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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Sophia7X on October 17, 2012, 08:24:45 PM

Title: Why does Fe and Cl2 form FeCl3 instead of FeCl2?
Post by: Sophia7X on October 17, 2012, 08:24:45 PM

The oxidation potential for Fe--> Fe+2 is higher than Fe--> Fe+3 so wouldn't forming FeCl2 be more spontaneous than FeCl3?

Title: Re: Why does Fe and Cl2 form FeCl3 instead of FeCl2?
Post by: renjianan on October 18, 2012, 12:48:06 AM

Because the ΔH (enthalpy of combustion) of forming FeCl3 is higher than forming FeCl2. It means FeCl3 is more stable in thermodynamic than FeCl2.

Title: Re: Why does Fe and Cl2 form FeCl3 instead of FeCl2?
Post by: Borek on October 18, 2012, 04:07:23 AM

Quote from: Sophia7X on October 17, 2012, 08:24:45 PM

The oxidation potential for Fe--> Fe+2 is higher than Fe--> Fe+3 so wouldn't forming FeCl2 be more spontaneous than FeCl3?

As long as FeCl₃ formation is "spontaneous enough" it doesn't matter much - reaction won't stop half a way, unless there are serious reasons (like not enough chlorine) to do so.