Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: noiseordinance on April 04, 2009, 01:50:59 PM
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Hey there. To start, I have really gotten the concept of moles / mass percent, etc. very well. I'm really stumped on a question however, and would really like some help figuring out the plan of attack. I don't want the answer, just the direction. Here's the question:
Hemoglobin, a protein in red blood cells, carries O2 from the lungs to the body's cells. Iron (as ferrous ion, Fe2+) makes up 0.33 mass % of hemoglobin. If the molar mass of hemoglobin is 6.8x104 g/mol, how many Fe2+ ions are in one molecule?
I've attacked this several ways and I'm just stuck. Can anyone offer some pointers?
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How many grams of iron per 1 mole of hemoglobin?
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Is there any other way you could express 0.33 mass %?
A tip: be explicit with your units... "g/mol" grams of what? moles of what?
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I originally came up with grams of iron per 1 mole of hemoglobin by taking (6.8x104 g/mol)(0.0033)=2.2x102 grams of iron... from there I'm totally lost. Do I use the mass percent to figure out empirical formula or something?
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Dear noiseordinance;
Now you have only one answer left to answer:
How many moles iron (Fe) are your 2.24 * 102 g iron?; and then you know how many mole Fe you have per mole HEM.
Good Luck!
ARGOS++
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Awesome. So is this one of those situations where I round? (My answer comes out to 4.01 Fe... dumb question but just making sure...)
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Yes.