Analytical Chem report #9

Just wondering if anyone has graphed their curves for the lab we just did last week? My 2nd equiv. point is very obvious. My 1st is not. I did 3 trials and they all look the same pretty much. I have tried stretching out my graph, condensing my graph and I am still not sure exactly where the 1st one is. I think I have a 2 monoprotic acid mixture, but then again I am not positive. I guess I will show up early on Tuesday and have him look at my data. I took plenty of readings, so I don't think doing another trial will make a difference.

I didn't think I had hit any equivalence. Looks like I had a soft one that was not apparent.
Had to graph ΔpH before I saw it. Thank God, I was close to being done with this. (This was my nightmare - not getting it done.)
Weird that my pH meter gave me different readings for first & second trial. Guess I have to recalibrate between samples.
Good thing I am redoing on Tues.

The lab manual does not state what our RSD should be for this lab. If I use all 3 trials, mine is 21%. If I remove one trial it is still 13%. Anyone have any idea? I really don't want to mess this lab up since I did not ask to re-do it!

He responded to my questions but never gave a definitive answer on the RSD he is looking for. He did say that you cannot throw out any trials unless you Grubbs test and find that you can. My RSD is still coming out higher than I would like, but there is nothing I can do about it at this point. I think I will just give up and go with what I have!

I agree that you should. So he didn't give any indication of RSD? either he doesn't know or it can be kind of high, like the antacid one, our RSD's were higher than what we've normally seen, but its a relative thing anyways....

you know its kind of weird that we have to use all three trials but he really stressed that we need only two good trials..... eh... guess just for extra data..... or better data.... somethin like that.....

Yeah, I am wishing I only had my 1st 2 trials because my 3rd one is the one that is screwing everything up! Go figure!

yeah... this is real iffy.... so did yours turn out to be 2 monoprotic acids or a diprotic acid? I'm thinking mine is on the fence, The equivalences points are kind of spaced equally apart, but they defer by like .5ml to 1ml, is that within range? if so, i have a diprotic acid. AND if i do, then shouldnt the concentrations come out to be the same or real close? If I calculated two using the equivalence points as if it were two acids?

You only need 2 trials. He coerced me into not doing a third trial by showing me my first trial on his laptop, remember? Did he say something differently to you guys?

He told me that since I did all 3 trials, I could only get rid of one of them if it was statistically off (Grubbs test) or if there was a note in my lab manual that it was a rough trial (this was only for our first trial though). I am including all of them and have an RSD of 10.23. Without knowing what the standard RSD should be, I am hoping this is within his range, or at least close enough to not lose too many points. I think the biggest downfall of this lab is if you guess diprotic and it is really 2 monoprotics or vise versa.

I think mine is diprotic. My equivalence points are almost equal. He said in lecture that they would not give us 2 monoprotics that were even close to being equally spaced, so I am taking his word for it. Let's just hope I at least get this part right.

You only have to calculate one concentration for a diprotic since it is the same acid. For 2 monoprotics you have to calculate 2 concentrations.

with an SD for Experiment 8, SD is 22. Probably no need to figure RSD or anything else. Cant wait to start #9.
I wonder what happened in 8. Any ideas? Used almost exactly 1 ml more in the first trial.

Okay I believe I lost my paper for this lab so I desperately need some help. What exactly does he want us to calculate from these graphs?

Kyle, I'm not sure what he wants other than what is stated in the manual.
If that's what you lost, I can scan it & send it to you.

If you could that would save my life. I can't find that paper from my manual anywhere (I think Stacy stole it!)

Are our equivalence points just estimates from the graphs? We just compare the distance between the first and second to determine if its monoprotic or diprotic?

did you get it?

Yes you are the greatest <3

He wants the concentrations. You might be able to read my notes. If not, call me 779-6026
(and remember me at Christmas)

What exactly do we do an RSD of?

I got a concentration of ~.07 and .04 for mine. That means it is monoprotic, right?

I did not steal your paper! I wrote on your paper earlier today about how to calculate it though.

by the way, Kyle, if you had "B" we had the same acid. I got different concentrations (go figure, it's me)
0.04 and 0.05