October 29, 2020, 01:31:42 AM
Forum Rules: Read This Before Posting


Recent Posts

Pages: 1 [2] 3 4 ... 10
11
Undergraduate General Chemistry Forum / Re: Simple question
« Last post by chimias223 on Yesterday at 05:14:09 PM »
I think I need to multiply 75.23 with 7.4/100. but I'm not sure.

Idea is sound, but that's not what you did.
Yea I know. I think It's supposed to be the final soloution but I dont sure (5.567). can you help me with this,please?
12
Undergraduate General Chemistry Forum / Re: Simple question
« Last post by Borek on Yesterday at 05:04:59 PM »
I think I need to multiply 75.23 with 7.4/100. but I'm not sure.

Idea is sound, but that's not what you did.
13
Undergraduate General Chemistry Forum / Re: Simple question
« Last post by chimias223 on Yesterday at 04:58:44 PM »
Only 75.23 moles are OK

what's about the information ''Given that the relative prevalence of the 6-li isotope in nature is 7.4%''.?  should not use it?

I think I need to multiply 75.23 with 7.4/100. but I'm not sure.
14
Undergraduate General Chemistry Forum / Re: Simple question
« Last post by AWK on Yesterday at 04:29:37 PM »
Only 75.23 moles are OK
15
Citizen Chemist / Re: Extraction of caffeine from soda
« Last post by AWK on Yesterday at 04:06:46 PM »
Caffeine Free Mountain Dew also exists.
16
Citizen Chemist / Extraction of caffeine from soda
« Last post by zzbre1 on Yesterday at 03:50:25 PM »
Hello all!

Through Google, I’ve found this simple lab experiment for isolating the caffeine in a can of Mountain Dew:

http://chemistry.gravitywaves.com/rtf/CHE102/CHEM103L_Manual/Exp%208%20Caffeine.doc

My question is, if done correctly, would the resultant (now caffeine-free) Mountain Dew be safe to consume?

If not, is there a comparable procedure that would result in a safe-to-drink product?
17
Undergraduate General Chemistry Forum / Re: Simple question
« Last post by chimias223 on Yesterday at 02:26:46 PM »
You have to show your attempts or thoughts at solving the question to receive help.
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
http://www.chemicalforums.com/index.php?topic=65859.0

Sorry. This is waht I tried.
https://pasteboard.co/JxLUA6y.jpg
18
Organic Chemistry Forum for Graduate Students and Professionals / Re: Synthesis
« Last post by rolnor on Yesterday at 02:25:24 PM »
I think ypu can start with 4-cyano-1-bromobenzene and arylate a diimidazoline. Then you can hydrolyze the cyano groups with acid or base. This is a possible way to do it?
Or maybe fluoro-cyano-benzene is better, maybe you can buy this?
19
Hi, this is question pertaining accrediation of test methods.

I'm trying to validate TOC analysis according to ISO 8245:1999 (revised and approved in 2015). The water used for dilutions of samples and preparation of calibration standards is required to have maximum TOC levels which are about an order of magnitude or two below those intended for measurement (0,3 mg / L for measurement below 10 mg / L): trying to comply with this specification I run into a chicken-and-egg problem:

I can't use my typical calibration standards to confirm the absense of TOC in my dilution water since they have been prepared with that very water and in theory I can't use my calibration standards for measurement purposes since the dilution water is not verified.

Are there suppliers of water with purity specifications who satisfy these requirements? As far as I know low TOC water is supposed to be used as soon as it is prepared.

How do people comply with this requirement in practice?
20
Undergraduate General Chemistry Forum / Re: Simple question
« Last post by billnotgatez on Yesterday at 02:10:58 PM »
You have to show your attempts or thoughts at solving the question to receive help.
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
http://www.chemicalforums.com/index.php?topic=65859.0
Pages: 1 [2] 3 4 ... 10