22Hydrogen and its compounds

📚
HYDROGEN
▢ Basic Facts:
  • •
    Discoverer → Henry Cavendish
  • •
    Old name → inflammable air
  • •
    1st element in periodic table
  • •
    Atomic mass → 1.008 amu
  • •
    Electronegativity → 2.1
  • •
    Name coined by Lavoisier → hydrogen = water former
  • •
    Occurrence → free state + combined state
  • •
    Earth crust → nearly 1% by weight
  • •
    Position in periodic table → debatable
  • •
    Also called → rogue element
▢ Position in Periodic Table:
  • •
    Resembles alkali metals
  • •
    Resembles halogens
  • •
    Usually placed at top left of periodic table above group IA
  • •
    Kept separated from alkali metals due to distinctive characters
▢ Resemblance with Alkali Metals:
  • •
    Electronic configuration → 1s¹
  • •
    One outermost electron like alkali metals → ns¹
  • •
    Cation formation → H(1s¹) → H⁺ + e⁻
  • •
    H⁺ = smallest cation
  • •
    Combines with halogens → halides
  • •
    Combines with oxygen → oxides
  • •
    Combines with sulphur → sulphides
  • •
    Displaced from acids by metals → electropositive character
  • •
    Acts as reducing agent like alkali metals
▢ Reducing Examples:
  1. CuO + H₂ → Cu + H₂O
  2. B₂O₃ + 6K → 2B + 3K₂O
▢ Resemblance with Halogens:
  • •
    Diatomic gas like F₂ and Cl₂
  • •
    One electron short of stable configuration
  • •
    Forms hydrides with alkali and alkaline earth metals, similar to halides
  • •
    Ionization enthalpy closer to halogens than alkali metals
▢ Hydride and Halide Analogy:
  1. H₂ + 2Na → 2NaH
  2. Cl₂ + 2Na → 2NaCl
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PREPARATION OF HYDROGEN
▢ By Action of Water on Active Metals:
❖ Principle: Metals above hydrogen in electrochemical series liberate H₂ from water/acids.
❖ Reactions:
  1. 2Na + 2H₂O → 2NaOH + H₂↑
  2. Zn + H₂SO₄ → ZnSO₄ + H₂↑
❖ Notes:
  • •
    Higher position above H in electrochemical series → more vigorous reaction
  • •
    Zn + dilute H₂SO₄ = laboratory method
  • •
    Pure Zn not used because reaction is slow
  • •
    Concentrated H₂SO₄ not used because SO₂ is evolved instead of H₂
  • •
    Metals like Mg and Mn give small amount of H₂ with very dilute HNO₃
  • •
    H₂ bubbles may stick to Zn surface and stop further reaction
  • •
    Small amount of CuSO₄ prevents this by activating Zn surface
▢ By Action of Alkali on Amphoteric Metals:
❖ Metals: Zn, Al, Pb, Sn, As, Sb
❖ Reactions:
  1. Zn + 2NaOH → Na₂ZnO₂ + H₂↑
  2. 2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂↑
❖ Products:
  1. Na₂ZnO₂ → sodium zincate
  2. NaAlO₂ → sodium aluminate
❖ Special: Al + NaOH method = Uyeno's process
▢ By Action of Water on Metal Hydrides:
  1. LiH + H₂O → LiOH + H₂↑
  2. CaH₂ + 2H₂O → Ca(OH)₂ + 2H₂↑
▢ Hydrolith:
  • •
    CaH₂ = hydrolith
  • •
    Formation: Ca + H₂ → CaH₂
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INDUSTRIAL PREPARATION OF HYDROGEN
▢ Electrolysis of Water:
  • •
    Water contains small amount of acid/alkali: 15–20%
  • •
    H₂ liberated at cathode, usually iron cathode
  • •
    O₂ liberated at anode, usually nickel-plated iron rod
  • •
    Anode and cathode separated by asbestos diaphragm
  • •
    Asbestos diaphragm prevents mixing of H₂ and O₂
  • •
    Very pure H₂ obtained by electrolysis of Ba(OH)₂ solution because it is carbonate-free
▢ Water Gas / Bosch Process:
❖ Step 1: Water Gas Formation: C + H₂O → CO + H₂
❖ Condition: Red hot coke + steam, 440–600°C
❖ Step 2: Water Gas Shift: CO + H₂ + H₂O → CO₂ + 2H₂
❖ Catalyst: Fe₂O₃
❖ Promoter: Cr₂O₃
❖ Temperature: 440–550°C
❖ Purification: CO₂ removed by washing gaseous mixture with water under pressure
❖ Nature: Redox process
▢ Lane's Process: 3Fe + 4H₂O → Fe₃O₄ + 4H₂
▢ From Natural Gas:
❖ Reaction: CH₄ + H₂O → CO + 3H₂
❖ Catalyst: Ni or Cr
❖ Temperature: 900°C
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PHYSICAL PROPERTIES OF HYDROGEN
▢ General:
  • •
    Tasteless gas
