Sulfuric acid

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(3) SO 3 (g) + H 2 O(l) → H 2 SO 4 (l)Note that directly dissolving SO 3 in water is not practical due to the highly exothermicnature of the reaction, forming a corrosive mist instead of a liquid. Alternatively, SO 3 canbe absorbed into H 2 SO 4 to produce oleum (H 2 S 2 O 7 ), which may then be mixed withwater to form sulfuric acid.(3) H 2 SO 4 (l) + SO 3 → H 2 S 2 O 7 (l)Oleum is reacted with water to form concentrated H 2 SO 4 .(4) H 2 S 2 O 7 (l) + H 2 O(l) → 2 H 2 SO 4 (l)[edit] Physical properties[edit] Forms of sulfuric acidAlthough nearly 100% sulfuric acid can be made, this loses SO 3 at the boiling point toproduce 98.3% acid. The 98% grade is more stable in storage, and is the usual form ofwhat is described as concentrated sulfuric acid. Other concentrations are used fordifferent purposes. Some common concentrations are10%, dilute sulfuric acid for laboratory use,33.53%, battery acid (used in lead-acid batteries),62.18%, chamber or fertilizer acid,73.61%, tower or Glover acid,97%, concentrated acid.Different purities are also available. Technical grade H 2 SO 4 is impure and often colored,but is suitable for making fertilizer. Pure grades such as United States Pharmacopoeia(USP) grade are used for making pharmaceuticals and dyestuffs.When high concentrations of SO 3(g) are added to sulfuric acid, H 2 S 2 O 7 , calledpyrosulfuric acid, fuming sulfuric acid or oleum or, less commonly, Nordhausen acid, isformed. Concentrations of oleum are either expressed in terms of% SO 3 (called% oleum)or as% H 2 SO 4 (the amount made if H 2 O were added); common concentrations are 40%oleum (109% H 2 SO 4 ) and 65% oleum (114.6% H 2 SO 4 ). Pure H 2 S 2 O 7 is a solid withmelting point 36°C.[edit] Polarity and conductivityAnhydrous H 2 SO 4 is a very polar liquid, having a dielectric constant of around 100. It hasa high electrical conductivity, caused by dissociation through protonating itself, a processknown as autoprotolysis. [3]
2 H 2 SO 4 ⇌ H 3 SO 4 + + HSO 4−The equilibrium constant for the autoprotolysis is [3]K ap (25°C)= [H 3 SO 4 + ][HSO 4 − ] = 2.7 × 10 −4 .The comparable equilibrium constant for water, K w is 10 −14 , a factor of 10 10 (10 billion)smaller.In spite of the viscosity of the acid, the effective conductivities of the H 3 SO 4 + and HSO 4−ions are high due to an intra-molecular proton-switch mechanism (analogous to theGrotthuss mechanism in water), making sulfuric acid a good conductor. It is also anexcellent solvent for many reactions.The equilibrium is actually more complex than shown above; 100% H 2 SO 4 contains thefollowing species at equilibrium (figures shown as millimol per kg solvent): HSO 4−(15.0), H 3 SO 4 + (11.3), H 3 O + (8.0), HS 2 O 7 − (4.4), H 2 S 2 O 7 (3.6), H 2 O (0.1). [3][edit] Chemical properties[edit] Reaction with waterThe hydration reaction of sulfuric acid is highly exothermic. If water is added to theconcentrated sulfuric acid, it can boil and spit dangerously. One should always add theacid to the water rather than the water to the acid. The necessity for this safety precautionis due to the relative densities of these two liquids. Water is less dense than sulfuric acid,meaning water will tend to float on top of this acid. The reaction is best thought of asforming hydronium ions, byand thenH 2 SO 4 + H 2 O → H 3 O + + HSO 4 − ,HSO 4 − + H 2 O → H 3 O + + SO 4 2− .Because the hydration of sulfuric acid is thermodynamically favorable, sulfuric acid is anexcellent dehydrating agent, and is used to prepare many dried fruits. The affinity ofsulfuric acid for water is sufficiently strong that it will remove hydrogen and oxygenatoms from other compounds; for example, mixing starch (C 6 H 12 O 6 ) n and concentratedsulfuric acid will give elemental carbon and water which is absorbed by the sulfuric acid(which becomes slightly diluted): (C 6 H 12 O 6 ) n → 6C + 6H 2 O. The effect of this can beseen when concentrated sulfuric acid is spilled on paper; the cellulose reacts to give aburned appearance, the carbon appears much as soot would in a fire. A more dramaticreaction occurs when sulfuric acid is added to a tablespoon of white sugar; a rigid columnof black, porous carbon will quickly emerge. The carbon will smell strongly of caramel.
Page 3 and 4: Related strongacidsRelatedcompounds
Page 5: Dissolved solids (TDS) concentratio
Page 9 and 10: Sulfuric acid production in 2000Sul
Page 13: Although sulfuric acid is non-flamm
Page 17 and 18: Pre-BoilingPour the dilute acid to
Page 19: maximum concentration of 98.3% H 2

Sulfuric acid

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