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Iodine clock reaction catalyst

I am using copper (II) sulphate solution as a catalyst for my chemistry coursework which is based on the Iodine Clock Reaction. Whilst carrying out the experiment, when am i supposed to add the catalyst in? :s

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Reply 1
Avatar for Holcomb
Holcomb
4
Original post by nm3
I am using copper (II) sulphate solution as a catalyst for my chemistry coursework which is based on the Iodine Clock Reaction. Whilst carrying out the experiment, when am i supposed to add the catalyst in? :s


you obviously add it before the chemical that starts the reaction, and if you are doing the clock reaction with persulfate and iodide ions, copper (II) sulfate doesnt work. Copper (II) sulfate reacts with the iodide ions before persulfate is added, a dirty brown precipitate is formed
(edited 12 years ago)
Original post by Holcomb
you abviously add it before the chemical that starts the reaction, and if you are doing the clock reaction with persulfate and iodide ions, copper (II) sulfate doesnt work. Copper (II) sulfate reacts with the iodide ions before persulfate is added, a dirty brown precipitate is formed


erm no your wrong mate, it does work, as i used it for this same cw and it worked fine, no pervcipitate formed
Reply 3
Avatar for Holcomb
Holcomb
4
Original post by master_blaster66
erm no your wrong mate, it does work, as i used it for this same cw and it worked fine, no pervcipitate formed


did you do the clock reaction with persulfate and iodide?
Reply 4
Avatar for Holcomb
Holcomb
4
Original post by nm3
I am using copper (II) sulphate solution as a catalyst for my chemistry coursework which is based on the Iodine Clock Reaction. Whilst carrying out the experiment, when am i supposed to add the catalyst in? :s


so did you try copper(II) sulphate as the catalyst? did it work?
Original post by Holcomb
so did you try copper(II) sulphate as the catalyst? did it work?


yep it did work, i used 3 catalysts which were copper sulphate Ironsulphate and Iron chloride. they all worked
Original post by Holcomb
you obviously add it before the chemical that starts the reaction, and if you are doing the clock reaction with persulfate and iodide ions, copper (II) sulfate doesnt work. Copper (II) sulfate reacts with the iodide ions before persulfate is added, a dirty brown precipitate is formed


It depends on which mixture you added the catalyst to.

You've got two beakers, one contains the potassium iodide/iodine (whatever you used) and the other has the reactant that eventually causes the colour change (mine was hydrogen peroxide). Before mixing, you need to add the catalyst to the beaker that does not contain the potassium iodide.

When I added the copper (II) sulfate to the potassium iodide beaker, an exothermic reaction occured, and the brown percipitate did form.. but when I switched it round, and added it to the other, it worked just fine!

You've really got to fiddle with the order you put the reactants in. Its the most annoying part of the iodine clock reaction..
Original post by Holcomb
so did you try copper(II) sulphate as the catalyst? did it work?


It does work :wink:
Reply 8
Avatar for Holcomb
Holcomb
4
Original post by TheStudent.
It depends on which mixture you added the catalyst to.

You've got two beakers, one contains the potassium iodide/iodine (whatever you used) and the other has the reactant that eventually causes the colour change (mine was hydrogen peroxide). Before mixing, you need to add the catalyst to the beaker that does not contain the potassium iodide.

When I added the copper (II) sulfate to the potassium iodide beaker, an exothermic reaction occured, and the brown percipitate did form.. but when I switched it round, and added it to the other, it worked just fine!

You've really got to fiddle with the order you put the reactants in. Its the most annoying part of the iodine clock reaction..


I apolagise for giving wrong information :biggrin: but I thought of putting the copper sulfate in the other beaker which contained the persulfate ions and no iodide, but again when you pour the beaker with the persulfate and copper sulfate into the beaker containing the iodide, the copper sulfate would react with the iodide again wouldn't it? Do you know why this doesn't happen?
Reply 9
Avatar for Holcomb
Holcomb
4
Original post by master_blaster66
yep it did work, i used 3 catalysts which were copper sulphate Ironsulphate and Iron chloride. they all worked


Initially, did you put the catalyst into the mixture containing iodide or the one containing persulfate??
Original post by Holcomb
I apolagise for giving wrong information :biggrin: but I thought of putting the copper sulfate in the other beaker which contained the persulfate ions and no iodide, but again when you pour the beaker with the persulfate and copper sulfate into the beaker containing the iodide, the copper sulfate would react with the iodide again wouldn't it? Do you know why this doesn't happen?


