Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: 1QWK96GT on November 04, 2013, 04:09:06 PM
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Hey everyone I am new here. Currently I am in college taking Chemistry 112 I am new to all this so please bear with me. My Chemistry 112 professor wants us to do a science experiment in front of the class which I have no problem doing. We have to choose a topic/experiment and somehow better its effects. I decided to go with a Glow solution. (pretty simple). Anyway he wanted us to gather a list of needed ingredients which I did. I was checking to see if they had the chemicals I would need and they had them all. The ingredients list I found online (http://www.wikihow.com/Make-a-Glowstick) calls for 50 mL of Hydrogen Peroxide, 1L of distilled water, .2 grams of luminol, 4grams of sodium carbonate, .4 grams of copper sulfate, and .5 grams of ammonium carbonate, and another liter of distilled water. Well the chemistry lab had everything except copper sulfate, instead they have Cupric Sulfate Pentahydrate. The professor said the Cupric Sulfate Pentahydrate could be used to substitute the Copper Sulfate. I recalculated the amount needed which I figured .4grams of Copper Sulfate would be about .31 grams of Cupric Sulfate Pentahydrate. I started mixing all the chemicals together under the hood and I realized I did not want to make that much solution. I am only making enough for people to visibly see I dont need 2 liters of the stuff. So I reduced the amount of solution from 2 liters to 1 liter and put in the chemicals. All it did was fizz/smoke (exothermic) and I got no glow. It was a black/brown liquid that smoked with no glow? I was wanting to know what did I do wrong? How can i make a much smaller glowing solution that will definitely work with the chemicals I have. Ohh and incase you were wondering I was going to take it one step futher and make two beakers of the solution. Put one on a hott plate and the other on ice(or room temp) and my theory is the on on the hott plate will glow more intense but not last as long as the one on ice or at room temperature.
Any advice?
Thanks alot guys
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In what order have you mixed them?
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just two remarks:
to start with the obvious:
I recalculated the amount needed which I figured .4grams of Copper Sulfate would be about .31 grams of Cupric Sulfate Pentahydrate.
you miscalculated badly here
ref. your idea "hot plate": don't heat H2O2 solutions, as it will decay rapidly
regards
Ingo
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First I took 50mL of Hydrogen Peroxide and mixed it with 500mL of distilled water. Then first I added .2 of luminol, 4 grams of sodium carbonate, .31 grams cupric sulfate pentahydrate, .5 grams ammonium carbonate into the first mixture. So I should not use a hott plate with cupric sulfate pentahydrate? is there anything I can substitue since the campus does not have copper sulfate.
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Cupric sulfate is a synonym of the copper sulfate. And don't worry about the pentahydrate part - even if you will use anhydrous salt copper would become hydrated after dissolution. My bet is the procedure calls for 0.4 g of the pentahydrate, as it is the most popular copper salt available.
At these amounts of carbonates pH of the solution will be around 10.4, so no doubt copper hydroxide will precipitate - initially it should be blue, but then it decomposes into CuO, which is brown black. That sounds plausible as an explanation to what you have observed, not that it helps with making the glowing solution.
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Cupric sulfate is a synonym of the copper sulfate. And don't worry about the pentahydrate part - even if you will use anhydrous salt copper would become hydrated after dissolution. My bet is the procedure calls for 0.4 g of the pentahydrate, as it is the most popular copper salt available.
At these amounts of carbonates pH of the solution will be around 10.4, so no doubt copper hydroxide will precipitate - initially it should be blue, but then it decomposes into CuO, which is brown black. That sounds plausible as an explanation to what you have observed, not that it helps with making the glowing solution.
Okay so your saying just use .4 grams of the cupric sulfate pentahydrate in substitution for the .4 copper sulfate it calls for? I feel I am going to fail this experiment because that thing did not glow like i thought it would. I did get frustrated and dumped some hydrogen peroxide in it (after I deemed the experiment was not working) and I noticed everywhere the hydrogen peroxide was entering the solution was glowing but quickly dissipated into the brown/black abyss.
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Also, to preserve reagents, I would do it on a much smaller scale until until you get it to work right.
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The glow from luminol is fairly faint. Make sure you have the room lights off when you're trying to observe the glow.
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The glow from luminol is fairly faint. Make sure you have the room lights off when you're trying to observe the glow.
Its funny you mention that. i was wondering because I did only cut half the lights off in the room and didnt see anything so thought it wasnt working. I did not want to be rude and cut all the lights off while other students were doing their projects. If I were to mix less solution should I just use the same amount of the chemicals? essentially dial down the hydrogen peroxide and distilled water but keep the ammonium carbonate, cupric sulfate pentahydrate, luminol, and sodium carbonate amounts the same?
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Also, to preserve reagents, I would do it on a much smaller scale until until you get it to work right.
Yea thats what I was hoping someone would help me with. I dont need near that much solution in the end because I am not dishing it out to the students it is only for them to observe.
