Displacement Reactions Halogens/Halides

O

Ollie

Lab Technician
Hi guys,

I am attempting to set up a class practical for displacement using 0.1M KI, KBr and KCl mixing these with iodine solution, chlorine water and bromine water. However I am trying to test this before giving it out and I am not getting the desired reactions when mixing the chemicals together (the colour changes in the solutions). For example when mixing KI with the bromine water and chlorine water the solution is remaining colourless where it should theoretically be turning a redish. I have tried to remake my solutions at 1M for KI and I still cannot get the colour change to occur, does anyone know what I may have done wrong here? I have also tried this reaction with chlorine water in a 50/50 dilution with water but also without diluting it and I still can't get the reaction. I don't see what I could've done wrong here as I've followed all the steps given via the practical sheet and from CLEAPSS?
 
S

seebee

There should be no reaction with chlorine water, bromine water and iodine with potassium chloride.
Potassium bromide and chlorine water - yellow orange. no reaction with bromine and iodine water.
Potassium iodide - brown with chlorine water and yellow orange to brown with bromine water, no reaction with iodine water.
 
C

ClaireL

I know when we do it (and we don't add hexane, though I know we can), the non- bromine positive results are difficult to see- some use white spotting tiles so its an easier contrast to see, but if test-tubing, need paper behind it to see any differences..
 
V

Vic

Are you making the chlorine water fresh? What method are you using to make it?
Chlorine water must be made fresh and the chemicals you use to make it should also be relatively new. I personally prefer the bubbling of chlorine gas through water for the best chlorine water but you need training if you have not carried out this method before. The chlorine water should have a slight green tinge to it.
 
B

Baldilocks

The iodine solution for this, what does anyone use? We buy it in diluted in KI, but the old bottles of "iodine water" we've had since 2 chem techs ago were always much paler. Suspect she just diluted down the stock solution but not sure. We're thinking dilute down to 50/50 and test it. What do you all do?
 
B

Bert

Baldilocks said:
The iodine solution for this, what does anyone use? We buy it in diluted in KI, but the old bottles of "iodine water" we've had since 2 chem techs ago were always much paler. Suspect she just diluted down the stock solution but not sure. We're thinking dilute down to 50/50 and test it. What do you all do?
Click to expand...
I'm not much help I just dilute our stock by eye! I'm guessing 0.05M or a bit less, needs to be darker than apple juice but lighter than cola. Maybe about malt vinegar colour.
 
You must log in or register to reply here.
Top