2. General properties Group VIA (2:8:6) 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.

3. Range of sulphur compounds Chemical formulaeOxidation state S 2-, H 2 S-2 S8S8 0 SCl 2, S 2 O 3 2- +2 SO 2, SO 3 2-, H 2 SO 3 +4 SO 3, SO 4 2-, H 2 SO 4 +6

4. Burning of sulphur Sulphur burns with a dull blue flame to form sulphur dioxide, trace of misty sulphur trioxide are also formed. S + O 2  SO 2

5. 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 SO 3, which dissolves in water to form sulphuric(VI) acid, H 2 SO 4

6. Oxidizing properties of SO 2 2Mg + SO 2  2MgO + S 2H 2 S + SO 2  2H 2 O + 3S Aqueous SO 2  SO 3 2- (aq) 2MnO 4 - + 5SO 3 2- + 6H +  2Mn 2+ + 5SO 4 2- + 3H 2 O Cr 2 O 7 2- + 3SO 3 2- + 8H +  2Cr 3+ + 3SO 4 2- + 4H 2 O

7. Oxidizing properties of SO 2 Br 2 + SO 3 2- + H 2 O  2Br - + SO 4 2- + 2H + Dye + SO 3 2- + H 2 O  Dye-O + SO 4 2- + 2H +

8. Sulphuric(VI) Acid Contact Process S + O 2  SO 2 (or 4FeS 2 + 11O 2  2Fe 2 O 3 + 8SO 2 ) 2SO 2 + O 2  2SO 3 (450 o C, V 2 O 5 as catalyst) SO 3 + H 2 SO 4  H 2 S 2 O 7 (then H 2 S 2 O 7 + H 2 O  2H 2 SO 4 )

9. A flow diagram Purifier and drier Air Heat exchanger Catalytic chamber Absorption tower Purifier and drier Sulphur burner Air H 2 SO 4 store water 98% H 2 SO 4 c.H 2 SO 4 oleum drySO 2 +air SO 3

10. Chemical properties of H 2 SO 4 Dilute H 2 SO 4, a typical acid Zn + H 2 SO 4  ZnSO 4 + H 2 2NaOH + H 2 SO 4  Na 2 SO 4 + H 2 O CuO + H 2 SO 4  CuSO 4 + H 2 O MgCO 3 + H 2 SO 4  MgSO 4 + H 2 O + CO 2 2NaHCO 3 + H 2 SO 4  Na 2 SO 4 + H 2 O + CO 2

11. Chemical properties of H 2 SO 4 Concentrated H 2 SO 4 As an oxidizing agent Cu + 2H 2 SO 4  CuSO 4 + SO 2 + 2H 2 O C + 2H 2 SO 4  CO 2 + 2SO 2 + 2H 2 O As a dehydrating agent Reaction with HX 2HBr + H 2 SO 4  Br 2 + SO 2 + 2H 2 O 8HI + 2H 2 SO 4  4I 2 + H 2 S + 4H 2 O

12. Uses of sulphuric(VI) acid Manufacture of detergents, dyestuffs, polymers, fibres, paints, fertilizers

13. Test for sulphate(VI) ions Can be tested by adding a solution of BaCl 2 acidified with dil. HNO 3 Ba 2+ + SO 4 2-  BaSO 4, a white ppt. Note: Ba 2+ +CO 3 2-  BaCO 3 Ba 2+ +SO 3 2-  BaSO 3 BaCO 3 + 2HNO 3  Ba(NO 3 ) 2 + H 2 O + CO 2 BaSO 3 + 2HNO 3  Ba(NO 3 ) 2 + H 2 O + SO 2