Core Periodicity: Chemical Properties
Slide 10 of 31
Reactions and Reactivity of the Halogens
1. With the halogens the reactivity decreases going down the group.
–Fluorine is one of the most reactive substances known:
–2F2(g) + 2H2O(l) ® 4HF(aq) + O2(g)  DH = -758.7 kJ.
–The reaction between chorine and water produces hypochlorous (chloric(I)) acid (HClO) which is the main ingredient in the disinfectants used in pool water:
–Cl2(g) + H2O(l) ® HCl(aq) + HClO (aq)
–Chlorine water and bleach will give off bubbles of oxygen if they are left in sunlight owing to the decomposition of the chlorate(I) ions:
–ClO-(aq) ® Cl-(aq) + O2 (g)
–This oxygen is what is used in the oxidation processes chlorine water/bleach engage in.
–Bromine dissolve slightly in water; and also bromine-water when exposed to light liberates oxygen
–2Br2(l) + 2H2O(l) ® 4HBr(aq) + O2 (aq)
–Iodine also dissolves in water but only slightly.
–(Hydrogen halides are all strong acids with the exception of HF. See Bonding: Intermolecular Forces)