/r/chemistry

Photograph via snooOG

A community for chemists and those who love chemistry

Rules: Violating a rule will result in a ban.

  • Ask homework, exam, lab, and other undergraduate-level questions at ChemicalForums otherwise it will be deleted.

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  • Likewise, simple pictures of uninteresting and garden variety chemistry-related things are not appreciated. If a caption or explanation is included this helps, but please use your discretion.

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Notes:

  • If you're looking for a more concentrated, advanced discussion of chemistry topics among professionals and grad students, check out /r/Chempros.

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Past Weekly Topics

/r/chemistry

2,524,265 Subscribers

1

VOLUMETRÍA O TITULACIÓN ÁCIDO-BASE 2: ACIDIMETRÍA

Este video es la continuación de la anterior, en este te enseño a determinar la concentración de un ácido por neutralización con una base patrón (de concentración conocida). Es muy importante estos tipos de análisis ya que se utilizan en control de calidad. Por favor, darle like y suscríbete a mi canal, ahí podrás encontrar más vídeos de otros temas. Gracias.

0 Comments
2024/03/28
06:30 UTC

0

TITULACIÓN ÁCIDO BASE 1: ALCALIMETRÍA

En este video te enseño a determinar la concentración de una base o hidróxido por neutralización con un ácido patrón (de concentración conocida) de manera teórica y experimental. Gracias por verlo.

0 Comments
2024/03/28
06:23 UTC

2

HPLC UV/Gamma

Hello ! after the synthesis of my 89Zr-Deferoxamine-Antibody i had to do an HPLC to determine potential impurities in my solution before injecting it into my murine model. Can you guys confirm that the first pic is the « 89Zr-Deferoxamine-Antibody » and the second is « 89Zr-Deferoxamine » even though i think it might be free 89Zr in my PBS solvent.

4 Comments
2024/03/28
05:48 UTC

1

ELI5: If ∆ G = ∆ H - T ∆ S, then why does increasing temperature for an exothermic reaction make it less favorable?

2 Comments
2024/03/28
04:55 UTC

2

What's you favorite molecule?

Mine is tetraxenonogold(II) undecafluorodiantimonate. It's super interesting and completely useless... other than the interestingness of is existence.

AuXe4(Sb2F11)2

1 Comment
2024/03/28
02:50 UTC

1

Best coating for homegrown crystals?

I started making some copper sulfate crystals and I plan to start making some chrome alum ones soon. Initially it was just an experiment to entertain my little siblings, but it has now turned into growing the purest crystals I possibly can. My immediate thought was clear nail polish or some kind of diluted epoxy as a coating. I decided I’d hop in here to ask before purchasing anything in case there are obvious pros/cons, or hidden gems, that I’m not aware of. Thanks!

1 Comment
2024/03/28
02:45 UTC

43

pH indicator during the electrolysis of table salt

So I guess electric field visualized or smth

13 Comments
2024/03/28
01:43 UTC

0

do i stand a chance at CU Boulder's PhD program with a 3.1 gpa?

would love to hear from any grad students currently going here.

my gpa is pretty low, but i was an REU intern my junior year, and got a lot of research experience in an analytical/electrochem group throughout my undergrad. i have good relationships and letters of rec from my professors also... i also have a small bit of industry experience working as an analyst for an environmental based company.

i've spent a lot of time in boulder, and have friends there and know the area very well. i was considering trying to reach out to analytical professors ahead of time to maybe introduce myself?

5 Comments
2024/03/28
01:24 UTC

2

If I add 10g of salt into 100ml of Water

stir it and let it settle for a day (container sealed no evaporation) will the salinity in the bottom be a little bit higher as in the top because of gravity?

6 Comments
2024/03/28
00:23 UTC

1

How do I get rid of Cu(II)Cl2 waste?

1 Comment
2024/03/28
00:19 UTC

1

Hydrogen Peroxide

Don’t really know where else to get this answered so hoping you guys can help. Can anybody explain why I can’t buy hydrogen peroxide anymore? I used to be able to buy 3% food grade from any chemist. It’s unavailable everywhere now, I don’t trust Amazon sources but why has it stopped being sold?

