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Ted Mooney, P.E. RET
Pine Beach, NJ

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Potassium iodide reaction with iron(III) chloride?

Q. I have no idea about the reaction of these two compounds. The only information I have is that a brown solution is formed.

Steve S. [surname deleted for privacy by Editor]
student - Malaysia
August 27, 2008

Hi, Steve. I'm happy to try to help, but not to do the disservice of doing your homework. So please write the left hand side of the equation, and I'll try to give you a hand with the right hand side.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 28, 2008

September 6, 2008

Hi,
3KI + FeCl₃ = FeI₃ + 3KCl
FeI₃ is brown.

Jason Rothman, Chemist
- Pomona California

Hi Jason,

How did you get the subscripted numbers in your post, please? Damned if I can find a way - no text formatting available on the submission page, and pasting from a formatted Word document destroys the subscripting format.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
September 18, 2008

September 18, 2008

Hi, Bill.

If you really wish to take the time, you can do subscripts, superscripts, bold, and italics... it's standard HTML of:

, , , or before the character(s) you want to modify and

, , , or to restore normalcy.

So Jason's first line is:

3KI + FeCl3 = FeI3 + 3KCl

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Chlorine is more reactive than iodine and will try to replace the iodine in the compounds. the equation is

2FeCl₃ + 2KI --> 2FeCl₂ + 2KCl + I₂

the net ionic equation is

[2I]^- + [2Fe]³⁺ --> [I₂] + [2Fe]²⁺

John callan
- Lawrenceville, New Jersey, USA
October 29, 2010

A. First answer (by the Chemist) is wrong; FeI₃ does not exist, this is a redox reaction, I₂ (or its complex KI₃ with KI) is the red/brown color.

David Liu
- Houston, Texas
November 19, 2015

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