We will restrict our studies to the
three middle halogens (Cl2-I2).
A halogen HIGHER UP in the periodic table will DISPLACE one LOWER DOWN in table from a solution.
–In general: X2 + 2Y- ® 2X- + Y2
–Chlorine will displace any
halide ion below it in the table from a solution.
•Cl2 (aq) + 2Y-(aq) ® 2Cl-(aq) + Y2 (aq) Where Y- = Br- or I-
–Bromine will displace iodide ions from a solution.
•Br2 (aq) + 2I-(aq) ® 2Br-(aq) + I2 (aq)
–Evidence for displacement comes from changes in
the appearance of the reaction mixture which you observed in
the lab.
–So, of the three, chlorine is the most reactive,
followed by bromine and then iodine.