  • •
    Odourless gas
  • •
    Colourless gas
  • •
    Lightest element
  • •
    Lightest gas
▢ Occlusion:
❖ Meaning: Adsorption/absorption of H₂ by metals.
❖ Metals: Fe, Au, Pt, Pd, Ni
❖ Occluded Hydrogen:
  • •
    Hydrogen adsorbed by metals
  • •
    Purest form of hydrogen
  • •
    Used for purification of hydrogen
  • •
    Released when metal is heated in vacuum
❖ Order: Colloidal Pd > crystalline Pd > Pt > Au > Ni > Fe
❖ Special: Powdered Pd can occlude nearly 1000 times its own volume of H₂.
📚
CHEMICAL PROPERTIES OF HYDROGEN
▢ Combustion:
  • •
    Combustible gas
  • •
    Burns in air/O₂ with nearly invisible pale blue flame
▢ Reducing Property:
  • •
    Reduces heated metallic oxides to metals
  • •
    Elements above hydrogen in electrochemical series are not reduced by H₂
  • •
    Examples not reduced by H₂ → Zn, Al, alkali metal oxides, alkaline earth metal oxides
▢ Reduction Reaction: CuO + H₂ → Cu + H₂O
▢ Hydrogenation:
  • •
    Converts unsaturated compounds to saturated compounds
  • •
    Catalyst → Ni
▢ Hydrogenation Reactions:
  1. CH₂=CH₂ + H₂ → CH₃–CH₃
  2. Vegetable oil + H₂ → vegetable ghee / vanaspati ghee
▢ Hardening of Vegetable Oil:
❖ Catalyst: Finely divided Ni
❖ Condition: High pressure, about 400°C
❖ Product: Solid fat / vanaspati ghee
▢ Uses in Flame:
  • •
    Liquid H₂ → cryogenic fluid
  • •
    Oxy-hydrogen flame → cutting and welding steel
  • •
    Atomic hydrogen flame → cutting and welding hard metals
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DIFFERENT FORMS OF HYDROGEN
▢ Atomic Hydrogen:
  • •
    Obtained by passing ordinary hydrogen through electric arc at about 2000°C
  • •
    Formation is endothermic
  • •
    Absorbed heat is stored in atoms
  • •
    Also prepared by irradiating hydrogen with mercury radiation
  • •
    Highly unstable
  • •
    Half-life about 0.3 second
  • •
    Atoms combine readily to form H₂ with large heat liberation
  • •
    Does not combine with nitrogen
  • •
    Can be isolated
  • •
    Cannot be prepared at room temperature
  • •
    Strongest reducing form of hydrogen
▢ Atomic Hydrogen Reductions:
  1. BaSO₄ + 8H → BaS + 4H₂O
  2. CO₂ + 2H → HCOOH
  3. CO + 2H → HCHO
  4. P₂O₅ → PH₃
▢ Nascent Hydrogen:
  • •
    Freshly produced hydrogen in contact with substance to be reduced
  • •
    Also called newborn hydrogen
  • •
    Cannot be isolated
  • •
    More active than ordinary molecular hydrogen
  • •
    Generated in situ
▢ Nascent Hydrogen Examples:
  1. Zn + H₂SO₄ → ZnSO₄ + 2H
  2. Fe³⁺ + H → Fe²⁺ + H⁺
  3. Acidified KMnO₄: purple → colourless
▢ Nascent Hydrogen Note:
  • •
    Ordinary H₂ does not reduce acidified KMnO₄ or FeCl₃ directly
  • •
    Nascent H produced in the same solution reduces them
  • •
    Nascent H cannot be isolated, but atomic H can be isolated
▢ Active Hydrogen:
  • •
    Obtained by silent electric discharge through molecular hydrogen
  • •
    Temperature: 60–80°C
  • •
    Exists at periphery of sun
  • •
    Used in hydrogen welding
  • •
    Hydrogen torch used in hydrogen welding
▢ Reducing Power Order: Ordinary H₂ < Nascent H < Active H < Atomic H
▢ Ortho and Para Hydrogen:
❖ Nature: Nuclear spin isomers of hydrogen.
❖ Ortho Hydrogen:
  • •
    Spins of two protons in same direction
  • •
    More stable than para form
  • •
    Ordinary hydrogen at 25°C contains 75% ortho form
❖ Para Hydrogen:
  • •
    Spins of two protons in opposite directions
  • •
    Lower energy form
  • •
    Favoured at low temperature
  • •
    At absolute zero, only para form exists
❖ Important Ratios:
  1. At 25°C equilibrium mixture → ortho : para = 3 : 1
  2. At 35 K → ortho : para = 1 : 1
  3. Lower temperature → para percentage increases
  4. Above 800°C → ortho percentage increases
❖ Other Points:
  1. Para hydrogen tends to revert into ortho hydrogen
  2. Thermal conductivity: para-H₂ > ortho-H₂
  3. Atomic H converts para-H₂ into ortho-H₂
📚
ISOTOPES OF HYDROGEN

