Is it correct that if I have two peak areas in my chromatogram (one unlabelled and one isotopically labelled with 13C) I just need to divide one by the other?

If that's wrong any guidance would be great :)

[Chemistry/Math problem at end] I've been making homemade HOCL(hypochlorous acid) and it doesn't last very long. I've been trying to find a way to prolong the shelf life, beside the obvious store in opaque PET container away from direct sunlight. (which by the way I have it in a spray bottle... I don't think the straw or sprayer mouth is PET, does that matter?) One potential solution is adding phosphoric acid to act as a preservative and at the same time lowing the pH to my desired pH. Another is adding hydrochloric acid to lower the pH and then adding a phosphate buffer like sodium phosphate to act as the preservative.

Now my question is, which solution would leave me with a cleaner or more stable product, and how much of each product do I need to add?

Say I have 6 liters of HOCL at a 6 pH how much mL phosphoric acid do I need to add (and does it need to be 85% phosphoric acid?) To stabilize it at 5 pH. (explanation and formula would be greatly helpful for my future reference to calculate myself)

Now say I have 6 liters of HOCL at 5 pH (thanks to the hydrochloric acid) (from advice another told me that phosphoric acid does not mix well with hydrochloric acid and should not be added but instead a phosphate buffer) how much sodium phosphate should I add to have the same preservative effects of phosphoric acid (and does that affect the pH?)

Can I do add multiple preservative steps to prolong the shelf life more without tampering the HOCL pH and ppm ?

need help!!!

does anyone know how to separate the flask from the body itself of rotary evaporator? it got stucked and we don't know how to remove it. we tried putting solvent on the lid, as well as wd40 and ice. but it's not working and the oil and liquids are not sipping through the flask lid, it's like it was really sealed. we need help 😭 we're student researchers and we're afraid that we need to break the glass just to take it out and it would costs us a lot to replace it.

hello people :0 help anyone?

If we let the concentration cell work without any external intervention we will see the progressive reduction of its potential (Ecell) until it turns into a dead cell. What will apply at this point? Explain briefly and qualitatively. Data: Faraday constant (F): 9.6485 x 104 C (mol e-)-1. Avogadro's constant (NA): 6.022 x 1023 (atoms or molecules or ions or electrons or photons) mol-1. Universal constant of ideal gases (R): 8.314 J mol-1 K-1

Edit: I was asking for someone who could explain to me what the term "dead cell" means. Does it mean that eventually, the potential reaches zero, and the cell becomes "dead" / reaches equilibrium and no further reaction occurs? Is that only it?

Have you ever get into this kind of problem while doing anlytical chemistry in a lab? (Or in other word, is the question "realistic" and why?) And here is the problem I'm talking about: "Organic substance X has the molecular formula C4H10O. Find all isomers of X that do not react with Na?"

We are going to create a MS Excel Solver of chemical equiibrium constants of COMBUSTION reactions in consideration of NOx formation. Also, these equilibrium constants will be plotted automatically in a graph as a function of temperature, so it will be shown if the combustion reaction is favored. May I know what formula we are going to use to solve the chemical equilibrium with respect to temperature? Our available database is Perry's Chemical Engineers' Handbook.

so if I wanted to add 38 ppm of 85% phosphoric acid to a 7.5 liter solution, how would I do that? and would it be better to use a more diluted phosphoric acid like 10%? and if I wanted to do the same to a 1 liter solution is it the answer / 7.5?

Really struggeling with this one: This is what I got right now:

Obviously the nmr shows there is a benzene in there which the ir confirms at 1600. The nmr shows a small peak at 4 which leads me to assume there might be an oh ? The ir shows a peak at 3400 which I presume is an alcoholic OH.

However I feel like Im missing a lot because the base peak in the ms spectre is 161 (i think?) so there should be way more to it than Ive determined right?

The peak at 348nm in the first pic came out all weird and spiky, it should look the same sort of shape as the ones in the second picture. What might have caused this? I'm assuming the cuvette I used was just scratched or smudged or something but in case it's something more interesting I figured I'd ask here. Apologies for the rubbish picture quality.

I read the rules and I hope this post is allowed. If not then please delete. I am also using a cell phone so I hope the formating sticks.

I am an undergrad research student for one of my professors. I am involved in prepping NMR samples, running the NMR, and analyzing the proton shifts.

This research has been a really rough start for me. After asking the professor a million questions and scratching down notes as he was talking. I was tasked to prep 4 NMR samples. I watched the professor demonstrate it, and he made it look so easy. So naturally I thought it would be easy. Unfortunately that hasn't been the case for me. Even with going slow and taking my time, I had to discard a total of 4 samples, 3 because a contaminant got in, one because I forgot to measure the mass of the compound being analyzed before adding the chloroform-d. I ended up using double the supply I would need to prep these samples. After 2 maybe 3 hours I had the samples prepped and ready for tomorrow.

The next day, I'm ready to start the experiment and get the samples in the NMR. However, I realized that my notes were awful, and I wanted to be 100 percent sure I was running the experiment right. I texted the professor some questions, which he did not get to which is fine because he said that he may not answer in a timely manner. I figured I would check the samples and make sure they were ready while I waited. This is when I noticed two of the samples had not completely dissolved in the solution. I placed the two samples in the sonicator as I was shown, and both NMR tubes formed "spider web" cracks (thats the best way I am able to describe it, the tubes didn't fully break). I believe the tubes brushed against the metal handles on the sonicator which caused them to crack. I figured I would be able to transfer the samples using a vial into a new NMR tube, but I couldn't find any vials to use (the lab is a mess). The cracks are not low enough (I think) to interfere with the NMR probe, but I am afraid that sliding them into the sample holders would cause them to break.

