Hydrogen

Similarity of Hydrogen to alkali metals

1. 1 valence electron

2. Forms compounds with oxygens and halogens

3. Forms monovalent cations

Similairty of hydrogen to halogens

1. Tendency to gain 1 electron

2. High ionisation energy

3. Forms compounds like halogens

4. Does not posses metallic character.

Which is the most abundant element

Hydrogen

Which are the three isotopes of hydrogen and what are their mass numbers

Protein (1) , Dueterium (2) , Tritium (3)

Which is the radioactive isotope of hydorgen , what does it emmit?

Tritium , it emits low energy beta rays

Prepararation of Dihydrogen (H₂) in laboratory

What are the common industrial methods of prepartion of dihydrogen

1. Electrolysis of acidified water using platinum electrodes

2. High purity dihydorgen is obtained by electrolysis warm aqueous Ba(OH)₂

3. Byproduct of chlor-alkali process

4. Lane’s Method from iron filings

5. Stream reforming process , reacting steam with hydrocarbons or coke.

How does dihydrogen react with dioxygen

2H₂ + O₂ → 2H₂O

Reaction of hydrogen and di nitrogen

3H₂ + N₂ → 2NH₃

What are the uses of Dihydrogen

1. Synthesis of ammonia

2. Hydrogen of polyunsaturated vegetable oils

3. Manufacturing organic chemicals like methanol

4. Producing HCL and other acids

5. Reducing metal oxides

6. Fuel source

Properties of Hydrogen

1. Colourless , Odourless , Tasteless

2. Highly combustible

3. Lighter than air

4. Insoluble in water

What are hydrides?

Dihydrogen under certain conditions react with all elements except noble gases to form binary compounds called hydrides.

How is hydrogen produced from warm Ba(OH)₂

Ba(OH)₂ → Ba∙² + OH⁻

H₂O →∆ H⁺ + OH⁻

Explain brine electrlysis

1. NaCl breaks to form chlorine gas at anode

2. Water breaks down to evolve hydrogen at cathode

Equation for Lane’s Method

Fe + H₂O →∆ Fe₂O₃ + H₂

If excess steam is given Fe₃O₄ is formed instead

What is ortho and para hyrdogen

They are spin isotopes , ortho has spin in same direction while para has spin in different directions.

Does para or ortho have hgiher internal energy

Ortho

What is spin isomer compostion at room temperature

75% ortho , 25% para

Which spin isomer is hundred percent at absolute 0

para

_____ hydrogen has 50% greater thermal conduction.

para

Para hydrogen melts at 15k _____ (higher/lower) than ortho hydrogen

lower

Is hydrogen lighter than air?

Yes

What is water gas

Mixture of CO and H₂

What is watergas also called as

syngas or synthetic gas

Enumerate on the bond dissociation enthalpy of hydrogen

H-H bond dissociation enthalpy is the highest for a single element.

Under what conditions is atomic hydrogen produced.

It is produced at high temperatures in an electric arc or under ultraviolet radiation.

How is hydorgen used to produce alcohol.

Hydroformylation of Olefins yields aldehydes which further undergo reduction to give alcohols.

What are the other names for Ionic Hydrides

Salt-like hydride , saline hydride

What are ionic hydrides?

They are made by the combination of dihydrogen formed with s-block elements (Na , Ca , Mg , Sr , Li , Be , K)

What are the properties of ionic hydrides

1. White crystaline solid

2. Ionic Lattice

3. High melting and boiling point

4. Non Volatile

5. Reacts violently with water producing hydrogen.

What happens when saline hydrides react with water?

Saline hydrides react violently with water producing dihydrogen gas.

NaH + H₂O → NaOH + H₂

Is litium hydride reactive with O₂ or Cl₂

8LiH + Al₂Cl₆ → 2LiAlH₄

What are covalent hydrides?

Dihydrogen reacts with p-block elements to form saline hydrides.

What are the properties of covalent hydrides?

1. Volatile Compounds

2. Low melting point

3. Low boiling point

What are the types covalent hydrides?

1. Electron deficient

2. Electron Precise

3. Electro Rich

What are electron deficient hydrides and its properties.

An electron deficient hydrides has fewer electrons for writing its conventional Lewis structure.

They are group 13 elements

They accept electrons and act as lewis acids.

What are electron precise hydrides and it’s properties?

• Electron precisie compounds have required number of electrons to write conventional Lewis structures.

• All elements from group14 form such compounds

• They are tetrahedral in geometry.

Electron rich hydrides it’s properties.

• Electron rich hydrides have excess electrons which are presenet as lone pairs.

• Elements of Group 15-17 form such hydrides.

• They are electron donors and behave as Lewis Base

• They are highly electrognegative due to presenece of lone pairs

Metallic Hydrides and its properties

• They are formed by d and f block elements except group 9 , 8 and 7

• They conduct heat and electricity and are non stoichipmetirc.

• The lattice of the hydrides different from parent metal and absorb hydrogen

• Hydrogen occupies interstetial spaces in Ni . Pd , Ce and Ac.

• Metallic hydrides are used for reduction / hydorgenation reaction.

What are the physical properties of Water.

1. Melting Pint - 273K

2. Boiling Point 373K

3. In solid state (ice) water exists as an open cage structure

4. High Di-electric constant (acts as a good solvent for ionic compounds)

5. High heat of vaporisation and heat capactiy are responsible for moderation.

6. Due to hydrogen bonding with polar molecules even covalent compounds like alcohol and carbohydrates dissolve in water.

What are chemical properties of water

1. Acts as an oxidant as well as reductant

2. When it acts as oxidant , it will oxidise and itself will get reduced

3. When it acts as reductant , it will reduce and itself get oxidised.

Forms of bonded water?

1. Hydrates - in the form of water of crystallisation , BaCl₂.2H₂O , CaSO₄.2H₂O

2. Coordinated Water - when it forms covalent bond [Cr(H₂O)₆]⁻³

3. H-bonded Water - [Cu(H₂O)₄]²⁺SO₄²⁻ in CuSO₄.5H₂O

What are the methods of preparation of Hydrogen Peroxide.

1. Acidifying barium peroxide and removing excess water by evaporation under reduced pressure

   1. BaO₂.8H₂O + H₂SO₄ → BaSO₄ + H₂O₂ + 8H₂O

2. Peroxodisulphate , obtained by electrolytic oxidation

   1. 2HSO₄⁻¹ → HO₃SOOSO₃ (Electrolysis)

   2. HO₃SOOSO₃ → 2HSO₄⁻ + 2H⁺ + H₂O₂ (Hydrolysis)

3. Auto-oxidation of 2-alkluanthraquinols