Answers to Group 17 Practice Questions

Q1:  Iodine is reduced from +3 to +1 and chlorine is oxidized from -1 to 0 so it is redox. Because the same atom is not both oxidized and reduced, it is not disproportionation.


Q2: Given its atomic number, Oganesson will be directly underneath Astatine in the periodic table, so it will be darkest of the halogens (black) and will have a higher meltingand boiling point that astatine (solid at room temperature). Reactivity decreases going down the group, so Oganesson will be the least reactive of the halogens.


Q3: Initially the solution will be colourless. When colourless chlorine water is added, the solution will turn orange-brown as iodine is displaced. When cyclohexane is added the iodine will dissolve in this layer, showing a purple colour. This leaves chloride ions in the aqueous layer, and these will react with the added silver ions to produce a white precipitate of silver chloride.


Q4:      3Cl2(g) + 6NaOH(aq)  →  5NaCl(aq) + NaClO3(aq) + 3H2O(l)


Q5: (i) the precipitate suggests the halide ion is chloride or bromide. Adding chlorine water will cause a reaction with bromide ions, displacing bromine (an orange colour will appear in the solution) while no reaction will take place between chlorine water and chloride ions.

(ii)       Ag+(aq) + Br(aq)  → AgBr(s)                  

             Cl2(aq) + 2Br(aq)  → Br2(aq) + 2Cl(aq)