By:- Atit s gaonkar XI A

INDEX Hydrogen

• Introduction.• Resemblance with alkali

metals. • Resemblance with halogen.• Difference from alkali metals

& halogen.• Isotopes.• Preparation of hydrogen.

• Properties of Dihydrogen.• Reactions• Uses of dihydroen.• Hydride.

Water.• Introduction.• Hard water soft water.• Removal of hardness.

HYDROGEN

•Hydrogen : It is the first element in the periodic table with the atomic number 1. The Hydrogen Ion ( H+ ) never exist in free state, it is always found in combined form.

•It resembles the first group elements and halogen group due to its anomalous character .

Introduction.

Electronic Configuration : contains one Electron In the outermost shell.

Electropositive : Like Alkali metals, Hydrogen also looses its one electron to form hydrogen ion, i.e., H+ .

Resemblance With Alkali Metals

Combination With Electronegative Elements : Like Alkali metals Hydrogen also combines with electronegative elements such as oxygen, sulphur, halogen.

Oxidation State : Like Alkali metals Hydrogen also shows the oxidation state of +1 I its compound.

Reducing Character : Like Alkali metals Hydrogen also act as a strong reducing agent.

Electronic Configuration : All the Halogen wants one electron to complete its octet, this property is shown by Hydrogen also.

Electronegative Character : Halogens have a strong tendency to gain electron to form halide, Hydrogen also shows same tendency.

Resemblance With Halogen

Ionization Enthalpy : Ionization Enthalpy of Hydrogen is quite comparable with those of the Halogen.

Oxidation State : Just Like halogen Hydrogen shows the oxidation state of -1.

Combination With Metals : Hydrogen combines with the metals in the same way as the halogens combine.

• Nature Of oxides : Hydrogen forms oxides that are neutral unlike alkali metals & halogen.

• Size Of ions : The Size Of ions Are Not Comparable with the size of the ions of alkali metals & halogen.

Difference From Alkali Metals & Halogens

Isotopes

• 1 H → Protium : The only isotope without neutron.

• 2 H → Deutrium : The isotope that is used as nuclear moderator in nuclear reaction .

• 3 H → Tritium : The only isotope of Hydrogen that is radioactive .

Lab Preparation : • Reaction Of dilute acid or bases

with granulated zinc

• Zn + HCl ZnCl2 + H2

• Zn + 2NaOH Na2ZnO2 + H2

Preparation Of Hydrogen

• Reaction with Water on Sodium Hydroxide.

• By reaction of KOH on scrap Aluminium. ( Uyeno’s Method )

Commercial Preparation • Electrolysis Of Acidified water

using platinum electrodes. Electrolysis 2 H2O (l) 2 H2

(g) + O2

• Brine solution : 2Na+ (aq) + 2Cl - + 2 H2O(l)

2NaCl + 2 H2O

• Reaction Of steam with Hydrocarbons in the presence of Catalysts.

CH4 + H2O CO + H2

• (Co + H2 ) → Water Gas or Syngas or Synthetic Gas• (CO + N2) → Producer Gas

• Coal Gasification Reaction• C(s) + H2O (g) CO + H2

• Water Gas Shift Reaction :• CO + H2O C O2 +

H2

• General Form:• Cn H2n+2 + n H2O nCO +

(2n+1) H2

Physical:

• Colourless, Tasteless & odourless.

• Lightest substance.

• Slightly soluble in water.

• Can be liquefied under low temperature & high pressure.

Properties Of Dihydrogen

Chemical:• Neutral Character.

• Reaction With Metal: 2Na + H2 2NaH

• Reaction With Dioxygen:

2 H2 + O2 2 H2O

Reactions

• Reaction With Halogen : H2 + X2 2HX (X=F,

Cl, Br, I)

• Reaction With Dinitrogen : N2 + 3H2 2NH3

• Reaction With Sulphur : H2 + S H2S

• Reaction With Carbon : C + 2H2 CH4

• Reduction Of Metal Oxides & Ions :• General form : MxOy + yH2 x M + yH2O

• Hydrogenation Of Unsaturated Hydrocarbons :

Unsaturated hydrocarbons such as alkenes & alkynes add Dihydrogen in presence of catalysts to form saturated hydrocarbons.

