I have an exam coming up and safe to say I did very badly on the practice quiz. A more full list of what I need to know looks like this (aka what I’m getting lost on)
-when are double bonds possible

-recognize when resonance structures are possible, and draw all

possible resonance forms

-calculate formal charges for atoms and include these on structure

-calculate formal charge

select the greatest resonance contributor

• use VSEPR and the Lewis structure to

-correctly identify shape and bond angles

-sketch geometry using a simple line-drawing

-predict the overall polarity of a molecule (using both ΔEN and geometry)

-predict the hybridization of a specified atom in a structure
-determine the number of σ and π bonds in a given molecule

-explain/describe the formation of double and triple bonds in terms of σ and π

bonding

-describe the bonding in a simple covalent species in terms of the bonds and

hybrid orbitals involved
I know It’s a lot but my textbook is not very good and my professor mainly puts photos on her slides, I’m super lost and don’t even know where to start.

How do you know what the limiting reactant is without the pic?

I’m very confused with this. I’ve been good and understand the chemical balancing of a normal equation. But now I’m trying ionic ones and getting confused. In order to complete these do I need to know the charges of some transition metals? Like lead, copper ect? Is that how this was done.

Not sure if my question makes sense or not. But is this also an oxidation question? Or is ionic equation different than oxidation reactions

I have a solution I’m running an NMR on. My solvent is DMSO-d6 but my compound has a few amines. To ensure my peaks are correct, I added a few drops of D2O to check them. However, in doing so, I found that a triplet, one I did not associate with the product, also disappeared. I thought the only peaks that would disappear were singlets (i.e. exchangeable protons like -SH, -OH, and -NH2). Can anyone help explain what is going on?

I am doing an experiment with STM and have to use Gwyddion to determine the grain distribution. As it is my first time using it, I am not entirely sure how the mask is supposed to look like and google is not being particularly helpful.

I used the water shed feature as recommended by the assistant. The experiment had us look at gold sheets.

The 1st picture is without the mask and the second one is with it. I think that the lines are correctly placed, but the graph that came out for it was rather jagged.

Thank you in advance for your help.

I came up with 1,4 bi-isobutylene-heptane (a) and 1-isobutyl-pentene (b). Am I close? What might I be doing wrong? Thank you.

I got an exam tomorrow for pchem and for the life of me, I cannot get these two topics. (I feel really good about the rest of the topics) I know a (degree of disassociation) is like the percentage of how much is taken away(?), but I feel very iffy on that. maybe I'm slow but I don't understand IE tables. does anyone have links to videos? i don't think the organic chemistry tutor made videos on physical chemistry and I cannot find any videos on pchem. lol thank you!

Hi yall, im in college right now—my second year—and I’m doing so horribly in chem. I want to be premed but my grades are abysmal (like C+ B- range and I know I need to be at least a B+, ideally A). The first year I was only sort of locked in and I did all my assignments and homework but I didn’t really go to office hours that much. On those exams I always did pretty poorly even though I felt like I mostly understood everything. This year I wanted to turn it around. I arranged tutorings twice a week, I went to office hours, and I studied for hours each day. I basically had to relearn a lot of basic fundamentals but now I’ve gotten to the point where I can actually follow along in class and understand what my professor is saying. I felt so proud of myself for reaching this point—for catching up to the point I didn’t feel like I lagged behind so much. Anyways, I checked my first exam grade the other day and it was actually trash. Like 50%, I failed that exam no questions asked. I feel so bummed too. I knew there’s no way I got everything right but i felt like I understood most of everything and it just sucks to see that after I spent so long studying and building confidence. I feel horrible too because I was trying to build rapport with my professor and joke a bit with him in between office hours (like saying I really liked his pets that he showed to the class and I shared his music tastes). Now I just feel embarrassed because I was so confident and my test score had nothing to show for it. I want to talk to my professor and get advice but I’m worried I won’t be able to control my emotions and leave our conversation in an awkward spot.

I think the worst thing is, I’d always functioned on the mindset that hard work leads to good results and if I work hard, I’ll do well. If I’m doing so poorly, does that mean I need to work harder? Maybe I’m not studying right, but I feel like through my studying I’ve genuinely developed a more complete understanding of mechanisms and reactions and why things happen rather than that they simply do. It’s gotten me to the point where if I’m stuck, at least I know basic starting points to work off from (like how an acid will more often than not, protonate. So if I have an acid and an OH in my starting material, there’s probably going to be pronation happening). My next exam is coming up soon and I’m so nervous and anxious that I’ll do poorly again and won’t be able to have my upward trend I was aiming for premed.

I have a solid mixture of two substances, one of them having a pH of 4.2 when at a concentration of 5 percent in a solution and one of them having a pH of 5.3 under the same circumstances; how would I go about isolating them? I know that I have to pulverise the solid and form a solution with it, and I know that somehwere along the road I'll probably have to use dichloromethane or chloroform, but that's literally all I know. Can anyone help?

Hello Gen chem 1 here. I’m trying to figure out balancing chemical equations doing okay so far. But now confused on what the heck these parenthesis mean.

