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Everything posted by Technologist

  1. Here is an interesting question. Suppose you have to prepare a half liter of 10^5 ppm solution of Iron in 15% HCl using Ferric chloride hexahydrate. So (10^5 mg/L Fe) x (0.5L/1) x (1g/1000mg) x (~270g FeCl3*6H2O/~55g Fe) = ~ 245g of FeCl3*6H20. Now my question is. How much concentrated HCl (lets say 35%) should I be adding to get a 15% solution ... taking into consideration the hexahydrate is going to be taking up space?? I have an idea myself but I'd like to see how others come up with a solution as well. Thanks guys/gals.
  2. Until you acquire enough experience with the various indicators its best to titrate at a rate of a drop or two per second until you see you are nearing the endpoint. When you are nearing the endpoint slow down the rate at which you are adding titrant. You can add a drop, swirl the Erlenmeyer, add another drop, swirl, etc. You can even add a half drop and touch the inside of the Erlenmeyer to the hanging drop. Just make sure to tip the Erlenmeyer to collect the titrant that’s holding onto the sides of the Erlenmeyer. A rule of thumb to remember during analytical work is you’re chasing molecules. If you eventually pursue chemistry as a profession it’s important to realize that your company is paying you per hour. They want to get as much work out of you in that hour as possible. So you can’t titrate at a rate of a drop per second. What I’ve learned to do is open the stopcock to allow a slow stream of titrant into the flask. I swirl the flask once every couple seconds. When you are near the endpoint you’ll see the color starts to hang around longer than usual. That’s when I slow down and add drop by drop. Lastly, burets are most accurate in the middle range of the graduations. So a 50mL buret is most accurate around the 20-40mL mark. As for your calculations it appears to be common practice for chemistry students to memorize formulas. I’d rather see teachers teach students a tool called dimensional analysis. Here is how I’d workout the problem. Now I found your original paragraph above a bit confusing so I hope I understood correctly. 18.32mL x ( 0.08045moles NaOH / L ) x ( 1mole HCl / 1 mole NaOH ) x ( 1/25mL HCl ) = 0.059 M HCl. Below is a decent link. http://www.chem.tamu.edu/class/fyp/mathrev/mr-da.html
  3. In our lab we mostly use plastic beakers made out of polypropylene. They are disposable, reusable, cheaper, and quite durable. If you look around online you'll be able to find some good analytical balances at online jewelry stores, diamond dealers, etc.
  4. Hello. I'm looking for a instrumental analysis textbook on spectroscopy and electrochemistry. If anyone has any good recommendations please post them up. I have a number from Skoog and would like a few others. Thank you for your efforts.
  5. I don't know what you mean exactly. Perhaps something like a Grignard reagent?
  6. Hey thanks a lot guys. Chromatographer … you got me there. I’m aware that it’s an instrument used in labs and not necessarily a specific career designation. I’m curious to know what you guys think about specializing in chromatography. My program head offered me a job out of school with a company that does various “analytical contract work” with chrom. Basically my job would be to fly out with a disassembled chrom, set it up, perform an analysis, troubleshoot, etc, and fly back home. It would be a good experience. I am hoping that becoming skilled in chromatography would lead to a good career down the road with a petrochemical company (Albertan here). Sorry about the confusion.
  7. A few more months here and I'll be finishing up my program. Over the past while I've developed an interest in chromatography. I'm curious to know if anyone has any experience in the chemical industry and can offer some advice. If there is a lot of work, if its worth it to pursue chrom in the long run, in general what people are thinking. I would eventually like to work in the petrochemical industry (I live in Alberta which pays well at the moment).
  8. I have to identify an unknown liquid. Smells a bit like tiger balm. Refractive Index of 1.5167 @ 22.5 degrees C. Infrared Spec: I have the big broad obvious OH stretch. Two strong peaks around 700 & 750 which is characteristic of a mono subst' benzene ring (NMR shows a big ass (5x) peak at 7.2). C-H stretching. And what I think is a C-O stretch of a primary alcohol. UV-Vis: Lambda max @ 260 nm. Problem is that I'm no NMR expert. Its up to me to learn. I need a good tutorial web site. If anyone can help me out on the basics of chemical shift, etc would be appreciated. I want to figure it out on my own, only way I'm going to learn, but I can provide scans of the NMR. Specifically I have to figure out the configuration of the molecule.
  9. C Slave you should spend a few moments of your time learning about logical fallacies. Specifically "stolen concept". Basically you are stealing concepts out of their contexts and applying them to contexts that don't fit. In other words, you are copy/pasting concepts to situations that don't apply. As a result people are having a difficult time understanding you (words only have meaning in a specific context) and you are committing many errors in your scientific thinking. As you get older and (hopefully) acquire more training in science and communication, you'll understand the value behind proper structure in science and communication. I mean what's the point in visiting a message board if no one can follow what you are saying?
