[Tflarr]

Hi, I'm kind of new to this so I hope someone can help me. This is my problem:
I'm doing some tests on enthalpy and I'm at the point of doing the calculations but I have no idea what specific heat capacity I have to use.
I have used 1M HCl, 2M HCl and conc HCl in a reaction with coper (II) carbonate.
Some people have told me that I just need to use the general heat capacity of water for all of my calculations but further research has shown that the specific heat capacities of the solution used are needed?
I really need to know what to do and if I do need to use the specific heat capacity of HCl can someone tell me what they are for the 1M, 2M and conc please?

Many thanks in advance 

[enahs]

I would see that if through your schools library you have access to an Online Journal Subscription Service (This is fairly common actually, just ask a Library worker). And then see if you can get access to this Journal (I am not at school right now, so I do not have access to the full article either):
http://www.springerlink.com/content/l1196557656607j5/

I am surprised your professor did not tell you how to handle this situation? In truth, in general for basic stuff most people do just use that of water. But if you equipment is really good, doing such can introduce a lot of error.


If you can not get access to the information, either ask your professor, or use it of water. Have you covered anything in lecture about estimating heat capacities at various concentrations? Or perhaps your book or professor gave/gives you the value for concentrated HCl (or you can find that one online) and then you are to assume the relationship is linear between Conc HCl and no HCl (water), and extrapolate the Heat Capacity.

You can then also as an extra analysis concept take your most diluted solution and assume that the heat capacity of water is a good approximation. Assume you did that measurement perfectly. And then use that data to calculate the Heat Capacities for the other more concentrated solutions. After a rough estimate of those heat capacities; then substitute them back into the calculation in the normal method as the heat capacities of the different concentrations. This is just a slight improvement over using the heat capacity of water, and it should be made clear it is dependent on the first measurement that most likely approaches the heat capacity of water is accurate.


The point is, there are lots of options. I would just ask your professor what He/She wants.

[Tflarr]

Thanks for the advise.
The main problem with this experiment is that it's a project so the teacher basically said pick an experiment and do it, so me like a clever person picked one that I'm not particularly good at.
I'll definitely try your suggestions tho and hopefully I'll be able to figure it out. 

[ARGOS++]

Dear Tflarr;

Could this be anyway of a little help to you:

I found in a “little before yesterday” LANDOLT & BÖRNSTEIN:
(A standard “Book” for such properties.)

HCl  +  200 H₂O (=   1.0%w/w = 0.274 molar)  by 18°C  = 0.979    kcal kg^-1 °K^-1
HCl  +  100 H₂O (=   2.0%w/w = 0.548 molar)  by 20°C  = 0.9650         “
HCl  +    25 H₂O (=   7.5%w/w = 2.055 molar)  by 20°C  = 0.8787         “
HCl  +    10 H₂O (= 16.8%w/w = 4.603 molar)  by 18°C  = 0.749           “
(The same book up to date would give you much more!)
Interpolation should be possible, but how extrapolation works, - I don’t know.

I hope it gives you at least an Idea.

Good Luck!
                   ARGOS⁺⁺

[Tflarr]

Just want to say thanks for all the help so far, but I have another problem :s since I'm technically neutralizing the HCl would what I'm doing count as a molar enthalpy change of neutralization?