aommaster Posted September 20, 2004 Posted September 20, 2004 Hi guys! Well, I did well in my GCSEs and nowm I have gone to do A level chemistry, physics and maths! Well, I asked my teacher on what would be produced if you boiled off the water in sulphuric acid, since it is AQ. She didn't know and told me to boil it so she could find out. Even after the experiment, she didn't know, so question one is, what WOULD be produced? Now, while I was boiling it, it was boiling like normal water until the end where there were about 10cm3 left. It went stable. So, I took out a stirring rod, and started to stir it. Bubbles suddenly erupted from around the rod. When I removed it out, the bubbles stop, when I put it back in, it bubbles again. I think this is the effect of super-heating, but I am not sure. What was happening? That's the second question! Then, the exiting part (and scary), 5 minutes after more heating, white smoke started to erupt from the beaker. It has a sharp smell to it, like the smell you get from HCl and Chlorine, but, it was worse. We had to take the beaker outside and empty the chemistry lab!!! (Only a friend and I were there, so, not a lot of hassle!). What was that smoke that was produced? And how was it formed? Those are questions 3 and 4! Finally, after the smoke stopped, I examined the beaker and there was a yellowinsh liquid in it. It was transparent, but yellow. What was that liquid? Was it concentrated sulphuric acid? That's the last question! Thanks alot guys! MY first lesson in a chemistry class seems like a fairytale!!!
bloodhound Posted September 20, 2004 Posted September 20, 2004 It seems to be most pple teaching chemistry are not qualified enough. Luckily we had only one Brilliant Old Experience Geezer. who could teach Physics and Chemistry and had answers to all of your questions. He could have been a Uni lecturer. so every other chemistry and physics teacher used to run up to him everytime they encountered a hard question
aommaster Posted September 20, 2004 Author Posted September 20, 2004 Hehe, so, do you know any answers to my adventure?
Gilded Posted September 20, 2004 Posted September 20, 2004 *Sigh* I only have done stuff with H2SO4 during a chemistry lesson once in my life, and it was 5-10% or something. About the yellow color: Isn't superconcentrated sulfuric acid just plain transparent, without the shade of yellow? Could it be that with enough heat H2SO4 says "screw this, I'm outta here" and turns into water vapor (H2O) and sulfur trioxide which causes the yellow shade? Since I don't think H2SO4 maintains its molecular form when it becomes gaseous. Or maybe it does. Heck, maybe it's just better to ask YT.
aommaster Posted September 20, 2004 Author Posted September 20, 2004 Those are only my guesses, and I am only at the start of my AS course, so, don't take my word for it. Wolfson, YT2095 and other big posters on SF will know. Not me!
boris_73 Posted September 20, 2004 Posted September 20, 2004 boiling sulphuric acid untill dense white fumes comes off gives it about a concentration of 98% then you stop boiling the yellow tint might be the sulphur breaking down if you have heated it to long thats all i can say about the yellow tint it may be wrong or unless it had some impurites in the glass you used or the sulphuric acid, but the dense white fumes is the sign that its about 98% concentrated
aommaster Posted September 20, 2004 Author Posted September 20, 2004 Ok, so that is what would be left, answer to question 1 and 5. Thanks Boris. But what about these: 2.The bubbles that formed awkwardly during boiling 3.What are the fumes made of? 4.How was it formed?
Gilded Posted September 20, 2004 Posted September 20, 2004 Even with minor impurities on the glass, you will most likely see bubbles when sulfuric acids attack them (depends a bit on the impurities though). That's why H2SO4 is good for cleaning test tubes and such.
aommaster Posted September 20, 2004 Author Posted September 20, 2004 There were no impurities on the glass. And even if so, why didn't it fizz when I poured it in? Also, this only happens when I touch the surface of the sulphuric acid with a stirring rod.
boris_73 Posted September 20, 2004 Posted September 20, 2004 oh yes what you have taken for as courses i took similar ones biology chemistry and maths unless you understand them clearly and you are very good at the subjects i would advise you dont take them they are nothing like GCSE's they get much harder
aommaster Posted September 20, 2004 Author Posted September 20, 2004 Hehe, I understand chemistry physics and maths very, very well! You don't have to worry. And besides, they are my favourite subjects!
Gilded Posted September 20, 2004 Posted September 20, 2004 I meant that there were impurities on the glass rod, if bubbles formed when you put it in the acid. That seems like an acid attack to me.
boris_73 Posted September 20, 2004 Posted September 20, 2004 it most probably was an acid attack due to impurites on the glass rod which caused the bubbling
Gilded Posted September 20, 2004 Posted September 20, 2004 Yep, and I really believe that the yellow color is from SO3, since H2O and SO3 can form H2SO4, so it makes sense.
aommaster Posted September 20, 2004 Author Posted September 20, 2004 But it wasn't fizzing, it was acutally bubbling like when you boil water. And it only happened when there was very little h2so4 left. Yeah, and I agree with the fact that it could be SO3. Isn't SO3 a gas?
Gilded Posted September 20, 2004 Posted September 20, 2004 Hmm, I think it is. Is it possible for it to break up into a sulfur atom and an ozone molecule? Or SO + O2? I don't think SO is a gas. And about the bubbling, if it's really conc. H2SO4, it's as vicious as a rabid wolverine and attacks anything it can. It might also be that the yellow came from the impurities.
aommaster Posted September 20, 2004 Author Posted September 20, 2004 But, why wouldn't it attack the impurities in the glass rod from the first time I started to stir it? It only started after there was very little liquid left. Could this be a possibility because of the varying concentration?
boris_73 Posted September 20, 2004 Posted September 20, 2004 because it may have not been concentrated enough to do it the first time
boris_73 Posted September 20, 2004 Posted September 20, 2004 and i am very supprised your teacher did not no this maybe he did not want to tell you.
aommaster Posted September 20, 2004 Author Posted September 20, 2004 Well, beleive it or not, she said that it was strange. I am pretty sure that the stirring rods were clean. Could it have reacted with the dust on them? That, could then be possible!
boris_73 Posted September 20, 2004 Posted September 20, 2004 it was most probably some other chemical on it used in a previous experiment and not washed propley at my college that happend quit often and so we made sure we washed the appiratus when we came to use it other wise the experiments would be ruined eg titrations
aommaster Posted September 20, 2004 Author Posted September 20, 2004 So, that's the bubbling bit solved. So, what is the reaction when heating? H2SO4 ---> H2O + SO3 ???
Gilded Posted September 20, 2004 Posted September 20, 2004 Hey, are you sure it wasn't a PLASTIC rod. Or some crappy glass. "H2SO4 ---> H2O + SO3" I'm almost certain, because that's the way it's formed.
aommaster Posted September 20, 2004 Author Posted September 20, 2004 Oh, ok. Thanks alot Glided for your help!
Gilded Posted September 20, 2004 Posted September 20, 2004 No problem. It would be nice to have this confirmed by YT or someone who knows more about this stuff, though.
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