Table 1: Isotopes of hydrogen

Isotope
Symbol
Proton
Electron
Neutron
Remarks
Protium
¹H₁ / H
1
1
0
Most abundant
Deuterium
²H₁ / D
1
1
1
Heavy hydrogen; forms heavy water
Tritium
³H₁ / T
1
1
2
Radioactive
▢ Important Points:
  • •
    Protium forms simple water
  • •
    Deuterium forms heavy water
  • •
    Tritium is radioactive
  • •
    Ordinary hydrogen: protium : deuterium = 6400 : 1
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USES OF HYDROGEN
▢ Liquid Hydrogen:
  • •
    Rocket fuel
  • •
    High calorific value
  • •
    High heating ratio
  • •
    Small mass
  • •
    Large quantity of heat production
  • •
    Cryogenic fluid to maintain low temperature
▢ Hydrogen Economy:
❖ Meaning: Use of liquid hydrogen as alternate energy source.
❖ Advantages:
  • •
    More energy per unit weight of fuel
  • •
    No pollution by CO, SO₂, hydrocarbons, lead etc.
  • •
    High efficiency: 70–85%
  • •
    Fuel cells convert H₂–O₂ chemical energy into electrical energy
📚
HYDRIDES
▢ Definition: Compounds formed by combination of hydrogen with metals or non-metals.
▢ Types:
  1. Ionic / salt-like / saline hydrides
  2. Molecular / covalent hydrides
  3. Metallic / interstitial hydrides
  4. Polymeric hydrides
  5. Complex hydrides
▢ Ionic / Salt-like / Saline Hydrides:
  • •
    Hydrogen oxidation state → −1
  • •
    Formed by highly electropositive metals
  • •
    Formed mainly by alkali and alkaline earth metals except Be and Mg
  • •
    Example: CaH₂ / hydrolith
  • •
    Crystalline solids
  • •
    Conduct electricity in fused state
  • •
    Used as solid fuel
▢ Thermal Stability of Ionic Hydrides:
  1. LiH > NaH > KH > RbH > CsH
  2. CaH₂ > SrH₂ > BaH₂
▢ Molecular / Covalent Hydrides:
  • •
    Hydrogen oxidation state → +1
  • •
    Formed by highly electronegative elements / non-metals
  • •
    Mostly covalent
  • •
    Molecules held by weak van der Waals forces
▢ Stability of Covalent Hydrides:
  1. Down group: NH₃ > PH₃ > AsH₃ > SbH₃ > BiH₃
  2. Across period: CH₄ < NH₃ < H₂O < HF
▢ Metallic / Interstitial Hydrides:
  • •
    Non-stoichiometric hydrides
  • •
    Formed by d-block and f-block elements
  • •
    Hydrogen atoms occupy interstitial sites in metal lattice
  • •
    Strong reducing agents
  • •
    Suggest hydrogen in atomic state
  • •
    Example: ThH
▢ Polymeric Hydrides:
  • •
    Formed by group 13 / boron family
  • •
    Examples: B₂H₆, (AlH₃)n
▢ Complex Hydrides:
  1. LiAlH₄
  2. LiBH₄
  3. NaBH₄
Nitrogen Hydrides
Hydrides of nitrogen are basic except hydrazoic acid HN₃.
Reducing Nature
Hydrogen and hydrides act as reducing agents.
📚
PURIFICATION AND DRYING OF HYDROGEN
▢ Laboratory Purification:

