hypervalent_iodine

47 minutes ago, beecee said:

 

I'm well aware of the controversy that Australia Day is to many indigenous people, and I have no objection to it being changed to a more appropriate date if that is what people want.

I also live in Sydney, at Maroubra, only a couple of kilometers from La-Perouse, a suburb with a large indigenous population, and count many indigenous people as friends.

Yes, the first Settlers did rape, pillage and Murder the local people, just as they did elsewhere, and that is something we should be sorry about...In fact one of our Labor Prime Ministers, did apologise in the Parliament a few years ago, at least with regards to the "Stolen Generation".

As a 100% Labor man through and through, I supported that totally.

Still Australia Day, whether on the 26th or not, is well worth celebrating, as in essence, it celebrates more then what some claim as "Invasion Day", it celebrates what being an Aussie truly is, and irrespective of politics, It's the aspect I'm proud of. 

I have also had the great honour of meeting imo, our greatest ever Prime Minister, one who also did much to unite indigenous Australia and the rest of us Imported variety Gough Whitlam along with Jim Cairns.

And also the following Prime Minister....

 

You’ll have to forgive me for not assuming you were overly aware of the very real horrors of our history after what you posted in the OP.

No one is saying it shouldn’t be celebrated, just that it should perhaps be done on a day that doesn’t utterly disrespect Indigenous Australians. Do you think First Nations people should just get over what happened to them because we said sorry in 2008? Should we not reinforce those words with actions with they were sciencerly meant? To me, and to many people, being Australian is (or should be) about being inclusive, welcoming and fair to all people. We don’t achieve that by ignoring our history and the damage colonisation has and continues to cause. 

23 minutes ago, StringJunky said:

Aye, we Europeans don't have a lot to be proud of on the geographical discovery front.

There's a lot of controversy around the date of Australia Day here, which is partly why I responded. It is meant to commemorate the landing of the first fleet, which was on Jan 26, but in doing so it alienates Australia's First Nations people. They call it Invasion day and consider it a day of mourning, since it is the date that coincides with the invasion of their home and murder of their ancestors by white European settlers. There is a push in recent years to have it changed to a different date, which is not unprecedented as it has historically been celebrated on several different dates. Most people don't seem to mind when it's held, which suggests it could easily be changed without much backlash. And why wouldn't you want to? Australia isn't exclusively a country of white people, and it doesn't hurt anyone to change the date to something a little more respectful and kind to our First Nations people. On the other hand, the PM, with the support of many right wing pundits, has decided to double down on Australia Day being when it is, forcing councils to move their citizenship ceremonies to be on Jan 26 and then sinking $6.7mill into making a replica of James Cook's ship, the Endeavour, and having it circumnavigate the country as part of the celebrations (something James Cook never did, by the way). 

Oof, what a very white washed and Euro-centric retelling of an extremely brutal history.

It won’t produce any gas AFIK, just calcium hydroxide and then calcium acetate. What’s wrong with just using baking soda and vinegar? You could add dry ice if you wanted a nice smokey  effect.

49 minutes ago, John Cuthber said:

This sort of thing?
https://en.wikipedia.org/wiki/Charged_aerosol_detector

The last time I looked they weren't very sensitive- but that's probably improved and they will be cheaper than MS.

Yes, those. I am not very familiar with them personally, but it seems like it would be workable for the OP. Thermo literature states that their current model can profile PEG quite well and quantify polyacrylic acid down to ppb levels in industrial cooling water samples.

7 minutes ago, John Cuthber said:

It's very water soluble, so extraction into a solvent won't work- pity, because that's ofte a very useful first step.

You could remove the water by simply boiling it off. The poly glycol will remain.

But, so will all the other stuff you find in swimming pools. Let's be polite and call it urea.

The urea would upset any attempt to identify the PAG by IR.

So IR is not going to get very far (and it's also not very sensitive)

The mixture of materials present is going to be complicated so it's probably best to try to unmix it before you do anything else.
The go-to method for sorting mixtures in the laboratory is chromatography.
As has been pointed out, this stuff is too involatile to try to GC it.

So we are looking at HPLC

There's no useful chromophore so UV detection's not going to work (not at ppm levels anyway).
So I think you are pretty much stuck with HPLC MS.

I hope you have plenty of money.

You can use use a Corona detector in tandem with HPLC, which would circumvent the need for a chromophore. Not sure if that would be cheaper than MS, but you’d need a decent amount of money either way I guess. 

48 minutes ago, studiot said:

Does it matter which alkene or which glyc , poly, -ol it is in this instance?

Would you want your child swimming in any of them?

https://orgchemboulder.com/Spectroscopy/irtutor/alkenesir.shtml

 

Though I would really like a specialist to come up with a significantly better suggestion,

I would also like more background information.

