1. Halogens

3. Physical Properties State at stp Atomic radius (nm) Bpt oC F2
Pale yellow gas
0.071
-188
Cl2
Pale green gas
0.099
-35
Br2
Red liquid
0.114 59 I2
Purple solid
0.133
184

4. Which Halogen is the best Oxidising Agent?
Potassium halide solutions
Cl-(aq) Brl-(aq) l-(aq)
Halogen dissolved in water
Cl2(aq), Br2(aq) I2(aq)
Write brief plan of investigation
Make predicted results table
Write up results & conclusion

5. Displacement Reactions
Cl-(aq)
Br-(aq)
I-(aq)
Cl2 (aq)
Yellow/ orange solution
Brown solution & black ppt
Br2 (aq)
No change
I2 (aq)

6. Chlorine displaces Br2 & I2
Cl2 + 2KBr → 2KCl + Br2
Cl2 is the oxidising agent
Cl2 + 2Br- → 2Cl- + Br2
Cl e- → 2Cl-
Cl2 + 2KI → 2KCl + I2
Cl2 + 2I- → 2Cl- + I2

7. Bromine displaces I2 Br2 + 2KI → 2KBr + I2 Br2 is the oxidising agent
Br e- → 2Br-

8. Halogens as Oxidising Agents
Cl2 + 2Br- → 2Cl- + Br2
Cl2 + 2I- → 2Cl- + I2
Br2 + 2I- → 2Br- + I2
Cl2
Br2 I2
Strongest oxidising agent
Oxidising Agents Accept Electrons-

9. Halogens as Oxidising Agents
Fluorine would displace all other halogens
F2 + 2CI- → 2F- + Cl2
F2 > Cl2 > Br2 > I2
Increase in oxidising power
Oxidising Agents Accept Electrons
X2 + 2e- → 2X-

10. Halides as Reducing Agents
The halide ions act as reducing agents
2X- → X2 + 2e-
Reducing Agents Donate Electrons F-
Cl-
Br- I-
Strongest reducing agent

11. Which Halide is the best Reducing Agent?
Solid sodium halides
NaCl (s) NaBr(s) NaI(s)
Concentrated H2SO4
Predictions
What products could be formed?

12. Possible Products The halide ions act as reducing agents X- → X2 ? -1
The sulphuric acid acts as an oxidising agent
H2SO4 →
SO2 ?
S ?
H2S ? +4 +6 -2

13. Results
Halide
Products
Observations
NaCl
NaBr
NaI

14. Halide
Reaction Products
Observations
NaCl
HCl
Steamy fumes
NaBr
HBr
Br2
SO2
Brown Fumes
Colourless gas
NaI HI I2 S
H2S
Black solid, purple fumes
Yellow solid
Smell of bad eggs

15. 1. Acid – Base Reactions All halides can act as bases
Bases accept H+ ions
NaX + H2SO4 → HX + NaHSO4
Base + acid → Hydrogen halide + salt
NaF + H2SO4 → HF + NaHSO4
Hydrogen halide produced via acid-base reaction with ALL halides

16. 2. Redox Reactions
Products of this stage depend on the reducing ability of the halide
Reducing Agents Donate Electrons F-
Cl-
Br- I-
Strongest reducing agent

17. Sodium Bromide NaBr Br- quite a good reducing agent H2SO4 → SO2
2H+ + 2e- + H2SO4 → SO2 + 2H2O
2Br- → Br2
2Br- → Br2 + 2e-
2Br- + 2H+ + H2SO4 → SO2 + 2H2O + Br2

18. Sodium Iodide NaI I- very good reducing agent H2SO4 → SO2
2H+ + 2e- + H2SO4 → SO2 + 2H2O
2I- → I2
2I- → I2 + 2e-
2I- + 2H+ + H2SO4 → SO2 + 2H2O + I2

19. Sodium Iodide NaI x 3 I- very good reducing agent H2SO4 → S
6H+ + 6e- + H2SO4 → S + 4H2O
x 3
2I- → I2 + 2e-
6I- → 3I2 + 6e-
6I- + 6H+ + H2SO4 → S + 4H2O + 3I2

20. Sodium Iodide NaI x 4 I- very good reducing agent H2SO4 → H2S
8H+ + 8e- + H2SO4 → H2S + 4H2O
x 4
2I- → I2 + 2e-
8I- → 4I2 + 8e-
8I- + 8H+ + H2SO4 → H2S + 4H2O + 4I2