4 Comments
2024/03/28
00:08 UTC

0

Which One Has The Most Lithium?

Making A Periodic Table Collection and Need help with which one has the most lithium.

9 Comments
2024/03/27
23:55 UTC

1

ICP-MS reputation

Was all set to pull trigger on getting a Shimadzu ICPMS-2050 and someone told us to go with Agilent. Now frozen and seeking advice (for Pb, As, Cd, and Hg in cannabis vape concentrates (respective max limits: 0.5, 0.02, 0.02, and 0.1 ppm). Thanks.

2 Comments
2024/03/27
23:52 UTC

0

Hexamethyldisiloxane "reactivation"?

Hello. Forgive me as I am no chemist and so the terminology is not quite there.

I have a product named Derma-tac which ingredients lists only Hexamethyldisiloxane. Its intended purpose is a skin to silicone adhesive. As the bottle I have has exceeded the labelled shelf life, it has turned from a viscous fluid to more of a solid gel-like substance. My question is is it possible to "reactivate" the material somehow so that it may be used again? Or have I just wasted money by leaving it in a drawer for too long?

Here is the product page: https://www.smooth-on.com/products/derma-tac/

I have also sent a message to the manufacturer and am awaiting their response, but I also figured it wouldn't hurt to ask someone not from the company that might well just encourage people to spend more money with them.

Many thanks.

1 Comment
2024/03/27
23:26 UTC

12

I'm a chemist and I'd like to introduce myself to coding, I don't have any background. Is there any specific area to start with?

8 Comments
2024/03/27
22:54 UTC

2

How do I break bad news to my PI?

Hello all, I am a first-year PhD (23F) student at an American University. As I am coming to finishing up my first year I realized this decision of mine might not be what I wanted (PhD). I am interested in mastering out as of recently for a variety of valid personal reasons. I joined a research group this year and am curious as to when and how should I tell my PI that this is my plan now. Please and Thanks

5 Comments
2024/03/27
22:42 UTC

21

Ammonium sulfamate tar

My sulfamic acid was blue for some reason and I didnt bother to recrystallize it before making the ammonium salt of it. I got this instead

5 Comments
2024/03/27
21:09 UTC

1

Intro to Gen Chem Curriculum

Hi all,

I’m new to this sub, but was hoping to pick your brains about a project I’m working on.

I’m trying to design a general chem 1&2 (intro or first college chem class) curriculum for a humanities class project, where I’m trying to incorporate real case studies to illustrate examples of why chemistry is important beyond the classroom. The goal of this public facing project is to educate students and future physicians and scientists on what they can accomplish beyond the classroom. An example would be: why knowledge of simple acid base chemistry and solutions could’ve impacted the Flint water crisis.

I’m looking for more case studies and examples which I can use to introduce a general chem concept and incorporate why this is important for us as future leaders, policy makers, and how it impacts low income and marginalized communities.

I apologize if this is not appropriate for this thread, but would appreciate being pointed to the right resources, or any niche examples you may know!

Thank you!

2 Comments
2024/03/27
20:54 UTC

7

So according to Lewis, is NH4+ an acid or a base?

So it is formed by this reaction NH3 + H+ >>>>> NH4+

We know that the proton is an acid since it essentially receives a pair of electrons from N.

And with that we conclude that NH3 is a base since it gave a pair of electrons to the proton allowing the creation of a Harmonic Bond.

With that said, is the result an acid or a base? Since it is formed using an acid-base reaction does that make it both?

11 Comments
2024/03/27
20:42 UTC

2

Thermometer repair?

8 Comments
2024/03/27
20:19 UTC

3

Can someone explain why cherry-flavored carbonated water fizzes more and goes flat faster than other flavors?

Question in the title. This has just been my experience. I think maybe the "natural flavoring" is somehow helping the carbonation out of the water, but I'd like to know more details if anyone can help.

3 Comments
2024/03/27
20:00 UTC

2

Is Brilliant.org worth it as a Chemstudent?

