Solutions to Worksheet on Groups 16 and 17

a. An element which at room temperature is a black solid in equilibium with a violet vapour.

Iodine, I₂.

b. The main product of the reaction of the second element in group VI with the most electronegative element of group VIII.

Sulphur hexafluoride, SF₆, (with traces of S₂F₁₀)

c. A compound of three elements (at least one of which is from groups 16 or 17) that contains an 8 membered ring.

(SF)₄N₄, S₄(NH)₄, S₇NH, (PCl₂)₄N₄ are all possiblities, all contain at least one element from groups VI or VII.

d. A colourless liquid that produces iodic and hydrofluoric acids when reacted with water.

Iodine pentafluoride, IF₅:

e. An element with no stable oxides at room temperature.

Bromine, Br. Those that are known are only stable at very low temperatures.

A is a solid that decomposes at -30ºC to give B, a yellow green gas and C, a cherry-red liquid. When C is treated with ammonia in an organic solvent, D, a yellow crystalline solid is obtained. D explodes when struck with a hammer, or when heated in a closed, strong container resulting in E, a colourless, odourless unreactive gas and F, a yellow crystalline solid that does not explode when struck with a hammer or anything else. When F is heated it melts a little over 100ºC to give a fluid red liquid but as the temperaure is increased further the colour darkens and the liquid becomes very viscous. At an even higher temperature the liquid becomes runny again and boils producing a flammable gas that burns with a blue flame, the product of combustion being G. When F is treated with B the first product is H a yellow liquid, which when treated with more B produces C. When G is mixed with air and passed over heated vanadium pentoxide I is produced with reacts violently with water to give a very strong acid J. Most of the above substances, notable exceptions being E and F, have strong, unpleasant smells and are poisonous.

      
              SCl4 ---> Cl2 + SCl2
               A        B      C
      
              6SCl2 + 4NH3 ---> S4N4 + 12HCl + 1/4S8 
                                 D              (F)
      
              2S4N4 ---> 4N2 + S8
                          E    F
      
         S8(s) ---> S8(l) ---> S (l) ---> S8(l) ---> S8(g) ---> S4(g)
      
              S8(g) + 8O2(g) ---> 8SO2(g)
                                   G
      
              S8 + 4Cl2 ---> 4S2Cl2       
      
              S2Cl2 + Cl2 ---> 2SCl2
                               H       
                        V2O5
              2SO2 + O2 ---> SO3   
                              I                    
      
              SO3 + H2O ---> H2SO4
                              J 

(C) H.J Clase 1998 - Updated 1999.03.23