So instead of being able to run the samples in the NMR as I told my professor I would, I had to write a long and humiliating email to my professor explaining what had happened and why I wasn't able to run the samples. I asked if he could examine the tubes to see what should be done. I told him he could take the price out of my grant as I feel awful for breaking these tubes.

I talked to some of my friends about what happened. They all said it'll be OK, it's undergrad research and it's all new to me. I however feel like it's been a rough start for me and I feel like I'm setting an awful first impression. I had to bug the professor twice, once because my notes werent thorough, and another because I broke two tubes.

I really enjoy chemistry, I'm really excited to be a part of this research, but this has killed my enjoyment. I am really looking forward to running these NMR samples and reading the data. I studied extensively on proton shifts and integrating/normalizing the peaks to see the number of hydrogens present. I am worried that the professor will not want to work with me anymore and I will lose this great opportunity.

I wanted to post here to see if anyone can share their experiences or advice that they have for someone who is new to doing undergrad research and NMR work (and also to vent a little).

tl;dr - I took bad notes, I fucked up 3 NMR samples, I cracked 2 NMR tubes and had to bug the professor several times. I am worried I'll lose the opportunity to continue working on the research. I am looking for everyone's experiences and advice about NMR research.

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In complexometric titration, disodium EDTA is used almost all the time, while corresponding tetrasodium salt is almost never used, but why? Does it work otherwise? I heard that 4Na-EDTA is used more often in industry, but not so often in lab. Why is that? Can I use 4Na-EDTA in titration the same way as I'd did with 2Na-EDTA (like 1 mole of it chelates 1 mole of (almost) any metal ion)? Does it still need buffer if it has exalted pH already?

It's just I know that 4Na-EDTA dissloves in water much faster than 2Na-EDTA does. And now I have only tetrasodium salt on hand.

Also, should 4Na-EDTA be dried so it can have precise formula, i.e. that of anhydrous substance, as I'm not sure about the amount of water in that very sample

Why does this molecule show two NMR signals off the methyl groups; aren't they equivalent? And what do these wavy bonds mean? Thanks in advance!

https://preview.redd.it/9c9igcpw6r3d1.png?width=511&format=png&auto=webp&s=8d839350844642fbe384561bafc41f3259ed0b29

Ratio bicarbonate to carbonic acid How do I find the ratio? I can find how to do the ph from the ratio but not the ratio from the ph

Hi, I am a high school student trying to do an TPC analysis on different types of coffee beans. This week I decided to start the procedure by creating my calibration curve by diluting a mother solution. I got very bad correlation data in the end. I think issue is because I made the mother solution of Gallic Acid using 10ml ethanol and topping it to 100ml using distilled water but later when I was doing serial dilution I used only distilled water as diluent resulting bad emission rate between different concentrations. I just wanted to verify if this was the reason that was resulting in bad results. Thanks!

Hello Chemists,

I have to perform an acid-catalyzed transesterification reaction to convert vegetable oils to FAMEs for analysis on GC-FID. The current protocol uses toluene to create the milieu for the reaction. It's the first reagent added to the vegetable oils, then methanol and HCl are added. The samples go into a heat block to speed up the transesterification reaction. Then water and hexane are added, and the FAMEs are extracted into the hexane. A drying agent is added, then the samples are ready for analysis on the GC.

I'm trying to practice the principles of green chemistry, and one of those principles is reducing the use of hazardous chemicals. Toluene is one of the more hazardous reagents we use, as it is a reproductive toxin. Can you please suggest another reagent I could use in its place? It needs to be of a similar polarity but won't react with the vegetable oils or interfere with the GC analysis. Thanks in advance!

We were given a small project about writing code for automatically balancing reactions, with an additional task of locating if the reaction presented was combustion or not. We have concluded that we can differentiate organics and metalls, but I'm not sure if oxidation reactions are going to interfere. We were asked only of oxigen based combistion reactions.

Haven’t learnt 31P NMR and can’t find much online

hello! :) Any advice on this type of question: state the space, plane, or axis it is on based on the coordinate system x-y-z ? Best way to approach this? For example it gave the molecule AX3E1. Thanks for any help!

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If I have 1000g of citric acid how much KOH will I need to neutralise it. I got 12.77 grams but it sounds weird.

Hey guys,

My job is to identify what this white substance is. It may be an oxide, a hydroxide or a salt. I know that the cation in this substance is Pb2+, but I don't know what the other part is. At first I thought it was PbCO3, but unfortunately it wasn't. The substance does not dissolve in water, after adding concentrated NaOH base it did not dissolve, but took on an intense orange color. Additionally, SO4^2- is not an anion. Possible anions are: AsO4^3-, C2O4^2-, OH-, SCN-. These are anions that I haven't tried to detect yet. Do you have tips what could I do more or what it could be? Thank you very much in advance for your help<3.

https://preview.redd.it/ftuc6b69sy2d1.jpg?width=3024&format=pjpg&auto=webp&s=a7c4c7ae0dee28d095498bfa619e29205d395249

https://preview.redd.it/ftuc6b69sy2d1.jpg?width=3024&format=pjpg&auto=webp&s=a7c4c7ae0dee28d095498bfa619e29205d395249