Hey there i was wondering if anyone of you has tried Brilliant.org it has sponsored multiple Youtubers i personaly like to watch. I also tried it and it seems to be quite great though i dont have the premium and without premium it seems quite useless as its only the introductions of courses. Im thinking of buying the Premium version though im not sure its worth it for me as a Chemistry student as there seems to be only one Chemistry related chapter in the Science course. Has any one of you guys tried it and can say wether Brilliant.org has helped your understanding pf chemistry/ mathematics and physics related to chemistry?

4 Comments
2024/03/27
19:09 UTC

23

How important is GPA for chemistry jobs?

I have been applying to entry level jobs and was wondering if it's normal for jobs to ask for your transcript? I am a capable worker and have always worked well individually and in a team in my past job and labs. However, because of circumstances my culmulative GPA is a 2.3 with my major GPA being a 2.5. If you combine all my coursework my GPA is above a 3.0 but I attended multiple colleges so its all calculated separately.

I have a valid explanation as to why my grades were so poor, and outside of the few classes that messed up my GPA I did decently well.

I have an interview coming up for a very basic entry level position and the recruiter asked for my transcripts. I left a brief explanation but it's freaking me out and makes me wonder if I won't be hired anywhere in the Chem industry. Advice would really be appreciated!

44 Comments
2024/03/27
18:21 UTC

0

Have any of you got red eyes after each lab?

So i am taking 4 labs this semester , organic , industrial , general and analytical , i already have sensitive eyes especially in spring , but i never had red and burning eyes for no reason , so i suspect it is from the chem labs...?

8 Comments
2024/03/27
18:16 UTC

2

Doped nickel foam Under SEM

I was wondering if anyone could tell me if they have any experience with running nickel foam under an SEM.

Sadly The SEM at our university has broken down (again) and so i have to send samples of my product away for characterization. However when i normally prepare my nickel foam for electrolysis i normally coat the foam by adding it into a suspension of my catalyst and sonicate it, i will then take it out, wash off excess material and dry it.

Once i run it i do get results, but the coloration of my nickel foam remains a shiny silver/grey color as opposed to the dark black solution its suspended in. I'm afraid that if i send it for SEM there may not been much material adhered to the Nickel foam.

Any help is greatly appreciated.

0 Comments
2024/03/27
17:52 UTC

1

Remove water from viscous ester

I have an ester on (glycerol + acid) that has a high viscosity (50 Pa s). reaction to make ester (stirred for 4 hours with mechanical stirrer)

How would I remove water?

6 Comments
2024/03/27
17:20 UTC

636

I hate organic chem

I was supposed to "dry" the methyl benzoate...well..🙂

98 Comments
2024/03/27
17:11 UTC

0

Blue Chromate - what am I getting myself in to?

Hello all. I'm exploring doing some metal refinishing at home. Blue Chromate was recommended to me. Here is the SDS:

https://caswellplating.com/content/sds/Blue%20Chromate.pdf

The SDS says this contains chromium(3) which I have been told is different and safer than hexavalent chromium. From what I know of hexavalent chromium it's pretty nasty, so "safer" than that isn't super reassuring.

The SDS also says this contains ammonium bifluoride, which from a cursory glance through this site seems particularly nasty.

I have some minimal PPE (gloves, a respirator I use for painting, etc.) and a well-ventilated garage. But I don't know enough about this stuff to know if I'm ok or in way over my head. Would this be something you'd consider using at home?

EDIT:
Info from the SDS:

  1. WATER Concentration 74.5 - 80 %

  2. Nitric acid, chromium(3+) salt (3:1) Concentration 14 - 17 %

  3. Nitric acid (<40%) Concentration 10 - 12 %

  4. Sulfuric acid (<10%) Concentration 1 - 2 %

  5. Ammonium bifluoride Concentration 0.5 - 1.5 %

1 Comment
2024/03/27
16:55 UTC

0

GC-MS results

I am being required to identify a compound using GC-MS for school and I have no idea what I'm doing as it is my first time doing something like this. I have the peak retention time, peak start and peak end, peak height and peak area, concentration and theoretical plates. Is there any way to identify a compound from these alone, and how would I do this - if not what information can I actually get? I have used an internal standard and my unknown, but I did not have time to obtain enough information for a calibration curve.

1 Comment
2024/03/27
16:51 UTC

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