Table 1: Impurity removal

Reagent
Removes
AgNO₃ solution
PH₃, AsH₃
CuSO₄ solution
NH₃, H₂S
Caustic soda / NaOH
CO₂, SO₂, NO₂
▢ Drying:
  • •
    Moist H₂ dried by anhydrous CaCl₂
  • •
    Moist H₂ dried by P₂O₅
▢ N₂ Contamination: Dry H₂ contaminated with N₂ is passed over heated Pd; Pd absorbs H₂ only and N₂ passes away.
▢ Hydrazoic Acid:
  • •
    Hydrazoic acid + metal → azides
  • •
    Azides used as blood preservatives and anticoagulants
📚
WATER
▢ Composition:
  • •
    Gravimetric composition H : O = 1 : 8
  • •
    Volumetric composition H : O = 2 : 1
  • •
    Gravimetric composition established by Dumas
  • •
    Water contains 8 parts oxygen and 1 part hydrogen by weight
▢ Physical Data:

Table 1: Water constants

Property
Value
Dielectric constant
81
Maximum density
4°C
Density at 4°C
1 g/cc
State
Liquid due to hydrogen bonding
Dipole moment
1.85 Debye
▢ Structure:
  • •
    Central atom → oxygen
  • •
    Hybridisation of O → sp³
  • •
    Shape → bent / V-shaped
  • •
    Bond angle → 104.5°
  • •
    Normal tetrahedral angle → 109°28′
  • •
    Decrease in bond angle due to two lone pairs on oxygen
  • •
    Water molecule is polar
▢ Density Anomaly:
  • •
    Water has higher density than ice
  • •
    Ice floats on water
  • •
    Useful for aquatic life
  • •
    Due to intermolecular hydrogen bonding and packing difference
▢ High Melting and Boiling Point:
  • •
    Higher than hydrides of group VIA
  • •
    Reason → hydrogen bonding
▢ Solvent Property:
  • •
    Universal solvent
  • •
    Leveling solvent
  • •
    Polar inorganic solvent
  • •
    Ionic compounds generally soluble
  • •
    Solubility when hydration energy > lattice energy
  • •
    Covalent compounds generally insoluble due to absence of hydrogen bonding
▢ Exceptions:
❖ Insoluble Ionic Compounds:
  1. AgCl
  2. BaSO₄
  3. CaF₂
❖ Soluble Organic Compounds:
  1. Alcohols
  2. Carboxylic acids
  3. Carbohydrates
❖ Reason: Hydrogen bonding with water
▢ Sterilization of Water:
  • •
    Removal of harmful bacteria from drinking water
  • •
    Methods → chlorination, boiling, ozonisation, aeration, UV rays
📚
HEAVY WATER
▢ Basic Facts:
  • •
    Formula → D₂O
  • •
    Also called → deuterium oxide
  • •
    Discovered by Urey
  • •
    Dielectric constant → 80.5
  • •
    Temperature of maximum density → 11.6°C
  • •
    NaCl is less soluble in heavy water than ordinary water
  • •
    Ordinary water contains small fraction of heavy water
  • •
    About 60 × 10³ L ordinary water contains nearly 1 L D₂O
▢ Comparison with Ordinary Water:

