Hi Geeks,
What is the produce of reaction between iodine and Potassium metabisulfite (in a water solution) ???kavu - 5-10-2011 at 22:14
Metabisulfite is unstable in aqueous solution and reacts with water to form hydrogen sulfite:
K2S2O5 + H2O → 2 KHSO3
Potassium hydrogen sulfite and iodine then undergo a redox reaction to yield potassium hydrogen sulfate and hydroiodic acid:
KHSO3 + I2 + H2O → KHSO4 + 2HI
This is more or less the expected reaction in acidic aqueous solution. If you hope to end up with potassium iodide a basification (KOH or other
potassium base) is needed to convert HI to KI. It should also be noted that HI is a weak acid and a fair share of it leaves the solution rather than
dissociates, lowering the yields.
[Edited on 6-10-2011 by kavu]rstar - 5-10-2011 at 23:20
It should also be noted that HI is a weak acid
[Edited on 6-10-2011 by kavu]
Thanks for the equation, and HI is not a weak acid, it is very strong acid, even more stronger than HCl
I guess it helps to define 'acidity' and what one think of as a strong acid. I could argue both cases for HI.
Any of the conventional definitions will mean that you lose the argument. A definition that makes HI look like a weak acid (in water) will get laughed
at. kavu - 6-10-2011 at 12:11
HI is undoubtedly a strong acid in aqueous solution with a staggering pKa of -10 at room temperature. It was purely my mistake to mix HI and HF