It matters if it is a single compound if they want to measure it at ppm levels, as stated in the OP.

Thank you for the tutorial in IR that you posted. As it happens, I use IR regularly, albeit for characterisation rather than quantification. In any case, I can’t for the life of me figure out why you have posted it here? It doesn’t refute anything that I have said wrt the suitability of IR for the OP’s stated intention. Moreover,  I would like to add that you are unlikely to see alkene stretches in this instance. These peaks are typically very weak, and would likely be obfuscated by OH peaks (if present), and the myriad of other peaks in there that would be there in greater number and thus have much higher absorbance.

I have to ask, why exactly are you being so stubborn on this point? You have been told by two people who work in chemistry that IR is not a good option in this instance, for the reasons stated. You stubborn insistence is confusing. I have in fact suggested another alternative, HPLC. You would need a particular type of detector to do it for these samples, but I cannot think of any other way to easily quantify aqueous solutions of PAG. 

@Mt21 you may also wish to ask your question at Chromatography Forum. It’s reasonably busy and has a lot of talented people there who specialise in quantification and the various pieces of equipment you might come across. I used to frequent there a lot when I worked in an analytical lab as a technician. 

4 hours ago, studiot said:

 

I think we are guessing as to the circumstances around the OP desire to measure these parameters.

One off or a future continued programme?

An individual or a large organisation with multiple pools?

Location in relation to possible testing laboratories?

 

 

I don't think you are understanding what I am saying. PAG is not one compound of a specific chemical formulae; it encompasses many, many possible compounds. IR wouldn't to be able to distinguish between these and as such, you cannot correlate the absorbance of any particular peak to concentration in the same manner as defined by Beer-Lambert, meaning you would not be able to accurately or precisely quantify it. So again, IR is a poor choice and would not suit the OP's needs, regardless of how often they need the testing done. 

1 hour ago, studiot said:

 

I agree that's conventional wisdom, but how about this gadget?

 

https://www.bruker.com/applications/environmental/special/analysis-of-aqueous-solutions.html

 

 

It's interesting, but it still doesn't help the fact that IR would not be able to differentiate between the different types of PAG present, which would render any effort at quantification unreliable. Not to mention the undoubtedly huge cost of buying a dedicated machine from a company like Bruker. 

16 hours ago, studiot said:

I said samples because there is no guarantee that distribution would be uniform in a large pool.

I assume that the contaminant arrive from machinery in the inlet or outlet so would suggest paying particular attention there.

 

I suggested IR because the equipment is cheap, widely available and long and well understood.

It also works in a non volatile situation, unlike gas chromatography.

 

I would also suggest that once initial calibration is done it would be easier for continued monitoring/quality control purposes.

 

However it is a long time since I have done any of this so perhaps the analytical chemists amongst us have better ideas.

IR would be a poor choice. As mentioned, the water (a strong IR absorber) would obfuscate the spectra and make quantification very difficult (or impossible), especially if you’re talking about ppm concentrations in swimming pools. I don’t think GCMS is a great choice for a polymer either, as it would be too big and unlikely to run through the column. The other issue is that PAG is not one single compound. You could potentially do it with LC with the right set up and correct detector, but I am not 100% sure on this. This seems to suggest it’s possible, but I didn’t read it thoroughly. 

Where exactly do you need help and can you show what you have done so far?

1 hour ago, Ghideon said:

 

Speculation/Guess: Some kind of indexing job that is running, and (unintentionally) the entries end up in the activity flow?

 

That would be my guess. I had a look at a few of the accounts yesterday and they seem benign. Sometimes we do have spam accounts that registered years ago suddenly make an appearance, updating their profile with photos and spam links, but this does not seem to be the case here. 

Could you be more specific? Sulfanmides appears to be a typo, so can I assume you are talking about sulfonamides? If so, sulfonamides are some of the oldest antibiotics that saw widespread use. They went out of favour because of resistance. Of course, the term is very broad, so is there another type of sulfonamide, or other sulfa drug, that you are referring to? 

40 minutes ago, Ken Fabian said:

 

Brass and woodwind players talk about their instrument playing better after being warmed up by the breath, but it also adds condensation inside the instruments, ie wetting the inside surfaces. Related perhaps?

Koti, Phi for All,  those could be contributing factors but it is such a distinct difference that I doubt they are the main reason -  I don't think my mouth shape is a lot different dry to wet but perhaps tiny changes due to stiffer skin or lip creases may be enough. Would it make much difference in airflow for brass/woodwind players? The seal between lips and mouthpiece should be good and tight either way although for brass the lips touch each other in "blowing raspberries" style and being dry would affect that. Recollecting vaguely my childhood encounters with a soprano cornet, playing with a dry mouth could give me sore lips but I'm not sure I was discerning enough to tell if the sound quality was much affected.

