Sciencemadness Discussion Board

WTH have i made now ?

rstar - 7-10-2012 at 08:58

First of all don't ask me the amount of reactants i've added, i did not measure em out.


Here's wat i did:

1= boiled about half-cup water in the beaker
2= added a chunk of elemental Iodine to it
3= then, i added Sodium bicarbonate to it.

the solution turned red-yellow, i kept on adding NaHCO3 (to make it colourless :D) but it just didnt work.

finally i stopped adding nahco3 , but the final solution was still red. and then, i kept it in a covered testube,

and now (after about 10 hours) i can see some orange yellow stuff crystallizing out on the sides and bottom of testube.

now WTH is that ??

blogfast25 - 7-10-2012 at 09:33

Assuming you were trying to convert I2 to iodide, your base (NaHCO3) was probably not strong enough. You're left withsome I2, some NaI and some NaI3.

querjek - 7-10-2012 at 10:09

Did you use tap water or distilled?

rstar - 8-10-2012 at 00:56

boiled tap water :D

this is wat i expected:
1= NaHCO3 on heating will decompose to Na2CO3. this appears by the bubbling out of gases(CO2)

2= Na2CO3 +I2 --> NaI + NaIO3 + CO2 (more bubbling)

i hv done this experiment before some months, and was perhaps successful earlier. but this time it gave unexpected results :o



[Edited on 8-10-2012 by rstar]

rstar - 8-10-2012 at 05:56

I has been more than 24 hrs now, and i think, a little bit of more stuff crystallized out.
no change in the colour of solution, still bloody red

i think to upload a picture of it after i borrow the better camera from my sister :)

woelen - 8-10-2012 at 23:02

You made nothing really special.

NaHCO3 is a very weak base. Your iodine partially reacted.
Part of the NaHCO3 looses CO2 in the hot water:

2HCO3(-) --> CO2 + H2O + CO3(2-)

The CO3(2-) is a somewhat stronger base. It reacts with water:

CO3(2-) + H2O <---> OH(-) + HCO3(-)

Iodine reacts with OH(-):

I2 + 2OH(-) --> I(-) + IO(-) + H2O

More iodine reacts with I(-):

I2 + I(-) --> I3(-), this has a red/brown color in aqueous solution.

On cooling down, Na2CO3 crystallizes and inside these crystals, which mainly consist of Na2CO3.10H2O, small amounts of I3(-) are trapped, giving them the orange/red color.

[Edited on 9-10-12 by woelen]

rstar - 9-10-2012 at 01:42

Wonder-full :D
So, that means i havent made enough NaIO3, nd the crystals r not naio3 ?

woelen - 9-10-2012 at 09:51

I assume that you used much more NaHCO3 than I2. So, indeed I expect you mainly made Na2CO3, with some I(-), I3(-) and also IO3(-) trapped in the crystals.

If you tell more about the amounts, used in the experiments (e.g. specify how many grams or milligrams you used of each of the chemicals), then I can tell more about your results, but given the observations, for now I assume that you mostly made Na2CO3.

elementcollector1 - 9-10-2012 at 10:32

On a side note, does this really lead to pure Na2CO3? One would think bicarbonate would still be present in significant amounts.