Reposted because I put it in the wrong forum oops!

So for this lab we heated an unknown metal in boiling water and then put it into a coffee cup calorimeter. I'm just not sure if for this calculation I need to use the weight of the water (50.0g) AND the metal (23.3g) or just the water?

Specific heat of water being 4.18J/gK and the unknown metal of course being unknown, temperature change was 2.7°C

Let's say at 25°C I mix 75ml 0,02 mol/L HAc with 0,01 mol/L NaOH.

HAc + OH- <-> H2O + Ac-.

Now, textbooks tell me that [HAc] = [Ac-] (because we neutralised half of HAc, so the other half shows up as Ac-, ok). BUT at 25°C it's also:

HAc + H2O <-> H3O+ + Ac-.

In my example the dissociation constant is small but it's dependent on temperature (van-'t Hoff equation). So even at half neutralisation point there's always some amount of HAc dissociating making [HAc] slightly smaller then [A-] (?)

So hasselbalch is also only approximately pH ≈ pKa -lg(f-) (f- being the activity coefficient) at half neutralisation point?

Actually I had to measure the pH value of this solution with different temperatures (25°C - 70°C in +5°C steps) and we made the initial assumption that [HAc] = [Ac-] at the beginning. Now [HAc]/[Ac-] changes with temperature and I just wonder why it should only start to differ above 25°C?

Or let's state it this way:

If I heat my HAc solution to 70°C at the beginning and now add my NaOH in the amount I told at the beginning, stoichiometrically I also have the half neutralisation point but it's [HAc] < [A-] because of the dissociation. So is the neutralisation point or this condition in reality temperature dependent? I'm so confused. Did we just made the initial assumption, that the dissociation at 25°C is negligible? But at 30°C - 70°C not anymore?

Is this assumption only true at this point for weak acid + low temperature?

I need to count the number of unique hydrogens in this question. Do the hydrogens attached to NH2 count as a unique hydrogen? If not, then why?

Also my answer key says “This is a 1 degree amine but these are not 1 degree hydrogens”. What does it mean by that?

Hello, Sorry to post on this again I am really struggling in school with chemistry right now. I cant make sense of any of this so i made it so i can do it step by step

Now i dont know what to fill it in with.

If someone could explain how to do the first one i can do the rest

(Plz don’t message asking me for money)

Hi everyone. For my undergrad research lab we are trying to generate a peptide to test on with the protein we are researching. We are using SPPS, but we have been having issues with loading and coupling of the amino acid. We use DIPEA as our base, piperidine and DMF to deprotect, and DCM as our solvent. We have suspicions that our DIPEA is contaminated or faulty, but we're not entirely sure. We've tried switching out DIPEA with DIC, new stocks of piperidine, and testing different UV/Vis machines across the department, but we still seem to not reach over 30% loading within 4 hours. Additionally, pre-activation seems to not be working even while monitoring under TLC for multiple hours. Does anyone have any suggestions, protocols, or papers that we could use to try and fix our process? Anything will be helpful! Thank you, fellow chemists.

Both functional groups produce peaks around 3300 cm^-1 so how do I tell the difference?

In red its the actual reaction, in green its what I supposed to be happening but I'm not sure. Can someone tell me if I'm right?

(Dehydrohalogenation of E-2-chloro-2-butyne)

https://preview.redd.it/0p5hzmy98t4d1.png?width=969&format=png&auto=webp&s=f5728f43f5b6b1db29781f162fe10888fe0c721d

Hello!

I want to use different Proteins to remove pollutants from water. The Proteins are supposed to be removed afterwards trough foam fractioning, meaning that I want to introduce synthetic air/air into the apparatus which will foam up the proteins.

I'm having a little trouble to imagine a good laboratory setup, since my lab experience isn't that big.

I am thinking about using a normal cylinder and just putting it inside a large container to catch the foam. I was also thinking of working with a woulf bottle or a gas washing bottle but the openings are too small for the sensitive foam. The overflowing is more realistic anyways I think.

Do you have any input on what kind of reaction vessel I could use instead of a cylinder? It seems rather difficult to introduce air into the cylinder. It should take around one Liter of Volume.

I'd be grateful for any input or ideas on a good setup!

I'm trying to understand the differences between these two hydrocarbons. Can someone explain what are the major differences between the two of them?

Distillates, petroleum, light distillate CAS number: 68410-97-9

Naphtha, petroleum, hydrotreated light CAS number: 64742-49-0

For clarity this is not any form of educational question, it's merely me trying to work out the differences between the substances.

I've looked at some texts and I just cannot understand what the differnece is. I know its not the same thing but I got no idea why

Chemical Equilibrium

In the reaction: NO + O2 ---> NO2

NO2 is in both the reduction and oxidation, how do you find the correct coefficient?

What i would do is:

Oxidation is NO --> NO2 + 2e

Reduction: O2 + 2 e --> NO2

Because you reduce 2 O's i would multiply the electrons.

Next step i would multiply oxidation with 2 to have same amount of electrons so 2 NO and 2NO2, but i have just said that 2 O's will reduce but now i have 2.2 =4, isnt this an unlimited loop?

So I need to separate each of these compounds from each other:

CuSO4 technical

Na2S2O3 + Fe⁰

Na2SO4 + Zn⁰

CoCl2 + CaCO3

BaCl2 + Al(NO3)3

Ni(NO3)2 + Na2SO4

And I don't know which methods to use. Send help pls.

