Group 7: Halogens

Read our general notes on Risk Assessment

Hi, I was wondering if you could tell me what happens in experiments 6.6 and 6.7 involving chlorate(I) and chlorate (V) ions with iron(II) and iodide ions respectively in the Nuffield textbook. Thanks.

Corrie writes ...
 
In Expt. 6.6 chlorate(I) ions act as an oxidising agent, oxidising Fe²⁺ to Fe³⁺. This should produce a slight change in colour as Fe²⁺(aq) is very pale green, almost colourless, and Fe³⁺(aq) will be a pale yellow-brown here. The half-equations equations are:
 
Oxidation: Fe²⁺ -> Fe³⁺ + e^-
Reduction: ClO^- + H₂O + 2e^- -> Cl^- + 2OH^-

 
Overall: 2Fe²⁺ + ClO^- + H₂O -> 2Fe³⁺ + Cl^- + 2OH^-

 
In Expt.6.7 all the halates(V) are good oxidising agents and oxidise Fe²⁺ to Fe³⁺ in a similar way. For example:
 
6Fe²⁺ + ClO₃^- + 6H⁺ -> 6Fe³⁺ + Cl^- + 3H₂O
 
Chlorates and bromates oxidise iodide ions to iodine, so a brown colour will appear.
 
For example: 6I^- + ClO₃^- + 6H⁺ -> 3I₂ + Cl^- + 3H₂O
 
Iodate reacts with iodide ions to produce iodine and water:
 
5I^- + IO₃^- + 6H⁺ -> 3I₂ + 3H₂O
 

Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website. For further guidance see our tutorial on Risk Assessment.

back to Group 7: Halogens

---

Rate this page or react
Share your views on this page, 0 ratings so far

---

updated: 11 June 2007