No its cool! I just thought **** it, if it doesn't work in this beaker, let me try in the other before giving up.. and eureka, it worked :smile:

I can understand the logic behind what you're saying, but it just doesn't react with the iodide, no idea why..

I had sooooooo many issues with the order the reactants were placed in :colone: at one point, having wasted several hours banging my head against the wall, I was getting so frustrated when the mixture would instantly turn blue-black when I added starch to the beaker containing potassium iodide :colondollar:
Original post by TheStudent.
No its cool! I just thought **** it, if it doesn't work in this beaker, let me try in the other before giving up.. and eureka, it worked :smile:

I can understand the logic behind what you're saying, but it just doesn't react with the iodide, no idea why..

I had sooooooo many issues with the order the reactants were placed in :colone: at one point, having wasted several hours banging my head against the wall, I was getting so frustrated when the mixture would instantly turn blue-black when I added starch to the beaker containing potassium iodide :colondollar:


im finally done with my cw, i gave my final complete coursework in today, now fingers crossed.
have you done the analyisis and evaluation yet?
Original post by master_blaster66
im finally done with my cw, i gave my final complete coursework in today, now fingers crossed.
have you done the analyisis and evaluation yet?


Writing my evaluation up as we speak, and then i'm all done :biggrin: how many pages is yours, I think i've gone overboard with mine :colondollar:
Original post by TheStudent.
Writing my evaluation up as we speak, and then i'm all done :biggrin: how many pages is yours, I think i've gone overboard with mine :colondollar:


my analysis was only 4 pages :/..and evaluation was 8...wbu
Original post by master_blaster66
my analysis was only 4 pages :/..and evaluation was 8...wbu


Woops meant, how many pages is your whole coursework? mine stands at 40 pages + bibliography
Original post by TheStudent.
Woops meant, how many pages is your whole coursework? mine stands at 40 pages + bibliography


not too long it was 43 pages including 8 graphs, but note my tables took a whole of only 2 pages, my mates on 80 pages LOOL.
ermm i dont have no bibliography lol
Reply 16
Avatar for bluemax
bluemax
16
Original post by Holcomb
you obviously add it before the chemical that starts the reaction, and if you are doing the clock reaction with persulfate and iodide ions, copper (II) sulfate doesnt work. Copper (II) sulfate reacts with the iodide ions before persulfate is added, a dirty brown precipitate is formed



even if the copper ions react, its okay i guess because a catalyst does participate in a reaction in order to speed it up but it should remain chemically unchanged at the end of the reaction.
Original post by master_blaster66
not too long it was 43 pages including 8 graphs, but note my tables took a whole of only 2 pages, my mates on 80 pages LOOL.
ermm i dont have no bibliography lol


Phewwwww! I wasn't sure whether i'd written too much, or if the majority of people in my class were simply being lazy :biggrin:

Okay, maybe 80 is a stretch too far LOL. I do know someone whos handrawn 42 graphs though :biggrin:
Original post by bluemax
even if the copper ions react, its okay i guess because a catalyst does participate in a reaction in order to speed it up but it should remain chemically unchanged at the end of the reaction.


Yehh I tried to leave the beaker on the side when the percipitate formed, but because of it, the colour change wouldn't occur.. so couldn't exactly measure the rate of the reaction
Original post by master_blaster66
not too long it was 43 pages including 8 graphs, but note my tables took a whole of only 2 pages, my mates on 80 pages LOOL.
ermm i dont have no bibliography lol


Pretttyyy sure you need a bibliography for OCR B salters.. its on the mark scheme anyways. If you've copied and pasted graphs.. pictures.. information (even if its not word for word) then you need to say where you've got it from.

Like, when working out the arrhenius equation, you need to know what it is (cue source), what the gas constant is (cue source).. good luck! :biggrin:

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