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Topic: Elemental Composition and Compund Stoichiometry  (Read 12135 times)

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sundrops

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Elemental Composition and Compund Stoichiometry
« on: January 21, 2005, 02:04:37 AM »
The green pigment chlorophyll a, absorbs red light, the energy from which powers photosynthetis processes in plants and algae.

Chlorophyll a is 6.27% nitrogen by mass.
Each molecule of chlorophyll a contains 4 nitrogen atoms.

What is the molecular mass of chlorophyll a?

I'm really confused, I don't even know how tio attack this question - I mean I don't know what chlorophyll is made up of - it doesn't seem like there's enough info. Please *delete me*

Offline Mitch

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Re:Elemental Composition and Compund Stoichiometry
« Reply #1 on: January 21, 2005, 02:38:15 AM »
What is the mass of 4 Nitrogens?
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sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #2 on: January 21, 2005, 02:45:12 AM »
mass of 4 nitrogens would be 14.01 * 4 = 56.04g
right? but how does that help me?

Offline Mitch

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Re:Elemental Composition and Compund Stoichiometry
« Reply #3 on: January 21, 2005, 02:52:18 AM »
That was the mass of 6.27% of the molecule.
What is the mass of the other 93.73% of the molecule? Then calculate the total mass for 1 molecule.
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sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #4 on: January 21, 2005, 03:00:11 AM »
OH! that makes sense! but the mass of the rest of the rest of the molecule isn't given! thats what makes this question sooo hard! not enough information. its frusterating!!

sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #5 on: January 21, 2005, 03:34:19 AM »
how do i find the mass of the other 93.73% of the molecule?

Offline AWK

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Re:Elemental Composition and Compund Stoichiometry
« Reply #6 on: January 21, 2005, 06:55:42 AM »
6.27/56.04 = 100/x
where x is the molecular mass of chlorophyl
« Last Edit: January 21, 2005, 08:13:58 AM by AWK »
AWK

sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #7 on: January 21, 2005, 10:18:07 AM »
oh - that makes sense  :D
thanks so much!

sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #8 on: January 21, 2005, 02:42:01 PM »
now what if the chlorophyll molecule contains 1 magnesium atom.
what mass of magnesium is to be found in 2.97 g of chlorophyll?

sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #9 on: January 21, 2005, 03:10:22 PM »
how would i go about trying to solve that?

Offline Mitch

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Re:Elemental Composition and Compund Stoichiometry
« Reply #10 on: January 21, 2005, 03:47:56 PM »
It wouldn't matter.
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sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #11 on: January 21, 2005, 05:00:55 PM »
but that's part II of the question - i need to figure it out somehow. I need to find out how much magnesium is in 2.97 g of chlorophyll - how would i go about doing that?

dexangeles

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Re:Elemental Composition and Compund Stoichiometry
« Reply #12 on: January 21, 2005, 05:36:15 PM »
you already have the total mass of chlorophyl, so the mass of 1 magnesium atom is what percent of that total mass?

start from there  ;)

sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #13 on: January 22, 2005, 05:37:17 AM »
ok so if percent nitrogen is 6.27% and the mass of nitrrogen is 56.04g

then with the mass of 1 magnesium atom being 24.31g - then it's percentage of the total mass would be 2.72% !! ;D

that makes sense!


sundrops

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Re:Elemental Composition and Compund Stoichiometry
« Reply #14 on: January 22, 2005, 05:39:24 AM »
now, how would I apply that information into determinig how much magnesium I would find in 2.97g of chlorophyll?  :-\

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