Hydroformulation : RCH=CH2 + H2 + CO RCH2CH2CHO

RCH2CH2CHO + H2 RCH2CH2C H2OH

• Hydrogenation of Vegetable Oil to solid fats.

• Manufacturing of bulk chemicals such as methanol.

• Manufacture of Ammonia ( Haber’s process ) .

Used Of Dihydrogen

• Manufacture Of metal Hydrides .

• In Metallurgy to reduce heavy metals.

• Used as liquid hydrogen.

• The various elements that form hydrides are

i. All the main group elements except those of noble gases & probably indium & Thallium.

ii. All Lanthanides & Actinides.iii. Transition elements . •On the basis of physical 7 chemical properties hydrides are categorized in three groups.

Hydrides

Ionic or salt like or Saline Hydrides :

• These are formed by transfer of electrons from the metals to the hydrogen atoms & thus contain hydride ion.

• The density of these hydrides is higher than those of the metals from which they are formed. This is because Hydrogen ion occupies holes in the lattice of the metal without disturbing the metal lattice.

• These are white crystalline solids 7 their crystal structure consists of ions.

• They have high melting & boiling points and conduct electricity in fused state, liberating Dihydrogen .

• They react violently with the water to form their respective metal hydroxides, with the liberation of Dihydrogen. The act as strong bases.

• They are very powerful reducing agents, especially at high temperature.

• They have high heat of formations 7 are always stoichiometric.

• Examples are NaH, CaH2 etc.

Metallic or Interstitial Hydrides :

• These are formed by the transition elements.

• They are hard, have a metallic luster, conduct electricity and have magnetic properties.

• The densities of these hydrides is lower than those metals of which they are formed since the crystal lattice expands due to inclusion of H2.

• The metals of group 7,8 and 9 do not form hydrides. Infact this region from group 7—9 is called as hydride gap.

• These hydrides are often non-stoichiometric .

• Example : La H2.87 , Ti H1.5-1.8 .

Molecular or Covalent Hydrides .

• When transition elements from hydride, they are called metallic or non-stoichiometric.

• On the basis of electron number the metallic hydride is classified is divided in three group.

i. Electron Deficient : BH3 13th group.

ii. Electron Precise : CH4 14th group.

iii. Electron Rich : H2O, NH3 15th, 16th, 17th

group.

water

Physical Properties :

• The freezing point , BP, heat of fusion, heat of vaporization, of water are very high because of the presence of intermolecular hydrogen bonding.

• Water has high specific heat, thermal conductivity, surface tension, high dielectric constant.

Introduction.

• Chemical properties :

• Amphoteric nature : H2O + N H3 O H- +

N + H4

(Acid) (Base) CB CA

H2O + H2S H3O+ + HS –

(Base) (Acid) CA CB

• Autoprotolysis : One molecule act as a base and another molecule acts as acid.

• Redox reactions involving H2O

H2O + Na NaOH + H2 .

( Reduction of H2O )

CO2 + H2O C6H12O6 + H2O + O2 .

( Reduction of H2O )

• Hardness of water depends upon hydrogen carbonate, chlorine, sulphate and salts of Ca & Mg.

• Temporary hardness is due to HCO3 Of Ca & Mg.

• Permanent Hardness is due to Cl and SO4 of Ca & Mg.

Hard Water & Soft Water

Removal Of Hardness

• Removal of temporary hardness: Boiling : Mg(HCO3) 2 Mg(OH)

2 + CO2

Ca(HCO3) 2 CaCO3 +

H2O + CO2

Removal Of Hardness

Clark’s Method : Uses Lime Water.

Ca(HCO3) 2 + Ca(OH) 2

CaCO3 + H2O

Mg(HCO3) 2 + Ca(OH) 2 Mg(OH) 2 + CaCO3 + H2O

• Removal of Permanent hardness :• This Can Be Removed By Using

Sodium Carbonate.

• MCl2 + Na2CO3 MCO3 + 2NaCl

• MSO4 + Na2CO3 MCO3 + 2Na2SO4

• By Using Calgon (Na2P6O18)

• Na2P6O18 (Na4P6O18)-2 + 2Na 2+

• Na4P6O18-2 (Na2MP6O18 ) -

2 + 2Na 2+

THANK YOU

That’s All From My Presentation

ATIT S. GAONKAR

BY:-

XI AKENDRIYA

VIDYALAYA KARWAR