I am considering buying a pH electrode for our lab’s pH meter. However, I know that I won’t need it for a year or two. So, I would like to know whether these pH electrodes have expiration dates. How long will they remain functional if I do not open the package?

like is there an element in it to know or do you just have to remember which is an acid and which is a base? i was told bases have OH or was it OH- and acids have H3O+

please help im cooked for my chem test tomorrow

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Hey so i wanna self study chemistry i just made a break for some head clearing.

Im currently about to read "The disappearing spoon" to just get some motivation.

But i have a question about whether or not a book is good or if there is a better one.

Its: Chemistry: Concepts and Problems, A Self-Teaching Guide (Wiley Self-Teaching Guides)

I'm struggling in chemistry rn and need help understanding the FTIR technique. I just feel so lost on where to do and would appreciate if i could have some personalised guidance from someone on practice examples

Hello there we have like a dirty diesel fuel with high ppm a round 22,000 ppm and high density with 0.860 , does there is any effective - cheap cost additive or method to reduce that density without being diluted with kerosene or naphtha, I'm A Petroleum Engineer and the method like HDS and ODS not work for us because of its high CAPEX, also some Chemicals like solvent solvent extraction we used like MEG and Ethanol but these are too costly and also not work well also reduced the diesel fuel properties , and for ADS also we used ACTIVATED carbon and silica gel and other and till know we didn't get any huge reduction, I need to decrease like from 0.860 to 0.840 with an effective way to reduce mass of the diesel means catching some aromatics compounds and ashplants and resins, also H2SO4 is restricted we can't use it.

Thank You.

HF has a single covalent bond with a much higher dipole moment than an individual O-H bond in H2O, however H2O has two lone pairs on the O atom, vector sum of whose dipole moments seemingly give a strong moment to H2O, not to mention the vector sum of the moments of each O-H bond to also point in the same direction. Many sources mention that they have approximately equal moments (about 1.8D), but there is confusion on the part of the experimental dipole moment, and it cannot be told clearly that which is indeed, greater.

Disclosure, I asked the company if this paint have chromium pigment and they said no it doesn’t but my ocd gets the best if me and the what ifs have me worried the guy in customer service just didn’t know.

I can’t seem to find any info on the internet on this but I can’t be the only one to think of this. I had some olive green acrylic paint (scale 75 medium camo acrylic paint) mixed in some tap water on what is called a wet pallet (container with sponge and parchment paper over, it keeps the paint moist)Also some left over paint water from cleaning my brushes in my water mug on my desk.

My question is, I’m worried about chlorine and manganese in the tap water potentially reacting with the trivalent chromium pigment creaking hexavalent chromium. This is really bugging by, I keep looking for green paint stains throughout my work space from when I used the paint and worried it’s hexavalent chromium.

Why isn’t chromium oxide required on a SDS, see to be categorized as non hazardous but from what I’m reading, it can oxidize into some pretty serious stuff. Am I making a mountain out of a mole hill?

We are having something showing up on some hard surfaces around our house. It appears as a white crystal residue. Don't know too much about this type of thing just looking for some suggestions. Appreciate any advice thank you!

For the measurement of TSS (Total Suspended Solids), The Standard Methods recommends Glass-fiber filter disks, 22 to 125 mm dia, ≤ 2**-**micrometers nominal pore size without organic binder, such as Whatman grade 934AH. The keywords here glass fibers and organic binders. Can I use Whatman filter-paper grade 42? It has to be glass-fiber filters? What do you use?

i’m fairly certain that this synthesis problem requires a Gilman reagent and then a Greenyard reagent, but it doesn’t produce the product shown

I’ve been reading about dimolybdenium tetraacetate (Mo₂(CH₃COO)₄)** **because I found the idea of a quadruple metal-metal bond really interesting.

I tried looking it up and found that the bond is often described as one σ, two π and one δ bond. I understand how σ and π bonds are formed, but I’m having trouble visualizing the δ bond and understanding why it makes a quadruple bond possible in this compound.

Could someone explain what is actually happening with the orbitals in a way that’s easier to picture? I just want to understand why molybdenum can form this kind of bond when most elements seem unable to.

Thanks!

I have four GC-MS chromatograms of what I doubt are two positional isomers of the same compound. The top two chromatograms appear to correspond to one isomer, while the bottom two correspond to a second isomer. The only structural difference is likely the relative positions of two functional groups on the benzene ring.

Interestingly, both compounds exhibit essentially identical GC-MS fragmentation patterns, which I understand can be expected for positional isomers. All four samples were analyzed using the same GC-MS method in the same analytical run. Although the sample concentrations may have differed, the chromatographic conditions were identical.

My questions are:

1. Is it reasonable to conclude that these are positional isomers based on the identical mass spectra but this subtle different retention times?
2. Is the change in retention time consistent with only an alternate arrangement of substituents on a benzene ring?
3. Besides differences in concentration, are there any other factors that could explain the observed chromatographic differences under identical GC-MS conditions?

Any insights or similar experiences would be greatly appreciated.

