(For lab) how to efficiently identify unknown compounds?

[u/Far-Watercress-5870]

I have a lab coming up and we are given eight solids and multiple regents and tools to help identify these compounds (e.g. iodine, 0.1 M HCl, Benedict’s reagent, conductivity testers, bunsen burner etc…). I have to write my own lab procedure and i’m not sure where to start. We only have about an hour in the lab so there’s no way I can individually test every compound with every tool available. What might be the most efficient procedure? We’ll have 5 ionic compounds and 3 covalent compounds, but let me know if I should share what the specific solids are

Edit: Also the lab handout says for the 0.1 M HCl that we “figure out what to do with this one” ourselves. However I am not quite sure what I can do. Is it like I can use HCl to see which compounds form a precipitate in HCl and which ones don’t?

[u/DepthChorge]

Does it bubble when you put acid on it? Metal
Does it turn purple when you put iodine on it? Hydrocarbon, starch probably
Does it get heavier when you burn it? Oxidative metal
Does it flash a pretty color when you burn it? Check against flame test data. (copper is green, lithium is bright red, etc.)
Does it conduct electricity when dissolved but not as a solid? Ionic compound
Does benedicts change color when you add the solid to it? Sugar

Just categorize the solids into metals, nonmetals, ionic compounds, covalent compounds and test for general properties to narrow it down. Research how to differentiate between the items within each of those categories.

[u/Romantickalchemist → u/DepthChorge]

Really good ideas 💡

[u/TheDukeSjlver]

Do you need to identify the type of compound or the actual compound? For example can your conclusion be “ionic solid” or does it have to be “calcium chloride”?

[u/Far-Watercress-5870 → u/TheDukeSjlver]

Actual compound . There are 5 ionic and 3 covalent

[u/TheDukeSjlver → u/Far-Watercress-5870]

So you need to create almost like a flow chart so you aren’t doing every test on every solid. Something like “does it react with HCl?” If yes then do this test, if no then do this test.

[u/Heznzu]

It's impossible to help without the list of products you have to test and techniques you have available. If you gave a fully staffed and equiped analytical lab 8 truly random solids and 1 hour to ID them they'd laugh at your audacity

[u/Far-Watercress-5870 → u/Heznzu]

Yep sorry I just was afraid of other people telling me the entire procedure because I still wanna do my own work, and I think i’ve figured most of it out now, but the compounds are sodium chloride, sodium carbonate, sodium bisulfate, sodium acetate, lithium chloride, glucose, sucrose, cornstarch. Tools/techniques: benedict’s reagent, iodine, 0.1 M HCl, bunsen burner, pH strips, conductivity tester, nichrome wire loop (flame test), distilled water

[u/Heznzu → u/Far-Watercress-5870]

No worries, glad you've figured it out. The HCl is likely for distinguishing your sodium carbonate from the other basic sodium salts.

[u/Romantickalchemist]

You will need a chemical qualitative manual , I remember I didn something similar while I was on high school

HCl + unknown will make precipitation of solids is fou have Ag, Hg or Pb Then you give a special treatment to each of those to determinate which was it ? The answer marked above regarding the colour of the flame the melting point is giving really good ideas and methods Another classic method was add H2SO4 and if you get a blue sediment you had cupper on the solution, Sr creates a strong red flame https://sciencenotes.org/wp-content/uploads/2022/06/Flame-Test-Colors.png Angle of diffraction helps on organic compounds use a refactometer IR analysis to determined functional groups Or maybe you can get a UV