See that’s the thing with chem man there’s always a bunch of tricks and more steps. Once you think you have it figured out this type of stuff starts popping up😂

First of all yeah my chem background is bad but now I just have to take this course and I’m GENUINELY trying to understand.
So my question is, can anyone please just simplify the rules of how to know what angle the bond has and what hybridization??? Those ochem just piss me tf off I try to look for an explanation they either be beating around the bush or explain really really simple examples and avoids doing the tough ones.
This is one of the questions I got stuck on, it asks for the angle and the what kind of hybridization it is. I basically said it’s 120 degrees (randomally) and I guess it’s a sp^3 hybridization???? Idk I’m so pissed rn and I’m sorry again if I don’t make sense I’m telling u guys I don’t know shit but I’m trying I swear

This is one of my exam questions, yes there was an extra h2o but idk where it comes from

My textbook said that Solvolysis is only an Sn1 reaction, but other sources say it can be other mechanisms lol, what is true?

And if it is only an Sn1 reaction, does that mean solvolysis will not form any sort of alkene product made by an E1 mechanism? Like zero e1 product whatsoever, not even as a minor product?

Also: after an OH in a substrate is made into a good leaving group via turning grabbing an H and turning into an H2O+ molecule,

how do you know when the newly made good leaving group will break off on it’s own vs. when it needs to be forced out via an Sn2 or E2 mechanism

Why do you have to specify that the methyl is in position 1 of the ethyl? If it was on carbon 2, it would just form a propyl, so a methyl can only be in carbon 1 for it to be a isopropyl.

i think that the double bond inside ring will not be reduced as it will be hindered by the big structure of 9-BBN and just wanted to confirm if i thought the right mechanism

I understand that the first molecule with the bromine has a plane of symmetry because both bromine’s are wedged. However, I can’t figure out why the second molecule has a plane of symmetry? The hydroxides are opposite, one dashed one wedged. How are both compounds meso though? I get that to be meso u need 2 chiral centers with each stereocenter being attached to the identical groups . The second molecule shows this, but the orientation in space makes me think there isnt a plane of symmetry internally. Idk if this makes any sense

Hello, in my ap chem class we’re learning solution stoich and problems involving molarity and volume etc. and i am just so lost. anyone have resources? thank you!

In my answer, I said that "a" and "b" are the two highest priorities. Because they are on opposite sides, I chose "E" configuration. My answer key says that "a" & "c" are the highest priorities, making the configuration Z. What am I missing?

Chlorine is obviously the highest priority, but isn't "b" > "c" because the first point of difference bonds to another carbon?

Based on the experimental setup, Beamer B acts as a control that continuously produces Oxygen gas, creating a baseline pressure that pushes the disc to the left. When the disc moves left in Trials 2 and 4, it indicates that Beaker A produced less gas than the control, meaning Beaker A is effectively being compressed and work is done *on* the system (making work positive, not negative). Conversely, when the disc moves right in Trial 3, Beaker A produced more gas and expanded, meaning it did work on the surroundings (making work negative, not positive). Last thing in Trial 1, the disc does not move, indicating balanced pressures with no significant net expansion or compression, which contradicts the statement that work is done on both the system and surroundings. Because every specific claim about the trials violates the standard sign conventions for thermodynamic work and gas production so this is why none of theseis the only accurate choice

here’s the question:

“A compound has four sets of 1H NMR peaks, four sets of 13C NMR peaks, and an ESI mass spectrum peak at approximately m/z= 93. What's the name of this compound?“

i’m having an irl version of “billy and sally disagree on the answer to this problem. who do you think is correct, and why?” - but i think it’s benzenamine/aniline but my friend thinks it’s phenol. there’s no answer key but this is a big part of our grade </3

is it either of those or are we both onto nothing? thank you reddit!

when i look at it, covalent catalysis is where the oxygen attacks the C=O. this happens after the step 2 arrow / product of step 2. so shouldnt it be step 3 because it begins at the product of step 2 and the result is shown after the step 3 arrow. furthermore, the acid/base catalysis arrow is is drawn at the same time the covalent catalysis arrow is drawn so i dont understand how covalent catalysis occures on step 2 and acid/base catalysis occures on step 3 when both arrows are drawn at the same time (between step 2 and 3 arrow)

EDIT: I'm seeing that this problem I made up is erroneous in all sorts of different ways so I'm asking that this post stops getting new responses. It was my fault for trying to make a problem out of something I didn't understand in the first place. I just took the example off of a pKa chart. Ultimately, I did figure out how to do my work.

EDIT 2: The Nitrogen in the acid/red should have a positive formal charge. I stole the example off of a pKa chart provided by my professor since it had a similar issue to what I was confused about, but the pKa chart was so faded the + looked -. I didn't notice. My apologies guys.

Basing this off of a homework problem I have, so I do apologize if this is crudely simplified. I can also give the real problem in the comments if necessary.

I’m using a pKa chart and estimating the pKa of molecules using functional groups.

Let’s say I have this blue molecule in the image. I see that it has a group which is a conjugate base of the red molecule. I know the red molecule is a strong acid, so the blue molecule is a weak base. Can I consider this molecule a base or neutral? Thinking this through for me at least, because it’s weak, it is unreactive, therefore neutral in an aqueous environment.

Now, the pKa. Can I say the blue molecule has a pKa=5.2 like the red molecule, or should I say the blue molecule has a pKaH=5.2? Or are both wrong statements?

If you’re screaming at me to do an acid-base review, yeah, I am doing one.