Table 1: H₂O vs D₂O

Property
H₂O
D₂O
Freezing point
0°C
3.82°C
Boiling point
100°C
101.42°C
Density at 20°C
0.9982 g/cc
1.106 g/cc
Temperature of maximum density
4°C
11.6°C
Dielectric constant at 20°C
82
80.5
▢ Recovery from Ordinary Water:
  1. Fractional distillation
  2. Prolonged electrolysis of ordinary water containing alkali
▢ Applications:
  • •
    Moderator in nuclear reactor
  • •
    Slows down neutrons
  • •
    Used in medical science for isotopic study of cancer-affected tissue
📚
HARD AND SOFT WATER
▢ Hard Water:
  • •
    Contains soluble salts of Ca²⁺ and Mg²⁺
  • •
    Does not give lather with soap
  • •
    Examples → sea water, river water, spring water
▢ Soft Water:
  • •
    Pure water or water containing Na salts
  • •
    Gives lather easily with soap
  • •
    Examples → rain water, distilled water, demineralised water
▢ Hardness of Water:
❖ Cause: Soluble bicarbonates, chlorides and sulphates of calcium and magnesium.
❖ Distilled Water pH: pH < 7 due to atmospheric CO₂ forming H₂CO₃
▢ Types of Hardness:

Table 1: Temporary vs permanent hardness

Type
Cause
Heat effect
Temporary hardness
Bicarbonates of Ca and Mg
Decomposes on heating
Permanent hardness
Chlorides and sulphates of Ca and Mg
Stable to heat
▢ Degree of Hardness:
  • •
    Amount of hardness-causing substances in a given volume of water
  • •
    Calculated as calcium carbonate equivalent
  • •
    Expressed as ppm of CaCO₃
▢ Estimation: EDTA is used for estimation of hardness of water.
📚
REMOVAL OF HARDNESS
▢ Basic Principle: Precipitation or complex formation of Ca²⁺ and Mg²⁺ salts.
▢ Temporary Hardness Removal:
❖ Boiling:
  1. Ca(HCO₃)₂ → CaCO₃↓ + CO₂↑ + H₂O
❖ Clark's Method:
  1. Calculated quantity of slaked lime is added
  2. Ca(HCO₃)₂ + Ca(OH)₂ → 2CaCO₃↓ + 2H₂O
▢ Permanent Hardness Removal:
❖ Washing Soda Method:
  1. Washing soda removes both temporary and permanent hardness
  2. MgSO₄ + Na₂CO₃ → MgCO₃↓ + Na₂SO₄
❖ Soda-Lime Method: Removes both types of hardness.
❖ Calgon Process:
  • •
    Based on formation of soluble complex
  • •
    Calgon = sodium hexametaphosphate
  • •
    Formula → Na₂[Na₄(PO₃)₆]
  • •
    Ca²⁺ and Mg²⁺ form complex ions that do not precipitate with soap
❖ Calgon Reaction: Ca²⁺ + Na₂[Na₄(PO₃)₆] → 4Na⁺ + [Na₂Ca(PO₃)₆]²⁻
❖ Permutit Method:
  • •
    Permutit = artificial zeolite
  • •
    Also called sodium zeolite
  • •
    Trade name of sodium aluminium orthosilicate
  • •
    Formula → Na₂Al₂Si₂O₈·xH₂O
  • •
    Exchanges Na⁺ with Ca²⁺ and Mg²⁺
  • •
    10% NaCl brine regenerates exhausted permutit
❖ Permutit Reaction: Na₂Al₂Si₂O₈·xH₂O + MgCl₂ → MgAl₂Si₂O₈·xH₂O + 2NaCl
▢ High-Yield Notes:
  • •
    Calgon removes hardness by soluble complex formation, not precipitation
  • •
    Ion exchange resin method converts hard water into demineralised water
  • •
    Permanent hardness removal methods also remove temporary hardness
  • •
    Boiling and Clark's method remove only temporary hardness
  • •
    AgCl, CaF₂ and BaSO₄ are water-insoluble ionic compounds
  • •
    CaF₂ is also called John blue
  • •
    Potash alum is used as water purifier
▢ Test of Water:
  • •
    Anhydrous cobalt chloride: blue → pink on hydration
  • •
    Anhydrous CuSO₄: white → blue on hydration
📚
HYDROGEN PEROXIDE
▢ Basic Facts:
  • •
    Formula → H₂O₂
  • •
    Also called → oxygenated water
  • •
    Pale blue syrupy liquid
  • •
    Diamagnetic
  • •
    Prominent hydrogen bonding than water
  • •
    Pure solution → weakly acidic
  • •
    Aqueous solution → neutral
  • •
    Antiseptic and germicide
  • •
    Oxidising agent in laboratory
  • •
    Used for bleaching substances
