Analytical Chem report #7 - Antacid

Has anyone started yet? I did one data sheet to find the molarity of the HCl. That was no problem. Now I have a 2nd sheet to calculate the antacid consuming capacity. We don't need to calculate anything further than that do we?
There were quite a few calculations needed to get that, but I didn't know if we needed to calculate any type of error between each trial. The lab manual did not specify that we did. I may just email him to be sure though.

What was your RSD like? Mine came out to like 17 ppt this time, and for some reason my calculations for my Molarity are coming out around .045 instead of .10. Is the mol ratio of HCL to Na2CO3 greater than one? Also, was there anything written on our standardized Na2CO3 bottles? The only thing I have written down is that the company was Thorn Smith...

My RSD came out to 3.12 and my molarity was .09088. This is the lowest RSD I have had. The equation is
2 HCl + Na2CO3 -> 2 NaCl + H2O + CO2. The only thing I have written down for the Na2CO3 is that the purity is 100.03%.

Alright well fixing my molarity equation they are coming out closer to .10. As for the antacid part of the lab report, I have no idea where to begin with the calculations. I don't know if it's easy enough for someone to explain over the forums, so be prepared for me to pick your brain monday Stacy

You have to do the second part as a back titration calculation. Use the equation I posted along with
HCl + NaOH -> NaCl + H2O

Use Total moles of HCL - moles of HCl that react with NaOH(from buret readings) = moles HCl that react with antacid

The goal is to find the acid consuming capacity of .100 M HCl that a 5 mL dose of antacid will neutralize.

5.0 mL x mL of .100 M HCl that will neutralize / mL sample used (use density to convert your grams to mL)

Mine all came out to about 267-268 mL that will neutralize a 5mL dose. I had the extra strength.

Na2CO3 (Primary Standard Grade): Sodium Carbonate, Factor Purity 7 - 78, Dry 1 hr @ 140 C, Thorn Smith, 1023 Troy Court, Troy MI 48084

My notes are a little different than Stacy's. I wonder about both our Factor Purity #'s. Nikki has same as Stacy. 100.03%
7-78 could be July, 1978.
This is guaranteed to be a fun lab report. not.

I do remember that one of the bottles did not have a purity on it - it was so faded it could not be seen. I think they were identical though, so they should both be 100.03%.

As I am writing my conclusion, I am now not sure I used the correct equation to calculate the acid neutralizing capacity. My samples had 400 mg of Mg(OH)2 and 400 mg Al(OH)3 in them. I see those equations listed in the lab manual, but I am not sure which one I am supposed to use. I originally used the CaCO3 equation.

What were your samples comprised of? I know they were all different depending on the strength.

Maximum strength was 3 antacids:
1) Aluminum hydroxide equivalent to dried gel USP 400 mg,
2) Magnesium hydroxide 400 mg
3) Simethicone 40 mg.
Aluminum and Magnesium are strong bases - I think they are consumed at the same time, but I think you should get 2 equivalence points on a titration curve.
I'm really worried about the calculations. I don't have any idea where simethicone fits in - going to google for help.
Simethicone does not appear to be antacid - it's anti-foaming.
This may be my re-do experiment. (I think I say that each time.)

The calculations are a little confusing. Maybe we can go chat with him after class tomorrow? I know it helped a lot on the other lab.

Count me in.

I sent him another email with my Excel sheet attached. I told him that I cannot meet with him tomorrow and asked if he would look over my calculations and let me know if I am doing them right. Hopefully he will respond!

I hope he responds. It would be kind of you to post his comments.
Google turns up this lab. They used tablets instead of liquid, but it's basically the same experiment.
http://homepages.ius.edu/DSPURLOC/c121/week12.htm

I'm lost on how do the final calculation. I found the moles HCL that react w/ antacid, but where do I go from there? The equation he gave us is 5.0 ml (sample) X (ml 0.100mHCL that sample will neutralize)/(ml sample used). I have no idea how to get the top or bottom of the fraction. What is the ml sample used? Where do I use my moles HCL that react w/ antacid?

I am not that far, but the Density might help. 1.17 g/ml for Max strength.

5.0 ml X mL 0.100M HCl that will neutralize (find moles from the back titration, then calculate how many mL of .100 M HCl will give you that amount of mols)/mL sample used (used density to convert grams to mL)

This is what he said in lab and I wrote it down.

How do you convert the density to ml? They didn't give us a formula weight, so how exactly do you get rid of the grams?

done on this for now. resume other studies.
maybe take the original grams of the sample X grams/ml (density)???

I used the grams of sample I had and multiplied by 1 ml/1.172 grams(density). That will give you mL for each sample.

I got 401.18 for my acid consuming capacity. Seems pretty high, but that's what I got. Guess I'll get cranking on that conclusion.

My RSD was only 1.5, so I guess I was awesome at my titrations!

Did anyone write down the lot number for the 12.1 M HCL? and the percentage......

I will get the correct HCL info, hold on ...

Kyle, it sounds like you got yourself in a loop & you are multiplying something that you already divided by.
I am struggling real hard to understand the pH at equiv point for weak acid strong base. The additional prob set worksheet - 1st problem. did anybody do that?

I am so close to getting it ...

HCl 12.1 M (concentrated) Hydrochloric Acid, Reagent ACS, Fisher Scientific, UN1789, A144S-500, Assay w/w minimum 36.5% - max 38%