The seal formed for dry vs wet is quite different I think. For brass, another factor is that have your lips lubricated allows you to move your mouth around the mouthpiece easier, which is crucial for several reasons such as creating different sounds / intonations, and hitting higher and lower notes. Couldn’t say if it’s the same for woodwind, but I’ve played brass most of my life.

You are missing so much knowledge required by this question that the only way to really help you here is to give you the answer. That doesn’t help you learn anything, and I personally don’t need to prove that I can complete a first year chemistry assignment. As I said before, the help you need for this is too comprehensive to be reasonably addressed in a forum such as this.  You’re just missing too much of the fundamentals. I recommend this site if you’re interested in studying it some more: https://www.chemguide.co.uk/physical/acideqiamenu.html#top

You’re welcome to come back if you have questions. If not, I wish you the best. 

1 hour ago, monolog said:

When I asked I was told the brackets are there to indicate whatever.

I told you what they represented on the previous page. HA is the general form of an acid (in-tact), and A- is the deprotonated form of the same acid, aka the conjugate base. I was asking you what HA and A- correspond to in your specific question. 

4 hours ago, monolog said:

Not yet, I can't. But I will.

Or maybe I won't. I don't know how to get to those values. I don't even know which is [A^-] and which is [HA]. From the time management point of view it's not fruitful to waste time trying to do some juggling patchwork just to earn another point in this assignment. It's actually ridiculous to waste 2 days on something I could learn in 20 minutes with a private tutor. It's definitely better to move on to geology and make sure I excel in that one as I can actually learn the subject on my own. 

As someone who has tutored this subject for 9 years, I can tell you that you aren’t going to get anything useful out of learning something in 20 minutes if you don’t back it up with your own study. Time and time again, the students I saw who continued to do poorly were always the ones who treated sessions as their primary form of study. 

We are simply trying to figure out what you know and what you don’t, and prompt you in the right direction. If you truly cannot figure out what the acid and conjugate base is in your question, then you are simply not equipped to do this assignment, and you need to (as I mentioned previously) go away and spend time learning and practicing questions related to the module. You are going to spend several hours / days studying this stuff if you want to be able to understand it.

7 minutes ago, monolog said:

So did my false indignation. 

 

I definitely lack basic knowledge. How do I know if a compound partially or fully dissociates into ions in a solution? What in its formulae gives me that information?

There are not a lot of hard and fast rules with figuring it out. There are some things you should know. Organic acids tend to be weak. Carboxylic acids, for example. Ammonia is a good example of a weak base. Strong acids you encounter most are things like HCl, and H2SO4. Strong bases you encounter at this level are frequently hydroxides, like NaOH. Generally though, whether or not you are dealing with a weak acid or base should be implicit in the question. If they give you a Ka or Kb, it’s fair to assume you’re dealing with a weak acid or base. Similarly, if they give a dissociation reaction using equilibrium arrows, it’s probably a weak acid or base. You can also tell by looking at the equivalence points on titration curves, if given. 

25 minutes ago, monolog said:

I wouldn't be here if I knew. Being confronted with my ignorance does not help. Explaining things to me, does.

You should watch some more of those Kahn academy videos. They are quite good, and will help you in your understanding. You will need to spend some more time getting a better understanding of where all these numbers are coming from and how to use the equations and graphs, otherwise you will struggle when it comes to more complex questions. Based on your previous post, you also need to work on the more basic concepts related to stoicheometry, calculating how much product is formed from reactions, limiting reagent questions, etc. Google will provide you a wealth of resources to learn and practice these concepts from. 

19 minutes ago, monolog said:

This is what I did:

"Adding 30ml of NaOH gives us a 130ml solution. therefore:"

Close! You’re mucking up the calculation of concentrations though. In part b., you cannot simply add and subtract the concentration values in the way that you have, particularly since once you add the two volumes together the concentrations change. I would suggest first calculating how many moles you have in the 100 mL of acetic acid and 30 mL of NaOH and rethinking the question with those numbers instead. 

4 minutes ago, monolog said:

He actually uses the HH equation to find the pH.
Honestly, I don't know which species those correspond to in my equation. Would you explain it to me?
Luckily the value for both is 0,769, so I end up with log1 in the HH equation. The pH is 4.74. I hope I got it right.

Where do you get 0.769 from if you don’t know what the values correspond to? Do you know which species the Ka is in reference to? Remember that if we are using HH, we are talking about a weak acid or base. Can you identify a weak acid and/or base in your question? 

44 minutes ago, studiot said:

You haven't given us much detail and Aulton is a difficult book to scan, but this page should supply the other detail, or at least point you in the direction of where to look.

As your graph shows (and is discussed in the text) barbitone solubility is pH dependent.

I would be wary of posting entire pages of text books. I assume it is covered under copyright laws? If so, you may wish to consider removing them from your posts.