▢ Structure:
  • •
    Non-planar molecule
  • •
    All atoms do not lie in same plane
  • •
    Open-book structure
▢ Preparation:
❖ From Hydrated Barium Peroxide:
  1. BaO₂·8H₂O + H₂SO₄ → BaSO₄↓ + H₂O₂ + 8H₂O
  2. H₃PO₄ is better than H₂SO₄ in laboratory preparation because it acts as negative catalyst for H₂O₂ decomposition
❖ Merck's Process:
  1. Na₂O₂ + H₂SO₄ → Na₂SO₄ + H₂O₂
  2. Calculated amount of sodium peroxide is added to 20% cold H₂SO₄
▢ Manufacture:
❖ Electrolysis of 50% H₂SO₄:
  1. After manufacture, acid concentration increases
  2. Cathode: 2H⁺ + 2e⁻ → 2H → H₂↑
  3. Anode: 2HSO₄⁻ → H₂S₂O₈ + 2e⁻
  4. H₂S₂O₈ = Marshall acid / peroxodisulphuric acid
  5. H₂S₂O₈ + 2H₂O → 2H₂SO₄ + H₂O₂
❖ Anthraquinol Process:
  1. 2-ethyl anthraquinol → 2-ethyl anthraquinone + H₂O₂
▢ Decomposition:
  • •
    Unstable on standing or heating
  • •
    2H₂O₂ → 2H₂O + O₂
  • •
    Auto-oxidation reaction
  • •
    Catalysed by Pt, Ag, Fe, Cu, MnO₂, Co
▢ Bleaching Action:
  • •
    Dry bleach
  • •
    Permanent bleaching
  • •
    Oxidation process
▢ Acidic Property:
  • •
    Can form peroxides
  • •
    Acts as acid with bases
▢ Peroxide Formation:
  1. Na₂CO₃ + H₂O₂ → Na₂O₂ + H₂O + CO₂
  2. Ba(OH)₂ + H₂O₂ → BaO₂ + 2H₂O
📚
OXIDISING AND REDUCING PROPERTIES OF H₂O₂
▢ Oxidising Property:
  • •
    Acts in acidic, alkaline and neutral medium
  • •
    Dissociates to give H⁺ and hydroperoxide ion HO₂⁻
▢ H₂O₂ Oxidises:
  1. PbS → PbSO₄
  2. FeSO₄ → ferric salt
  3. KI → I₂
  4. Sodium arsenite → sodium arsenate
  5. Potassium ferrocyanide → potassium ferricyanide
▢ Oxidising Power Order: F₂ > atomic O > OF₂ > O₃ > H₂O₂ > KMnO₄ > K₂Cr₂O₇
▢ Reducing Property:
  • •
    Acts in acidic, alkaline and neutral medium
  • •
    Reduces halogens to halogen acids
  • •
    Reduces potassium dichromate to chromium sulphate
  • •
    Reduces ozone to oxygen in neutral medium
▢ Lead Paint Restoration:
❖ Concept: Old lead paint blackened by H₂S is restored by H₂O₂.
❖ Reaction: PbS + 4H₂O₂ → PbSO₄ + 4H₂O
❖ Colour Change: Black PbS → white PbSO₄
▢ Antichlor:
  • •
    Substance that removes or dissolves Cl₂ left after bleaching
  • •
    Examples → H₂O₂, SO₂, Na₂S₂O₃ solution
▢ Perhydrol:
  • •
    30% aqueous H₂O₂ solution
  • •
    Used as antiseptic
  • •
    Used as mouth-washing liquid
  • •
    Molarity → 8.8
📚
STORAGE, TEST AND CONCENTRATION OF H₂O₂
▢ Storage:
  • •
    Stored in Teflon bottle or acid-proof plastic bottle
  • •
    Paraffin wax layer used
  • •
    Bottle surface should be smooth
  • •
    Negative catalysts/inhibitors added → H₃PO₄, glycerol, acetanilide
  • •
    Not stored in glass because alkaline oxides in glass catalyse decomposition
▢ Test:
  • •
    In presence of FeSO₄, H₂O₂ turns starch iodide paper blue
  • •
    In absence of FeSO₄, both H₂O₂ and O₃ turn starch iodide paper blue
▢ Volume Strength:
  • •
    Expressed as volume of O₂ at NTP obtained by decomposition of 1 mL H₂O₂ solution
  • •
    Volume strength = 5.6 × Normality
  • •
    10 volume H₂O₂: 1 mL solution gives 10 mL O₂ at NTP
  • •
    20 volume H₂O₂: 1 mL solution gives 20 mL O₂ at NTP
▢ Equivalent Weight: Equivalent weight of H₂O₂ = 17
▢ Important Relations:
  1. 10 volume H₂O₂ = 3.035% H₂O₂
  2. 10 volume H₂O₂ = 30.35 g/L H₂O₂
  3. 10 volume H₂O₂ = 1.75 N
  4. 10 volume H₂O₂ ≈ 1.79 N
  5. 30 volume H₂O₂ ≈ 5.35–5.37 N
▢ Numerical Facts:
  • •
    1 L of 2 M H₂O₂ contains 68 g H₂O₂
  • •
    100 mL of 2 M H₂O₂ contains 6.8 g H₂O₂
  • •
    Complete decomposition of 100 mL of 2 M H₂O₂ gives 2.24 L O₂ at STP
  • •
    30 volume H₂O₂ contains about 91.07 g/L H₂O₂
📚
HYDRATES AND WATER OF CRYSTALLIZATION
▢ Types of Hydrates:

