# Redox Relapse

1. May 18, 2005

We need to know what the products of KI + H2O in ionic form.

2. May 18, 2005

### dextercioby

The reaction should be

$$2KI+H_{2}O\rightleftharpoons K_{2}O+2HI$$

which in ionic form

$$2K^{+}+2I^{-}+H^{+}+OH^{-}\rightleftharpoons 2K^{+}+O^{2-}+2H^{+}+2I^{-}$$

I don't see any redox here...

Daniel.

3. May 18, 2005

THe labis on oxidation reduction. It says that ppt turns pink in the presence of hyrdroxide ions and the starch will turn black/blue in the presence of molecular iodine. We figured that this meant that in the equation that this meant in the products their will be a hydroxide ions and an I molecule. We thought that the answer you gave us was right but our teacher said that we were closer when we showed him KI + H2O--> OH + K + I2 + H

4. May 18, 2005

### dextercioby

Yes,i didn't think of that option.There it is.Can u find the coefficients by accomplishing the electron transfer ?

$$aK^{+}+bI^{-}+cH^{+}+dOH^{-}\rightleftharpoons eK^{+}+fOH^{-}+gI_{2}+h H_{2}\uparrow$$

Daniel.

5. May 18, 2005

yeah we should be able to, um what are the a,b,c,d,e,f,g for?

6. May 18, 2005

### dextercioby

Coefficents,like 1,2,1/2,3/2,3.

So who's getting oxidated and who's getting reduced...?

Daniel.

7. May 18, 2005

umm I havent done it yet;P

8. May 18, 2005

### dextercioby

It's not funny.If u haven't done redox reactions in school,why do you bother with this problem...?

Daniel.

9. May 18, 2005

### DrMark

Me thinks something is a miss here. Was it hydroxide or peroxide ?

10. May 18, 2005

it was hydroxide

11. May 19, 2005

### DrMark

OK what is ppt ?

12. May 19, 2005

### Staff: Mentor

13. May 22, 2005

the ppt is phenalthailene...and the reaction is K + I + H2O --> KOH + I + H

14. May 23, 2005

### GCT

Alright, I would imagine that this is a simple dissociation reaction, $$KI_{(s)}+H_2O \rightarrow K^{+}_{(aq)}+I^{-}_{(aq)}$$

The starch test will not work without molecular iodide however, I2. You'll need both I2 and I-, for the iodine complex involving I3-.

15. May 24, 2005

### DrMark

OK I'm highly dyslexic, but did you mean phenolphthalein ? There still is something a miss here (like what would oxidize the I-).

16. May 24, 2005

### GCT

potassium reacts with water??? Never actually encountered this before, I though it would be a spectator ion. I've read about this and it seems that KI is dissolved in water to provide I-, subsequently I2 is added to form I3-, which can form complexes with starch conterparts to form a colored solution.

I'm somewhat sensitive about the way some high schools deal with redox reactions as at times they are completely misleading and inaccurate. I've had a post in my forum a couple of months ago regarding a high school chemistry competition of which one of the answers provided turned out to be completely inaccurate. I couple of students decided to seek help online for references and quotes.