Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Claire_95 on December 09, 2011, 08:57:11 PM
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Okay, so there are 1.49 moles of Mg(NO3)2. There are 1.229*10E19 atoms of N in an unknown sample of Mg(NO3)2. How many miligrams will the sample weigh? I've tried everything I can think of, and I'm still stuck!
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OK, you have 3 different units in this question: moles, number of atoms, and grams. Do you know the relationship between the 3 so you can convert?
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Yes
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Numbers given (1.49 moles and 1.229x1019) are unrelated - they don't describe the same sample. Ignore 1.49, it is there just to confuse you.
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Sounds like you have 2 samples of Mg(NO3)2, but they are asking for the one with 1.229*10E19 atoms.
Use Avogadro's number to convert # of atoms to moles (because we all like working with small numbers instead of insanely large numbers).
1.229*10E19 atoms / Avogadro = number of moles of Mg(NO3)2
Then convert the # of moles to grams. Find the molar mass of Mg(NO3)2 which a simple search will provide or just calculate it yourself.