Table 1: Hydrates

Type
Meaning
Example
Cationic hydrates
Water molecules held by cations
MgCl₂·6H₂O, CaCl₂·6H₂O
Lattice hydrates
Water molecules held in lattice sites
Na₂CO₃·10H₂O
Anionic hydrates
Water molecules held by anions and cations
CuSO₄·5H₂O, MgSO₄·7H₂O
▢ Absorption and Loss of Water:

Table 1: Water absorption/loss

Term
Meaning
Examples
Hygroscopic
Absorb moisture from air
NH₄NO₃
Deliquescent
Absorb large amount of water and dissolve
NaOH, CaCl₂, NaNO₃
Efflorescent
Lose water of crystallization
CaSO₄·2H₂O, CuSO₄·5H₂O, MgSO₄·7H₂O, FeSO₄·7H₂O
📚
SOAPS AND DETERGENTS
▢ Soaps:
  • •
    Sodium or potassium salts of higher fatty acids
  • •
    Sodium salts → hard soap / washing soap
  • •
    Potassium salts → soft soap / bath soap
  • •
    Process of soap formation → saponification
  • •
    Soaps of metals other than Na or K are usually insoluble in water
  • •
    Dirt is removed by action of water on soap
▢ Synthetic Detergents:
  • •
    Also called soapless soaps or syndets
  • •
    May or may not be biodegradable
  • •
    Common group → R–O–SO₃–Na
▢ Types of Synthetic Detergents:
  1. Sodium alkyl sulphates, e.g. sodium lauryl sulphate
  2. Sodium alkyl aryl sulphonates, e.g. sodium dodecyl benzene sulphonate
📚
READ AND DIGEST POINTS
▢ Hydrogen and Water:
  • •
    Two ice cubes pressed together form a single cube due to hydrogen bonding
  • •
    Ozone purifies water by destroying viruses and bacteria
  • •
    Sea water can be purified by reverse osmosis
  • •
    Non-metallic character of H₂O distinguishes it from alkali metals
  • •
    Hydrogen has negative valency in NaH
  • •
    Surface water contains salts and organic matter
  • •
    AgI is used for artificial rain
  • •
    0.9% NaCl solution is isotonic with human blood
  • •
    Zeolite is a silicate compound
  • •
    Sodium catches fire with water due to burning of H₂
▢ Hydrogen Peroxide:
  • •
    H₂O₂ is neutral, but commercial H₂O₂ is acidic
  • •
    Aqueous H₂O₂ is neutral
  • •
    H₂O₂ is better oxidising agent than reducing agent
  • •
    H₂O₂ shows auto-oxidation
  • •
    H₂O₂ oxidises MnSO₄ to MnO₂ in alkaline medium
  • •
    H₂O₂ oxidises KNO₂ to KNO₃ in neutral medium
  • •
    H₂O₂ reduces O₃ to O₂ in neutral medium
  • •
    H₂O₂ is not stored in glass because alkaline oxides in glass catalyse decomposition
  • •