  10. I would suggest you stop trying to explain everything through bubbles and pick up some basic physics and chemistry books ... unless you want to be called a bubble head.
  11. Hey guys/gals. I have two big reports ahead of me for finals. First, I have to determine the % Sb in a sample of tartar emetic by an iodimetric titration process. Second I have to determine the mass of Cr in an unknown chromate sample by iodometric titration process. If anyone has any good web sites/books/etc that explain the theory behind iodi/iodometric titrations that would be great. Thanks a lot !!
  12. I like to extract and purify oils/fats from plants. But the one reaction that changed my path from biology to chemistry is the reaction of Na + Cl --> NaCl. It looks disturbing knowing the value of sodium chloride in the body.
  13. By the way its very difficult to increase your muscular mass. The average individual with average genetics may put on 20lbs in a life time of lifting. I lift 5 days a week at 630 in the morning. 90% of the regulars I see lifting are not big at all. They just look fit.
  14. All you need to do is squat, chin, and do some pushups. See if you can work your way up to doing 500 squats in a row. After you get 500 try and do it with a gallon of water in a back pack. Chins you should be able to find a spot. Any spot that you can pull yourself up. See how long it takes you to complete 40-50 reps. Chins work your back, chest, shoulders, biceps, and forearms. Pushups. If needs be, get a partner to sit on your back. Leg Raises. In the hanging chin position lift your knees up to your chest. A good workout is to do a set of squats, chins, pushups, and leg raises and repeat until you are exhausted. Two-three times a week.
  15. Sorry, that was a mistake. I understand that intelligent design is not a theory in the scientific sense. Its not based on experimentation. I was just referring to it as a theory out of habit (popular use of the term). I agree. When I first starting studying biology I was under the impression that evolution did explain the origin of life. Later I came to realize that it does not. Swansont what explanation for the origin of life do think is plausible?
  16. What convinced you that there is not a god? What reasons do you not believe in the supernatural? I think you need to check your premises. It would appear from your post that your decision has been made with little training as a scientist and little education on evolution. If you are interested in the truth, if you want to be objective, then shouldn't you consider all options? I'm not suggesting that you have to grant plausibility to every idea, but consider that your current definition of god may not fit with reality. Thats one angle. My training is in chemistry and I was surprised to find a number of biochemistry professors who believe in the intelligent design theory. Now I'm not suggesting that someone with a PhD is infallible, but someone with a PhD in biochemistry is at least informed and capable of making reasonable decisions. Myself I am an atheist. I believe that evolution does explain the origin of species, but I'm not convinced that it explains the origins of life.
  17. Nathaniel 25yrs Yes on 6 of the 8 fingers.
  18. A good rule of thumb for a quick estimate of boiling points, and I hope I explain this well, is to consider every: carbon as 1 chlorides as 2.5 ethers as 1 primary amines 2.5 secondary amines 1.5 tertiary amines 1 alcohols 4 aldehydes 2.5 ketones 2.5 nitriles 4 acids (O + OH) 5.5 Esters (O + O) 2.5 Anhydrides 4 Acid Chlorides (O + CL) 3.5 Amides (O + NH2) 10 Diethyl ether has four carbons and an ether. That’s 4 + 1 = 5 Ethyl alcohol has two carbons and an alcohol group so 2 + 4 = 6 Therefore you would predict that ethyl alcohol has a higher boiling point than diethyl ether. It’s a crude yardstick at best but works in most chem labs.
  19. I asked a friend of mine in a lab who is obsessed with alcohol, he mentioned that you could use calcium oxide to distill the azeotropic mixture, but you'd have to bake the calcium oxide (standard oven time is 1 hr at 110 in our quant labs but its often depends on the cpd) and store it in a vaccum dessicator. Then reflex ethanol and calcium oxide for several hours, let it sit overnight, then distill. Not sure if this works or not ... he's kind of a nut. Also you'd probably want some pure calcium oxide ... you can never be sure what impurities remain. I do know that you can distill absolute ethanol with benzene however its not fit for human consumption.
  20. Much of what I've read in astronomy suggests that the concentration of matter in space is largely diluted. There is not enough material (medium) to transmit waves. If I recall correctly this is why scientists invented the mysterious ether. Is this incorrect?
  21. Pretty much any disruption in homeostasis can lead to an increase in hGH production, such as exercise. The production of testosterone is governed by a negative feedback system in your body.
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