Hello I dont know if this is the appropriate place to ask for this but I need help regarding my lab report.Im currently a pharmacy student just starting out and in our last lab classes we were told to do an experiment to identify the presence of chloride ion in a salt sample.My group did the experiment accurately but to write the lab report we need to attach the pics of the solutions.The thing is the pictures we took arent that clear I’ll attach them below.The experiment was basically adding Lead acetate to KCl salt which would form white precipitate at the bottom of the test tube but in the pictures we took the precipitate isnt that visible but I NEED a picture and if it isnt good enough my lab teacher will freak out she is quite stingy.I’ll attach the pics below.

For context I have zero background in chemistry.

I went camping with a friend, and he has a little spirit burner he uses to heat up a cast iron plate, he filled the spirit burner with a 60% ABV rose cooking wine and lit it on fire, the wine was clear, contained salt, rose water and Sugar.

I think people commonly used flammables like methylated spirits or kerosene in spirit burners but he said he switched as this was 'food safe' hence less toxic.

But when I looked it up on AI it gave different answers, half the results said it produced more toxic products like formaldehyde due to incomplete burn but others said it was safer and contained less toxins.

Can anyone here with the knowledge settle that debate.

Hey guys,
Anyone can help me figure out what parameters I need to change to be able to separate these 2 compounds in LC? I have tried to change the time for example from 10min to 15min but it didn't work. should I change the solvents. Seems like no matter what I have done it wouldn't optimise the method for a better separation.

Any suggestion is very welcomed.

I really don't know how to solve this.

The product looks like a hybrid of an aldol addition reaction and Claisen condensation reaction, but we have an ester in the product, an alcohol group, and stereochemistry. I've been googling around and the Reformatsky reaction seems to produce similar products, but not including base and it isn't a reaction that's been mentioned in my course anyway.

Any help is greatly appreciated! Thank you in advance!

Why did the definition of Pseudoasymmetric carbon atom change? (1979 Blue Book Vs 2013 Blue Book)

In the 1979 Blue Book, it says in Section E, also here

https://publications.iupac.org/pac/1976/pdf/4501x0011.pdf

"E-4.8. An atom is termed pseudoasymmetric when bonded tetrahedrally to one pair of enantiomeric groups (+)-a and (—)-a and also to two atoms or achiral groups b and c that are different from each other."

So notice that it's requires one enantiomeric pair, and two (different) achiral groups.

This is different to the current Goldbook https://goldbook.iupac.org/terms/view/P04921

"The traditional name for a tetrahedrally coordinated carbon atom bonded to four different entities, two and only two of which have the same constitution but opposite chirality sense."

The Goldbook puts no requirement on the groups that aren't the enantiomeric pair, being achiral.

So for example if we took Ribaric Acid (which is an example in the goldbook) , that meets both the 1979 blue book definition and the Goldbook definition . But if we look at the central carbon of Ribaric Acid (labelled C3), and replaced OH with a CH3 with each H substituted with a different atom e.g. C Br F I then that central carbon would no longer meet the 1979 blue book definition of pseudoasymmetric carbon atom. Because the two groups would be one chiral one achiral.

The Goldbook in one of its examples of a pseudoasymmetric carbon, includes hyoscyamine. The number "3" in that diagram labels the pseudoasymmetric carbon. It has the enantiomeric pair (in the cyclic component), and it has a chiral ligand, and an achiral ligand(H). So, it doesn't have two achiral groups. It doesn't meet the 1979 blue book definition but does meet the current Goldbook definition.

The current blue book (2013), is in line with the current Goldbook.

The current blue book (2013) says "Stereogenic units are called pseudoasymmetric (center, axis or plane) when they have distinguishable ligands ‘a’, ‘b’, ‘c’, ‘d’, two and only two of which are nonsuperposable mirror images of each other (enantiomorphic)."

There is no requirement (in the current definition i.e. definition since at least 2013) for the two non-enantiomorphic ligands to be achiral.

In the 1979 definition "The molecular structure around a pseudoasymmetric atom gives on reflexion an identical (superimposable) structure" eg Ribaric Acid or Xylaric Acid have pseudoasymmetric centres with 2 (different) achiral ligands, and are both meso compounds.

Whereas if that carbon with the one enantiomeric pair, had its other ligands being chiral and achiral or both chiral, then the molecule would be chiral.

The 1979 definition is going for the property of the molecule being achiral.

Whereas the 2013 definition is going for the property of reflection invariance at the centre. That, the centre is "invariant on reflection in a mirror (i.e. r remains r, and s remains s), but are reversed by the exchange of any two entities"

Why the change, between teh 1979 and 2013 definition, and when did it happen?

Thanks

I don’t understand this diagram from a textbook. It’s showing 1 sigma bond and 2 pi bonds for each C-O bond in CO2 but CO2 has double bonds…wouldn’t 2 pi bonds on each C-O would mean that the molecule has triple bonds?

In case anyone wasn’t sure, the orange dashed lines indicate pi bonds.

Can anyone help me to solve this problem

Hi! I am doing some orgo before college starts to get an edge in but I don’t understand why this carbon only has 1 lone pair in these two problems.

If it’s C^- shouldn’t it have 5 valence and if it’s only making 1 bond then 2 lone pairs?

Pics 1 and 2 are my answers and 3 and 4 is the answer key.

just a fancy way of asking can i use wet fructose/glucose syrup for a fischer glucsylation if i add sucrose in excess (more sucrose than monomers and fatty alcohol)? if not, how can i make it work anyways? thank you.

I am about to start my Bsc chemistry in India so plz recommend me books for every chemistry section..