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Topic: Melting Point/Burning and Chemical Tests  (Read 1258 times)

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Offline Lucas B

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Melting Point/Burning and Chemical Tests
« on: January 23, 2019, 08:51:30 AM »
I was trying to do my research online and I was struggling trying to find any info about a chemical reaction involving Sodium Chloride, Sugar, phenyl salicylate, lithium chloride, sodium citrate, potassium chloride, ammonium nitrate, caffeine, barium sulfate, diphenylamine, cholesterol, and urea. I was trying to find out of which would have a chemical reaction when heated. I was given a mystery chemical (Out of those twelve) and I had to figure out what the chemical was. When I found there was no conductivity (by dissolving it in water and testing for conductivity) I knew that it was ionic. That means that there was only a possibility for the compound to be Sugar, phenyl salicylate, caffeine, diphenylamine, cholesterol, and urea. I then went to find the melting point for the mystery compound using a hot plate. I was unable to find it because as the hot plate was heating up, it turned a white and became a little more round. Then once the hot plate hit about 460 degrees Fahrenheit, the compound then turned golden brown then black. I can only assume that this was a chemical reaction but do you guys have any clue on what it could possibly be? I was thinking possibly caffeine but i'm not sure. And any ideas for other tests I should do to help figure out the compound would be appreciated. :)

Offline chenbeier

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Re: Melting Point/Burning and Chemical Tests
« Reply #1 on: January 23, 2019, 09:27:07 AM »
I think it was sugar. It is caramelized.

Offline wildfyr

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Re: Melting Point/Burning and Chemical Tests
« Reply #2 on: January 23, 2019, 10:56:20 AM »
If you dissolved it in water and it did not conduct, that means it was not ionic. Typo? I'm not sure I agree with your breakdown and ionic and nonionic compounds.

Offline Lucas B

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Re: Melting Point/Burning and Chemical Tests
« Reply #3 on: January 23, 2019, 02:30:09 PM »
What are some good ideas to identify compounds. Besides physical, what about chemical tests that I can do to identify the compound? Something that a school may have on hand? I did a flame test, density test, melting point test, and a conductive test. I am stumped because my compound is very general in all those tests. The flame test was orange. The density was 1. The melting point is unknown because its is having a chemical reaction while melting. The conductive test showed that it was not conductive therefore meaning it is covalent. I have narrowed it down to about 6 options. Any ideas? Sugar, Phenyl Salicylate, Caffeine, Diphenylamine, Cholesterol, and Urea. I think that it may be cholesterol but, any ideas to test that or to further find out what the compound is will be appreciated. :)

Offline jeffmoonchop

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Re: Melting Point/Burning and Chemical Tests
« Reply #4 on: January 23, 2019, 04:27:21 PM »
HPLC, GCMS, TLC. TLC might be easiest, Run your unknown next to knowns

Offline billnotgatez

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Re: Melting Point/Burning and Chemical Tests
« Reply #5 on: January 23, 2019, 05:32:21 PM »
I have merged your posts since they are similar.
We only post a given question once on the forum.
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Offline Lucas B

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Re: Melting Point/Burning and Chemical Tests (Look at Bottom Comment)
« Reply #6 on: January 23, 2019, 07:07:33 PM »
HPLC, GCMS, TLC. TLC might be easiest, Run your unknown next to knowns
How exactly would I be able to do this to identify my compound? Are there any unique traits that I could find in the chemical tests? Or what chemicals should I use for a chemical test and what would help identify the compound? If it is easier, what other physical tests should I do to help draw my conclusion of the compound?

Thanks so much,
Lucas

Offline hypervalent_iodine

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Re: Melting Point/Burning and Chemical Tests (Look at Bottom Comment)
« Reply #7 on: January 23, 2019, 08:14:20 PM »
HPLC, GCMS, TLC. TLC might be easiest, Run your unknown next to knowns
How exactly would I be able to do this to identify my compound? Are there any unique traits that I could find in the chemical tests? Or what chemicals should I use for a chemical test and what would help identify the compound? If it is easier, what other physical tests should I do to help draw my conclusion of the compound?

Thanks so much,
Lucas

Measuring the pH to determine whether or not it’s acidic, basic, or neutral will help you knock out a lot of possibilities. You could just do it with pH paper if you don’t have a probe. Make sure you also take a reading for water if you do it.

Offline Lucas B

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Re: Melting Point/Burning and Chemical Tests
« Reply #8 on: January 23, 2019, 08:28:50 PM »
Thank you, after I do that, do you have any ideas for a specific test that I can use to be able to find the unique compound. I keep getting to a point where they get to be very similar and I was wondering if there would be something specific I can do to be able to tell the difference most (or all) of them. Possibly any acids I should mix with to get a specific reaction to the compound? Idk i'm sorry for asking for so much help but this is probably the biggest grade all year.

Offline hypervalent_iodine

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Re: Melting Point/Burning and Chemical Tests
« Reply #9 on: January 23, 2019, 08:54:51 PM »
You should also be able to eliminate a few others based on solubility. If your compound dissolves in water, there are a few things in that list it won’t be. You could also try dissolving in a few organic solvents like ethanol, acetone, or chloroform to get a better idea of solubility (which would also help confirm your conductivity result). There are some chemical tests you could do for some of those compounds once you have it narrowed down. I assume this is high school, so could you tell me what sorts of chemicals you have access to? And what level chemistry are you in / what are you learning about at the moment?

Offline Lucas B

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Re: Melting Point/Burning and Chemical Tests
« Reply #10 on: January 23, 2019, 09:34:42 PM »
This is highschool and I have access to most chemicals. We normally use not so acidic chemicals but, if I ask with her supervision I can probably use more acidic. I am in chem right now and just finished learning about polyatomic ions. What chemical tests do you recommend that I do?

Offline hypervalent_iodine

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Re: Melting Point/Burning and Chemical Tests
« Reply #11 on: January 24, 2019, 02:06:57 AM »
I'm not going to give you all the answers! I would strongly recommend you construct some sort of flow chart for identification of all of your compounds. Start with pH, and separate the compounds by whether they are acidic, basic, or neutral. Then look at the compounds in each group, think of some property that might separate them further (maybe conductivity or solubility, maybe something else), and repeat until you have a clear path for identifying each compound. If you look it up online, you will find a lot of examples of what I mean. I had a go at making one myself, and I think you can come up with something mostly using methods that have already been mentioned here, or that you yourself have done.

Offline Lucas B

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Re: Melting Point/Burning and Chemical Tests
« Reply #12 on: January 24, 2019, 07:18:56 AM »
Okay thanks for the help, this helps a lot

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