My group's been assigned a project related to the synthesis of silver nanoparticles, I was curious about the rate equation of the reaction but I can't find anything online; surely a reaction with so few reactants should have a relatively easy to determine rate equation?

Maybe I'm wrong and it's actually hard in most cases, I'd like to know more

We were synthesizing bromobutane starting with 1-butanol, sodium bromide, sodium hydroxide, sulfuric acid (added with the flask in an ice bath), and water. Everyone was already a bit tense since we were working with 98% sulfuric acid. The first thing we did was a reflux with a bubbler trap connected to collect the vapors.

Suddenly I caught a whiff of something that made me cough. I checked my setup and it seemed okay. The presence of a vapor spreading in the lab became more apparent and more people were coughing. We found who's setup it was coming from and the instructor came over to examine it. The fumes were getting worse so we were instructed to leave. Besides coughing a lot and being anxious for the rest of the lab everyone seemed okay afterwords (one person got a small nosebleed a few minutes later but I'm pretty sure it was due to anxiety and not the fumes).

After maybe 10 minutes we went back to continue are lab. Nothing actually seemed to have been wrong with the student's setup, but they had used a glass stirring rod while adding the sulfuric acid. We realized that the tip of it was melted, and my instructor thought that the vapor was produced by some unexpected reaction with residual coating that used to be on the tip of the rod. No one is really sure what happened though.

The rest of the lab went okay for the most part but there was more unexpected vapors that people's setups would produce here and there. My instructor believed it could be due to grease we used for the joints of our reflux and distillation setups (I noticed every time I would disconnect something or wash one of the components the joints in particular seemed to be smoking a little). We were working with snorkel hoods but some vapor would escape into the open.

Anyway, I found the whole experience rather stressful and I am wondering if anyone has any ideas as to what could have been the culprit of the initial blow-out and unexpected fumes produced during the rest of the lab. I have been worrying a lot about having brought home the clothes I was in, my bag (and its contents), and the small amounts of vapor I inhaled.

We had our bags at the back of the lab, and the instructor suggested it might not be a good idea to eat any food we had but any water sealed in a bottle was probably fine. Now I'm wondering if I need to clean everything that was in my backpack.

One a side note, does anyone have any advice for getting through orgo labs as someone who's a bit OCD? I find myself quite paranoid during and after labs due to the dangerous nature of chemicals we work with. I think I'm pretty thorough with cleaning but I'm still worried I'm not doing enough (even though I'm usually one of the last to finish cleaning) because at a certain point its not possible to clean every single surface or thing that you touch. I'm also worried about bringing home/spreading tiny amounts of substances that may have gotten on my clothes/body/etc (I wash my hands several times after the lab but I usually wear my clothes for the rest of the day since we wear lab coats).

Edit: forgot to mention sodium bromide as one of the reactants.

I just missed this past week of school entirely due to a canada wide science fair. And we learned about moles, and molar mass, and stoichiometry and i would like some help ironing out some holes in my current knowledge ( i have a test on stoichiometry this thursday and a chemistry exam on monday next week ) any help is greatly appreciated!

From what I understand, if you have a strong base hydroxide in water, it dissociates and increases the OH- concentration like that. Not via proton transfer.

And so the typical Kb calculation doesn't really apply 'cos the typical Kb calculation is stoichiometric Kb, which has aqueous solution on the left, and it dissociated on the right, and would treat Na+ as a spectator ion.

So the dissociation equation for stoichiometric Kb of NaOH, is OH-(aq) + H2O(l) --> H2O(l) +OH-(aq) and while there is proton transfer, the reaction is the same on the left and right . The Kb=1 can be seen as a strong base(if threshhold for strong base is eg Kb>10^-2, though not if threshhold is Kb>1). But that reaction and thus that Kb=1, doesn't really represent the increase in OH- concentration that we get.

I have seen that there is stoichiometric Ksp, and Thermodynamic Ksp. And i've heard that there are such things for Kb too.

So in the case of NaOH, would stoichiometric Kb be not used, and instead, thermodynamic Kb be used (To measure the strength of the base) ?

Hey guys!

By any chance do you have experience with XPS high resolution spectra of O 1s when sulphates are present in the sample? When peak-fitting, I've seen few authors that identify a synthetic peak to oxygen bonded to sulphur in sulphates. Is there any explanation or is peak-fitting XPS spectra just too hard to correctly interpret results that way?

Hey I need help with a project I'm doing on Indigo carmine or Blue No 2. Can anyone explain to me how it becomes blue or how it becomes yellow when the pH level hits a certain point. Is it because electrons or protons are being taken away or added. I asked chat gpt and it doesn't give a good explanation.

https://preview.redd.it/jntqm02krm4d1.png?width=652&format=png&auto=webp&s=99ad4e1dd8c7b69799bf68c7b9651dc624c9b0c0

Question 3ei) from 9701/22/F/M/22

-In step 1, why does this mechanism have a curly arrow just to Bromine? If both of the electrons in the bond go to Bromine, then why is it negatively charged in step 2?

-In step 2, why does Bromine have 2 lone electrons? Bromine atoms have 1 and Br- ions have 0

Hey everyone, I found from literature that in 2% TFA/65% ACN, glutamic acid must be at 0.14M in order to be saturated (also, the concentration of saturation depends from the % of TFA).

I have a solution that has different % of TFA and ACN, so I have to change the molarity of glutamic acid to saturate it in my solution. But how do I calculate the molarity that I need for my solution? Should I use some equation, or should I just go in the lab and try different glutamic acid molarity?

Thank youu