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Sulphur and its Compounds. Chapter 42. General properties. Group VIA (1s 2 2s 2 2p 6 3s 2 3p 4 ) m.p. 113 o C, b.p. 445 o C Allotropes: (1) Rhombic sulphur, S 8 (room to 96 o C) (2) Monoclinic sulphur, S 8 (stable btn. 96-119 o C) (3) Plastic sulphur, long polymeric chains.
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Sulphur and its Compounds Chapter 42
General properties • Group VIA (1s22s22p63s23p4) • m.p. 113oC, b.p. 445oC • Allotropes: • (1) Rhombic sulphur, S8 (room to 96oC) • (2) Monoclinic sulphur, S8 (stable btn. 96-119oC) • (3) Plastic sulphur, long polymeric chains.
Burning of sulphur • Sulphur burns with a dull blue flame to form sulphur dioxide, trace of misty sulphur trioxide are also formed. • S + O2 SO2
Sulphur dioxide • A colourless gas with choking smell • An acidic gaseous pollutant • Readily liquefied under pressure • Very soluble in water and reacts to form sulphuric(IV) acid • Can be further oxidized to SO3, which dissolves in water to form sulphuric(VI) acid, H2SO4
Oxidizing properties of SO2 • 2Mg + SO2 2MgO + S • 2H2S + SO2 2H2O + 3S • Aqueous SO2 SO32-(aq) • 2MnO4- + 5SO32- + 6H+ 2Mn2+ + 5SO42- + 3H2O • Cr2O72- + 3SO32- + 8H+ 2Cr3+ + 3SO42- + 4H2O
Oxidizing properties of SO2 • Br2+ SO32- + H2O 2Br- + SO42- + 2H+ • Dye + SO32- + H2O Dye-O + SO42- + 2H+
Sulphuric(VI) Acid • Contact Process • S + O2 SO2 (or 4FeS2 + 11O2 2Fe2O3 + 8SO2) • 2SO2 + O2 2SO3 (450oC, V2O5 as catalyst) • SO3 + H2SO4 H2S2O7 (then H2S2O7 + H2O 2H2SO4)
Catalytic chamber Heat exchanger Sulphur burner Air drySO2+air Purifier and drier Purifier and drier water Air SO3 Absorption tower H2SO4 store oleum 98% H2SO4 c.H2SO4 A flow diagram
Chemical properties of H2SO4 • Dilute H2SO4, a typical acid • Zn + H2SO4 ZnSO4 + H2 • 2NaOH + H2SO4 Na2SO4 + H2O • CuO + H2SO4 CuSO4 + H2O • MgCO3 + H2SO4 MgSO4 + H2O + CO2 • 2NaHCO3 + H2SO4 Na2SO4 + H2O + CO2
Chemical properties of H2SO4 • Concentrated H2SO4 • As an oxidizing agent • Cu + 2H2SO4 CuSO4 + SO2 + 2H2O • C + 2H2SO4 CO2 + 2SO2 + 2H2O • As a dehydrating agent • Reaction with HX • 2HBr + H2SO4 Br2 + SO2 + 2H2O • 8HI + 2H2SO4 4I2 + H2S + 4H2O
Uses of sulphuric(VI) acid • Manufacture of detergents, dyestuffs, polymers, fibres, paints, fertilizers
Test for sulphate(VI) ions • Can be tested by adding a solution of BaCl2 acidified with dil. HNO3 • Ba2+ + SO42- BaSO4, a white ppt. • Note: • Ba2+ +CO32- BaCO3 • Ba2+ +SO32- BaSO3 • BaCO3 + 2HNO3 Ba(NO3)2 + H2O + CO2 • BaSO3 + 2HNO3 Ba(NO3)2 + H2O + SO2