Chemical Forums

Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: HerrSwampy on October 11, 2022, 12:46:53 PM

Title: Identifying unknown chemical
Post by: HerrSwampy on October 11, 2022, 12:46:53 PM
Hello, in my psychical chemistry lab we had done crysocopy exercise and i need to indentify chemical based on thesee informations:

molar mass: 45,21088 g/mol
white powder, easily made tablets with just pressure
Easily dissolves in water

Thanks for an help
Title: Re: Identifying unknown chemical
Post by: Babcock_Hall on October 11, 2022, 02:06:55 PM
What are your thoughts?
Title: Re: Identifying unknown chemical
Post by: HerrSwampy on October 11, 2022, 02:18:24 PM
It could have been MgO, but i am not sure at all
Title: Re: Identifying unknown chemical
Post by: mjc123 on October 11, 2022, 02:49:45 PM
If it was psychical chemistry, you should just know.
Title: Re: Identifying unknown chemical
Post by: HerrSwampy on October 11, 2022, 02:54:04 PM
Sadly it was cryoscopy, and they just gave us the chemical and told us to find its molar mass and try to think what chemical it is
Title: Re: Identifying unknown chemical
Post by: Borek on October 11, 2022, 03:28:47 PM
Quote from: HerrSwampy on October 11, 2022, 02:18:24 PM
It could have been MgO, but i am not sure at all

Would MgO easily dissolve in water?

Quote from: HerrSwampy on October 11, 2022, 12:46:53 PM
molar mass: 45,21088 g/mol

If it is your experimental value, it opens many more options. What is the heaviest element that the compound can contain? It is a compound, how many elements minimum does it contain? If so - what are possible molar masses of these element? Which elements fit? It is soluble - does it limit the selection of compounds? And so on.

Plus: often you are given a list of compounds to choose from.
Title: Re: Identifying unknown chemical
Post by: HerrSwampy on October 11, 2022, 03:30:29 PM
We were not given a list and yeah it was a experimental value of molar mass, so it could slightly different, I basicly need some idea that is closest to it
Title: Re: Identifying unknown chemical
Post by: Borek on October 11, 2022, 04:45:30 PM
Can't think of anything else than trial and error building on the ideas I listed - or finding on the web a database of compounds and searching it for compounds with similar molar mass.
Title: Re: Identifying unknown chemical
Post by: Orcio_87 on October 12, 2022, 09:46:45 AM
MgO would give an alkaline solution and its molar mass (40 g) differs from yours (45 g). There are other compounds that fit better - LiCl, Li2S and NaF.