Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: mizzle on October 16, 2009, 10:03:36 PM

Title: Barium chloride and sulfuric acid...
Post by: mizzle on October 16, 2009, 10:03:36 PM

I have a question regarding the reaction of aqueous Barium Chloride and aqueous Sulfuric Acid...

I know that

BaCl2 (aq) + H2SO4 (aq) ---> BaSO4 (s) + 2HCl (g)

I was wanting to find the standard free energy change associated with this reaction...

but I cannot find a G value for BaCl2 at all...

I need to find if this reaction is spontaneous... I think that it is, because it forms a precipitate with no added
external influence... but I don't know for sure.

Help me?

Thanks!

Title: Re: Barium chloride and sulfuric acid...
Post by: Schrödinger on October 16, 2009, 10:07:39 PM

Any reaction that occurs at a temperature is definitely spontaneous at that temperature.

I didn't get you when you said G value for BaCl₂. What does it signify?

Title: Re: Barium chloride and sulfuric acid...
Post by: mizzle on October 16, 2009, 10:10:54 PM

Hi Schrodinger :)

I meant gibbs free energy value, G :D

Title: Re: Barium chloride and sulfuric acid...
Post by: Schrödinger on October 16, 2009, 10:21:02 PM

There's no such thing as (https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fwww.forkosh.dreamhost.com%2Fmimetex.cgi%3F%7B+%5CDelta+G+%7D&hash=6f092a20a2af142deff5196e84e7edef7e6d65c3) for a compound. You must calculate it for the entire reaction as such.

Title: Re: Barium chloride and sulfuric acid...
Post by: mizzle on October 16, 2009, 10:52:05 PM

Um,

Isn't there a standard G for every compound?

Title: Re: Barium chloride and sulfuric acid...
Post by: steak on October 16, 2009, 11:09:50 PM

 There is a standard :delta: G of formation for every compound.  The standard :delta: G of formation for BaCl₂ is -858.6 kJ/mol. 

Title: Re: Barium chloride and sulfuric acid...
Post by: mizzle on October 16, 2009, 11:13:37 PM

Hi Steak,

Where did you find that value?

Title: Re: Barium chloride and sulfuric acid...
Post by: mizzle on October 16, 2009, 11:15:24 PM

Hi again,

I really think the reaction between Barium Chloride and Sulfuric Acid is spontaneous... but if I use the value given to me
by Steak, I get that  :delta:G is positive, which would indicate that the reaction is nonspontaneous...

Ugh... does anyone know this answer?

Title: Re: Barium chloride and sulfuric acid...
Post by: steak on October 16, 2009, 11:16:06 PM

That's the enthalpy of formation,  :delta: H. my bad.  it was on wikipedia

Title: Re: Barium chloride and sulfuric acid...
Post by: steak on October 16, 2009, 11:33:30 PM

To find the  :delta: G standard for barium chloride....
    :delta: G standard =  :delta: H standard - T  :delta: S standard       

(Those values, except T, are here----> http://www.statemaster.com/encyclopedia/Barium-chloride)

Calculate room temperature in K and use that for the T variable.  The  :delta: G of formation value that you receive can be used to calculate the  :delta: G of the reaction.  I'm certain it's a spontaneous reaction.

here's a movie----> http://genchem.chem.wisc.edu/lab/CCA/MVHTM/H2SO/H2SOBACL.HTM


p.s.  when calculating the  :delta: G for the reaction, make sure you're doing....
   (summation of :delta: G standard for products) -  (summation of :delta: G standard for reactants)