r/chemhelp

I don’t know who to ask for advice because I don’t know anyone who’s taken it before

For my last college lab experiment we were tasked with creating our own procedure to identify an unknown food dye from a melted red, orange or pink Freezes. It's designed so there's only one food dye for students identify, however my prof said she was confident my partner and I could attempt the more challenging version of this lab, identify multiple dyes in a green Freeze. Alongside the identifying the LOD, LOQ, either the %(w/w) OR %(w/v), the "quality" of our data, and whether or not the data is "reportable."

We found brilliant blue at 632nm (blank-corrected ABS of 0.320) & tartrazine yellow at 414nm (blank-corrected ABS of 0.259) through a multi-wavelength scan of a diluted green Freeze sol'n (20.0mL diluted to 100.0mL). We did a calibration curve for known concentrations of brilliant blue (2, 5, & 10ppm; 792.85g/mol), and for known concentrations of tartrazine yellow (2, 5, 10, & 20ppm; 534.36g/mol).

Here's where my partner and I are confused: we only measured absorbance of brilliant blue at 632nm, and absorbance of tartrazine yellow at 414nm, and the formula she sent us appears to need an absorbance readings of both yellow and blue dyes at both the identified wavelengths to calculate the absorptivity for both yellow and blue at the identified wavelengths, 414nm and 632nm. Or is it possible for us to calculate the missing absorptivity values from the data we collected? Is it possible for us to report anything?

I've attached a screenshot of the formulas provided to us (from a similar lab procedure, but identifying caffeine and benzoic acid/sodium benzoate).

https://preview.redd.it/2p8273grj9tg1.png?width=648&format=png&auto=webp&s=4d26c8d077ef305d9278ce34642d73849db7b6f6

https://preview.redd.it/2cgaica6g9tg1.png?width=678&format=png&auto=webp&s=d4b353929473bf81aee3c673e7a20f6a42875a07

Please let me know if more info is needed, I have an excel sheet with the current calculations done thus far.

https://preview.redd.it/nokp579onatg1.png?width=988&format=png&auto=webp&s=5cac52f53ea8d255d8a1f3ac906bb47dc573bf90

Normally, we would write the equation and then use countless other ways to calculate the answer, but I need a quick solution method and a way to think through these things??? Especially when it comes to essay questions.

https://preview.redd.it/na6nzfz1w7tg1.png?width=1158&format=png&auto=webp&s=797ddc443784b763fbc1739c5a043d7d2efd4d58

https://preview.redd.it/vooiysn3w7tg1.png?width=955&format=png&auto=webp&s=8d5f0746ba03a76e3ee392e732dee55577e29ebf

To my understanding I know that one hydrogen gets replaced by one of the Br Or CL and that this is hydrolagation something like that

Hi everyone! I’m planning to take an online Chemistry class this fall at Wake Tech, and I’m trying to decide between Peter Heffner and Dominic Ali.

I’d love to hear from anyone who has taken either of them, specifically regarding:

• How organized and navigable are their Blackboard/online course materials?
• Are they easy to reach if you have questions?
• Do they provide helpful materials, extra practice, or study guides online?
• Are they lenient grader and provide extra credits?
• How is their pacing, clarity, and approach in an online setting?

I just want a good visual of what the online class feels like and a better understanding of how each professor handles it. Any insights or advice would be super helpful!! Thank you!!

Hey everyone! I am currently working in a program that needs some precision and I need to correlate Molarity to weight%.

I want the user to input the molarity of HCl and use a library to calculate other stuff, the thing is that the library uses wt%, (I have to input it as % of HCl and % of H2O).

From what I know I shouldn't really be able to make arbitrary conversions and would need a table with reliable data.

Is there any reliable source for this?

So basically was pre med, now a nurse but I need to do organic chemistry for grad school. So far I found a DAT anki flashcards that has general chem and orgo, and so far its been fine, ive been like 'oh i remember that'.

Im planning on finishing the anki deck and just quizzing myself with khan academy and some chemistry textbooks practice questions. Then once I think im good like getting 90%+ on practice tests, ill start reviewing orgo just since im not a trad student and its been like 3 years since I last took Gen chem 2. Just looking if thats a good plan or not

I am assigned to take in charge of phosphating pretreatment production process. And there is one project for me to study. I’ve never got any experience in controlling chemical processes before. But as far as I study the process I acknowledge the long heat up temperature in phosphating tank.

The tank got a lot of sludge precipitation even there is a system design to flow back and forth from 16 m3 settling tank with no circulation, only overflow subtank and 34 m3 production tank with 40 L/min circulation pump and heat exchangers to help keeping the temperature constant.

Luckily the previous technician in charge of this process build a sludge hydraulic press machine. I comes to the solution to use press equipment but only allow to operate on the optimal condition where I need to measure clogged up sludge amounts during the week and set up the routine for this operation.

How do I precisely or at least approximate the sludge amount In tank system? Is there an effect of fresh phosphate chemical and chemical with long time used?
Is there any practical way to represent the rate of sludge phosphate precipitation when comparing on the timescale between newly buildup zinc phosphate chemicals vs long time used (a month or two) of phosphate zinc tank.

If I have only tritrate lab to test for free acid in control range can I use it to reflect anything about its precipitation rate calculated?

I have an Orgo 1 exam coming up and I need help with deciding whats the better path. The next exam is 12 days away and its on 3 chapters of lectures.

Here's the situation:

For a couple of weeks in the semester I was hospitalized with pneumonia and I missed the first exam. My professor was super understanding and he's gonna drop that exam grade. The problem is that there's 2 exams + the Final left so its much more important that I get an awesome grade on them.

Since the class is for ORGO 1, I thought it would be better if I started from scratch (since orgo is cumulative) BUT with 12 days left until the next exam I don't know how feasible it is to master 7 chapters of organic chemistry. Studying only the 3 chapters (ch. 5-7) sounds like the better idea but since i'm already behind i'm still kind of lost on the topics. Aaaah! I just really really want to get an A on this exam.

Our chapters are on Klein's textbook:

1. Gen Chem Review 2. Molecular Reps 3. Acids/Bases 4. Alkanes and Cycloalkanes 5.Stereoisomerism 6. Chemical Reactivity 7. Nucleophilic Substitutions and Elimination