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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Professor 0110 on February 10, 2010, 03:27:00 AM

Title: Question about an exothermic reaction
Post by: Professor 0110 on February 10, 2010, 03:27:00 AM

Hi all,

Suppose I heat Hydrochloric Acid and Iron in a test tube, thereby causing the chemical formation of Iron Chloride. Hydrogen gas is released during the process. I know that heat is given off, but is the release of hydrogen gas another valid piece of evidence that an exothermic reaction is taking place?

Any replies to this question will be appreciated! :D

Thanks. 

Title: Re: Question about an exothermic reaction
Post by: Borek on February 10, 2010, 04:17:33 AM

Quote from: Professor 0110 on February 10, 2010, 03:27:00 AM

is the release of hydrogen gas another valid piece of evidence that an exothermic reaction is taking place?

No.

Title: Re: Question about an exothermic reaction
Post by: cpncoop on February 10, 2010, 07:28:30 AM

Release of gas usually is an endothermic process.  If you look at the equation for calculating Free Energy:

 :delta:G =  :delta:H - T :delta:S

Going from a liquid to a gas increases entropy (S), which therefore lowers  :delta:G... Hope this helps,