    Decomposition of H₂O₂ is slowed by alcohol
  • •
    Reaction of H₂O₂ with H₂S is a redox reaction
  • •
    Decomposition of H₂O₂ is favoured by MnO₂
  • •
    2H₂O₂ → 2H₂O + O₂ shows decomposition of H₂O₂
  • •
    Industrial preparation of H₂O₂ is generally by electrolysis of 50% H₂SO₄
  • •
    H₂O₂ used as rocket fuel at about 90% concentration
  • •
    H₂O₂ is used for bleaching hair
▢ Addition Reaction of H₂O₂: CH₂=CH₂ + H₂O₂ → HO–CH₂–CH₂–OH
Q1.
Which of the following doesn't displace hydrogen?
📅IOM 2066
Q2.
A deuteron contains
📅MOE
Q3.
Ortho and para hydrogen differ in
📅I.E.
Q4.
Hydrogen, deuterium and tritium have
📅MOE
Q5.
In preparation of vanaspati ghee, the reaction involving hydrogen is called
📅IOE/MOE
Q6.
Hydrogen forms
📅IOE
Q7.
The most reactive form of hydrogen is
📅I.E.
Q8.
Ortho and para forms of hydrogen can be separated by
📅I.E.
Q9.
Lane's process is for
📅K.U.
Q10.
Atomic hydrogen produces formaldehyde when it reacts with
📅IOM 2004
Q11.
Hydrogen cannot be obtained by
📅IOM 2005
Q12.
Hydrogen burns in air with a
📅MOE
Q13.
Which particle is emitted by tritium?
📅I.E.
Q14.
Which has equal no. of neutrons and protons?
📅BPKIHS 2005
Q15.
H loses electron to form H⁺. In this aspect H behaves as
📅MOE 2008
Q16.
Finely divided nickel is used as a catalyst in
📅MOE 2050
Q17.
Which is reduced by H₂?
📅MOE 2069
Q18.
Hydrogen differs from halogens in
📅Bangladesh, Embassy 2001
Q19.
Which contains acidic hydrogen atom?
📅K.U. 2004
Q20.
NaI is an example of
📅I.E. 2001
Q21.
The gas used in sterilizing water is
📅MOE 2066
Q22.
Heavy water is used as
📅BPKIHS
Q23.
Maximum hydrogen bonds a water molecule can form is
📅BPKIHS
Q24.
Which produces hard water?
Q25.
Calgon's process uses
📅MOE
Q26.
Best method to test water presence?
📅MOE, IOM 1998
Q27.
High density of water vs ice is due to
📅MOE
Q28.
A hydrated salt losing water in air is called
📅MOE
Q29.
Calgon is
📅MOE/IOM 2004
Q30.
Water is
📅IOM 1994
Q31.
A dilute H₂O₂ solution can be concentrated by
Q32.
Fenton's reagent is
📅BPKIHS
Q33.
The oxide that gives H₂O₂ with dilute acid is
📅BPKIHS
Q34.
Moderator in nuclear reactor is
📅BPKIHS
Q35.
H₂S + H₂O₂ → S + H₂O shows
📅MOE
Q36.
Volume strength of 1.5 N H₂O₂ is
Q37.
H₂O₂ acts as oxidizing agent with
📅BPKIHS
Q38.
Permanent hardness is due to
📅BPKIHS
Q39.
Calgon process involves
📅MOE 2003
Q40.
Acid rain doesn't contain
📅MOE 2060
Q41.
Which is correct?
📅MOE 2050