Not logged in [Login - Register]
 Sciencemadness Discussion Board » Fundamentals » Beginnings » Molecular Weight Determination Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication   » References Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Whimsy   » Detritus   » The Moderators' Lounge

Author: Subject: Molecular Weight Determination
RedsAreRaw
Harmless

Posts: 7
Registered: 30-12-2016
Member Is Offline

Mood: No Mood

Molecular Weight Determination

Ran across a question when working through my Morrison and Boyd Organic book that went: The hormone insulin contains 3.4% sulfur. (a) What is the minimum molecular weight of insulin? (b) The actual molecular weight is 5734; how many sulfur atoms are probably present per molecule?

I honestly just took a stab in the dark by dividing 3.4/32.06 to get about 10% and divided this into the remaining 96.6% to get a ratio of about 1 to 10 for C,H, and O. So I just guess C10H10O10S to get an answer of 322.23 for (a). and then divided that into 5734 to get 18 for S.

The answer was actually 942 for (a) and 6 for (b).

How do you go about solving this question?

Thanks
Texium (zts16)
Super Moderator
6-1-2017 at 09:23
Texium (zts16)
Super Moderator

Posts: 2736
Registered: 11-1-2014
Location: San Marcos, TX
Member Is Offline

Mood: Hoarding bottles like a person who hoards bottles

First you do 32.06/.034 which gives you 942. That would be if 1 molecule of sulfur represented 3.4% of the mass of the molecule.

Then you simply divide 5734 by 942 to get about 6. Or you can get the same answer by doing 5734 x .034, and then that answer /32.06, to give approximately 6.

aga
Forum Drunkard

Posts: 6862
Registered: 25-3-2014
Member Is Offline

Mood: Para/Dia-letic

If it's any consolation, i stared at that for a while, and was a bit lost.

Overthinking things tends to be a recurring problem.

Now the problem has been worked through, it seems so obvious.

Thanks zts16 !

Madness is thinking i'm not drunk.
RedsAreRaw
Harmless

Posts: 7
Registered: 30-12-2016
Member Is Offline

Mood: No Mood

 Quote: Originally posted by aga Now the problem has been worked through, it seems so obvious.

That's exactly what I thought as well.

Thanks zts16 for the quick reply!

 Sciencemadness Discussion Board » Fundamentals » Beginnings » Molecular Weight Determination Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication   » References Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Whimsy   » Detritus   » The Moderators' Lounge