M19

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705088777
Posts: 37
Joined: Fri Sep 28, 2018 12:18 am

M19

Postby 705088777 » Mon Oct 08, 2018 6:00 pm

how are we supposed to determine the molecular formula of caffeine without looking it up?

Maria Solis Disc 1G
Posts: 63
Joined: Fri Sep 28, 2018 12:27 am
Been upvoted: 2 times

Re: M19

Postby Maria Solis Disc 1G » Mon Oct 08, 2018 6:05 pm

If you're talking about the homework problem it should give you the molar mass of caffeine, and the percent composition. so you would multiply each percentage by the total molar mass. I don't think we should be expected to know the formula for caffeine, considering it's so early in the year.

Fanny Lee 2K
Posts: 73
Joined: Fri Sep 28, 2018 12:29 am

Re: M19

Postby Fanny Lee 2K » Mon Oct 08, 2018 6:41 pm

The professor said that anything on the test relating to naming compounds are given to you. However once we learn about the composition of the molecules and the names associated with it, then we are expected to know the formula.

Leela_Mohan3L
Posts: 44
Joined: Fri Sep 28, 2018 12:26 am

Re: M19

Postby Leela_Mohan3L » Mon Oct 08, 2018 8:40 pm

In this problem, you can determine the molecular formula of caffeine by finding the grams of Carbon, Hydrogen, and Nitrogen that are present. Once you add these masses up, you'll see that they do not equal the total mass of the initial hydrogen compound and therefore there has to be another element present in caffeine--oxygen. You would then go about the normal way of finding a molecular formula.

Hope that helps!


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