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When I did this reaction for a demonstration, this is the approximate procedure I used:
http://chemistry.about.com/od/glowinthedarkprojects/a/luminolblood.htm
And personally I didn't find the fluorescence faint. The lights were turned off for effect in our demonstration, of course, but if it's so faint you can't see it, then you've probably done something wrong, or you're working at concentrations that are too dilute.
EDIT: I like the idea of adding fluorescein, a ubiquitous fluorescent dye, as suggested in the link above. That sounds like it could be really cool and I may have to try it myself...
EDIT2: When we did this demonstration for a bunch of kindergardeners, we mixed the solutions in the back of the room and let them drain through a long, transparent tube to the front of the room (it was in an auditorium, so the back of the room was raised compared to the front). This made for a very vivid display.
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When I did this reaction for a demonstration, this is the approximate procedure I used:
http://chemistry.about.com/od/glowinthedarkprojects/a/luminolblood.htm
And personally I didn't find the fluorescence faint. The lights were turned off for effect in our demonstration, of course, but if it's so faint you can't see it, then you've probably done something wrong, or you're working at concentrations that are too dilute.
EDIT: I like the idea of adding fluorescein, a ubiquitous fluorescent dye, as suggested in the link above. That sounds like it could be really cool and I may have to try it myself...
Wow that sounds neat. I am going to try the one you listed but now I need to tell the teacher to get (potassium ferricyanide or a sterile blood lancet and sterile alcohol pad and 15 g potassium hydroxide) I hope my teacher will get these ingredients because I already gave him my list of ingredients for the first one I attempted. I know he will laugh when I say I need fresh blood. I am not sure a college chemistry class can order fresh blood. Or maybe I could buy some meat and drain the blood in a container to keep it fresh? Thanks so much for the link hopefully that one will work because the one I was trying has failed me miserably.
EDIT2: When we did this demonstration for a bunch of kindergardeners, we mixed the solutions in the back of the room and let them drain through a long, transparent tube to the front of the room (it was in an auditorium, so the back of the room was raised compared to the front). This made for a very vivid display.
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What I would do is do everything in the experiment I suggested, but use copper sulfate instead of the ferricyanide. Copper should also catalyze the reaction well. Make sure you scale the masses appropriately because the ferricyanide will have a different molecular mass than copper sulfate. If it works, you're golden. If not, you have something to fall back on, and most decently equipped chemistry labs at a university should have ferricyanide - which is the traditional reagent and will definitely work the best. And like I said, until you get it to work, cut the scale down by an order of magnitude (divide everything by 10). This way you don't waste a lot of materials.
(Don't worry about the blood lancet. It'll work with the iron salt for sure. If it doesn't, something's wrong and the lancet isn't going to help.)
EDIT: A word of warning, though: don't mix the ferricyanide with a strong acid, unless you fancy breathing in some HCN gas.
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What I would do is do everything in the experiment I suggested, but use copper sulfate instead of the ferricyanide. Copper should also catalyze the reaction well. Make sure you scale the masses appropriately because the ferricyanide will have a different molecular mass than copper sulfate. If it works, you're golden. If not, you have something to fall back on, and most decently equipped chemistry labs at a university should have ferricyanide - which is the traditional reagent and will definitely work the best. And like I said, until you get it to work, cut the scale down by an order of magnitude (divide everything by 10). This way you don't waste a lot of materials.
(Don't worry about the blood lancet. It'll work with the iron salt for sure. If it doesn't, something's wrong and the lancet isn't going to help.)
EDIT: A word of warning, though: don't mix the ferricyanide with a strong acid, unless you fancy breathing in some HCN gas.
Thank you so much for the help I always put safety first especially in the lab (I was actually going to ask if my first list of ingredients would yield something hazardous to breathing) (I dont want to mix a solution that is going to be putting off dangerous fumes for me.) So I should just stick with the cupric sulfate pentahydrate? instead of the ferricyanide? How do I find the amount of cupric sulfate pentahydrate I need?
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I forgot to ask one more question with your experiment would I be able to heat one on a hott plate and the other just have at room temperature and the one on the hott plate would glow more intense but for shorter period of time? While the one at room temp would not glow as bright but for a longer period of time? I have to demonstrate this in class.
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Potassium ferricyanide will probably work best. This is the traditional reagent used for laboratory demos, with a strong hydroxide base and peroxide of course. If you can find some, I would recommend it. As I said, many well equipped chemistry labs will have it in stock.
If you can't find ferricyanide salt, then you can try the copper salt as a substitute. It SHOULD still work, but I don't know if it will work as well. I'm not sure how well copper catalyzes the reaction compared to iron. But, it can't hurt to try.
You basically want to ensure you're using the same number of moles of your copper as you are of your iron. So you'll need to find out how many moles of potassium ferricyanide the recipe is asking you to use, then find out how many grams of copper sulfate hydrate you need to substitute to give you the same number of moles of copper.
If you heat it up, the reaction should be more intense but not last as long. However if you're not going to be doing this in a hood, I would suggest you do not heat an open system of strong base and peroxide on a bench. If you need to show the effect of temperature, consider having a second one that you cool down - it should dim and last longer, the same way you can preserve halloween glowsticks by sticking them in the freezer.