What is formula of oleum?

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Oleum (also known as fuming sulfuric acid) is a solution of sulfur trioxide (SO₃) dissolved in concentrated sulfuric acid (H₂SO₄). It is one of the most important industrial chemicals and a crucial intermediate in sulfuric acid production.1. Basic Oleum FormulasFormula TypeFormulaNameExplanationChemical FormulaH₂SO₄ · nSO₃Oleum (General)Where 'n' represents the number of SO₃ molecules per H₂SO₄ moleculeMolecular FormulaH₂S₂O₇Disulfuric AcidMost common form when n=1Structural FormulaHO-SO₂-O-SO₂-OHDisulfuric AcidShows the bonding arrangementAlternative RepresentationH₂SO₄ + SO₃Oleum SolutionShows composition as mixture2. Common Oleum ConcentrationsOleum TypeFormulaSO₃ ContentDescription20% OleumH₂SO₄ · 0.25SO₃20% free SO₃Light fuming sulfuric acid40% OleumH₂SO₄ · 0.67SO₃40% free SO₃Medium concentration oleum65% OleumH₂SO₄ · 1.84SO₃65% free SO₃High concentration oleum100% OleumSO₃100% SO₃Pure sulfur trioxide3. Formation and Preparation FormulasReaction TypeChemical EquationDescriptionDirect DissolutionH₂SO₄ + SO₃ → H₂S₂O₇SO₃ dissolves in concentrated H₂SO₄Contact Process2SO₂ + O₂ → 2SO₃ (then SO₃ + H₂SO₄)Industrial production methodPyrosulfuric Acid Formation2H₂SO₄ → H₂S₂O₇ + H₂ODehydration of sulfuric acid4. Molecular Structure and BondingAspectFormula/DescriptionDetailsMolecular WeightH₂S₂O₇ = 178.14 g/molFor disulfuric acidBond AnglesS-O-S ≈ 123°Angular structureHybridizationsp³ (Sulfur atoms)Tetrahedral around sulfurLewis Structure[Complex structure with double bonds]Contains S=O and S-OH bonds5. Chemical Properties FormulasHydrolysis ReactionsReactionEquationTypeWith WaterH₂S₂O₇ + H₂O → 2H₂SO₄Highly exothermicStepwise HydrolysisSO₃ + H₂O → H₂SO₄Liberation of SO₃ firstAcid-Base PropertiesPropertyFormula/ValueSignificancepH< 0 (extremely acidic)Stronger than concentrated H₂SO₄DissociationH₂S₂O₇ ⇌ H₂SO₄ + SO₃Releases free SO₃6. Physical Properties FormulasPropertyFormula/ValueUnitsDensityρ = 1.9-2.0g/cm³Boiling Point317°C (for H₂S₂O₇)°CMelting Point35°C (for H₂S₂O₇)°CVapor PressureHigh (fumes readily)mmHg7. Concentration CalculationsFormula for Oleum Strength% Free SO₃ = (Mass of free SO₃ / Total mass of oleum) × 100Converting Between Different ExpressionsFromToFormula% SO₃H₂SO₄ equivalent% H₂SO₄ = 100 + (0.225 × % SO₃)Molarity% SO₃Use density and molecular weights8. Industrial Applications FormulasApplicationRelevant FormulaProcessSulfonationR-H + SO₃ → R-SO₃HOrganic compound sulfonationDehydrationR-OH → R + H₂O (with oleum)Removal of water from alcoholsNitrationMixed acid preparationHNO₃ + H₂SO₄ system9. Safety and Handling FormulasHazard TypeRelated ChemistrySafety NoteHeat of DilutionΔH < 0 (highly exothermic)Always add oleum to water, never reverseCorrosivityDehydration reactionsDestroys organic matterFumingSO₃ vapor pressureHandle in well-ventilated areas

Reaction	Equation	Type
With Water	H₂S₂O₇ + H₂O → 2H₂SO₄	Highly exothermic
Stepwise Hydrolysis	SO₃ + H₂O → H₂SO₄	Liberation of SO₃ first

From	To	Formula
% SO₃	H₂SO₄ equivalent	% H₂SO₄ = 100 + (0.225 × % SO₃)
Molarity	% SO₃	Use density and molecular weights

What is formula of oleum?

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Formula Type	Formula	Name	Explanation
Chemical Formula	H₂SO₄ · nSO₃	Oleum (General)	Where 'n' represents the number of SO₃ molecules per H₂SO₄ molecule
Molecular Formula	H₂S₂O₇	Disulfuric Acid	Most common form when n=1
Structural Formula	HO-SO₂-O-SO₂-OH	Disulfuric Acid	Shows the bonding arrangement
Alternative Representation	H₂SO₄ + SO₃	Oleum Solution	Shows composition as mixture

Oleum Type	Formula	SO₃ Content	Description
20% Oleum	H₂SO₄ · 0.25SO₃	20% free SO₃	Light fuming sulfuric acid
40% Oleum	H₂SO₄ · 0.67SO₃	40% free SO₃	Medium concentration oleum
65% Oleum	H₂SO₄ · 1.84SO₃	65% free SO₃	High concentration oleum
100% Oleum	SO₃	100% SO₃	Pure sulfur trioxide

Reaction Type	Chemical Equation	Description
Direct Dissolution	H₂SO₄ + SO₃ → H₂S₂O₇	SO₃ dissolves in concentrated H₂SO₄
Contact Process	2SO₂ + O₂ → 2SO₃ (then SO₃ + H₂SO₄)	Industrial production method
Pyrosulfuric Acid Formation	2H₂SO₄ → H₂S₂O₇ + H₂O	Dehydration of sulfuric acid

Aspect	Formula/Description	Details
Molecular Weight	H₂S₂O₇ = 178.14 g/mol	For disulfuric acid
Bond Angles	S-O-S ≈ 123°	Angular structure
Hybridization	sp³ (Sulfur atoms)	Tetrahedral around sulfur
Lewis Structure	[Complex structure with double bonds]	Contains S=O and S-OH bonds

Property	Formula/Value	Significance
pH	< 0 (extremely acidic)	Stronger than concentrated H₂SO₄
Dissociation	H₂S₂O₇ ⇌ H₂SO₄ + SO₃	Releases free SO₃

Property	Formula/Value	Units
Density	ρ = 1.9-2.0	g/cm³
Boiling Point	317°C (for H₂S₂O₇)	°C
Melting Point	35°C (for H₂S₂O₇)	°C
Vapor Pressure	High (fumes readily)	mmHg

Application	Relevant Formula	Process
Sulfonation	R-H + SO₃ → R-SO₃H	Organic compound sulfonation
Dehydration	R-OH → R + H₂O (with oleum)	Removal of water from alcohols
Nitration	Mixed acid preparation	HNO₃ + H₂SO₄ system

Hazard Type	Related Chemistry	Safety Note
Heat of Dilution	ΔH < 0 (highly exothermic)	Always add oleum to water, never reverse
Corrosivity	Dehydration reactions	Destroys organic matter
Fuming	SO₃ vapor pressure	Handle in well-ventilated areas