrite and calcium phosphide.  Etc. and so on.  Hydrolysis.

 Pure cleaning

 It involves two processes

 Removing suspended waste water

 Destruction of bacteria.

 The suspended particles are removed by coagulation with aluminum, followed by filtration.

 The effects of sunlight, boiling, chlorine (treatment with liquid Cl2 or bleaching powder), ozone, and CuSO5 addition are some of the processes used to kill bacteria.

 Heavy water [D2O]

 It was discovered by Urr in 1932. It can be prepared using regular water-soluble electrolysis using nickel electrodes.  It is colorless, odorless and tasteless liquid.

 Chemical reactions of heavy water

 Use heavy water

 They are used

 To slow the speed of neutrons in nuclear reactors, they are called intermediaries.

 As a tracking compound to study the mechanisms of multiple interactions.

 Hard and hard water

 Urea, which produces a large amount of soap, is known as soft water, which produces soap scrub, known as hard water.

 Types of hardness

 Temporary hardness due to the presence of calcium and magnesium bicarbonate.

 Constant hardness Tt due to the presence of calcium, magnesium, and sulfate chlorides.

 Temporary hardness removal

 Achievable.

 A) By boiling, the soluble bicarbonate is converted into insoluble carbonate.

 B) The clarity process by adding lime water or lime milk.

 Removing permanent hardness

 I) By adding baking soda, calcium or magnesium salts are deposited in the form of carbonate.

 (ii) By adding caustic soda The temporary and permanent hardness can be removed by adding caustic soda.

(iii) By adding sodium phosphate (Na3PO4) The phosphates of calcium and magnesium are precipitated.

Similarly, magnesium also precipitate out in the form of magnesium phosphate, Mg3(PO4)2.

(iv) Calgon’s process Calgon is sodium hexa metaphosphate (Na6P6O18). This calgon when added to hard water form soluble complex.

Similarly. Mg2+ can also precipitate as Na2[Mg2(PO3)6] and water becomes free from Ca2+ and Mg2+ Ions.

(v) Permutit process Permutit is hydrated sodium aluminium silicate Na2Al2Si2O8.xH2O. It exchanges its sodium ions for divalent ions Ca2+ and Mg2+..

Permutit when fully exhausted can be regenerated by treating with 10% solution of sodium chloride. It is most efficient method to gel water with zero degree of hardness.

(vi) By synthetic resins

These are of two types:

(a) Cation exchange resins are big molecules containing sulphonic acid group (-SO3H). It is first changed into sodium salt with the general formula RNa. The hard water is passed through it so Ca2+ and M2+ are exchanged and removed.

The resins like permutit can be regenerated with a solution of NaCl.

(b) Anion exchange resins are also big molecules and can exchange anions. They contain an amino group.

The water is first passed through cation resins and then through anion tesin and pure distilled water is obtained.

Measurement of Degree of Hardness

Degree of hardness is defined as the number of parts of calcium carbonate or equivalent to various calcium and magnesium salts present in one million parts of water by mass. It is expressed in ppm.

Degree of hardness (in ppm) = (wt. of CaCO3 (g)/ wt. of hard water (g)) x 106

The molecular wt. of Ca(HCO3)2, Mg(HCO3)2, CaCl2, MgCl2, CaSO4 and MgSO4 is 162, 146, 111, 95, 136 and 120 respectively. The mol. wt. of CaCO3 is 100.

Thus, 162 g Ca(HCO3)2, 146 g Mg(HCO3)2, 111 gCaCl2, 95 g MgCl2 136 g CaSO4 and 120 g MgSO4 are equivalent to 100 g CaCO3.

Hydrogen Peroxide [H2O2]

H2O2 was discovered by J.L. Thenard in 1818. It is an important compound used in pollution control treatment of domestic and industrial effluents.

Methods of Preparation

Strength of Hydrogen Peroxide

The most common method to express the strength of H2O2 is in terms of the volume (in mL) of oxygen liberated at NTP by decomposition or 1 mL of that sample of H Z 0 2. A solution of H2O2 labelled as ’10 volume’ actually means “1 mL of such a solution of H2O2 on decomposition by heat produces 10 mL of oxygen at NTP”.

(i) Strength of H2O2 in terms of normality

(68 x X/22.4) = 17 x N ⇒ X = 5.6 x N

where, X is volume strength of H2O2.

(ii) % strength = (17/56) x volume strength

(iii) X = 11.2 x molarity.

Storage of Hydrogen Peroxide (H2O2)

It is stored in the presence of traces of alcohol, acetanilide or sodium pyrophosphate which slow down the rate of decomposition of hydrogen peroxide.

Chemical Properties of H2O2

Acidic nature It is weakly acidic in nature and pure hydrogen peroxide turns blue litmus red.

Oxidising agent It acts as a strong oxidising agent in acidic as well as in basic medium.

e.g., oxidising action of HzOz is

(iii) Reducing agent

(a) In acidic medium

(b) In basic medium

(iv) Bleaching properties Its bleaching action is due to oxidation by atomic oxygen and permanent.

H2O2 rarr; H2O + [O]

dye + [O] → dye is oxidised and bleached

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