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leelo leelo
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10 years ago
I have 2',7'-dichlorofluoroscein with a MW of 401.20. I need to make a 150 uM stock solution with a final volume of 50 ml. How many grams of the compound should I weigh out?

I have to do a few things like this in lab and I am getting confused when the molarity is in uM and nM. Can you explain exactly how you got your answer? I have one but I'm not sure if I did it correctly.
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ff.marquisff.marquis
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10 years ago
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fey
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10 years ago
The key is to use the units of each measurement to help you with your solution and to keep the units consistent throughout your stoichiometric equation.  For example, instead of writing your equation out with 50 mL to start, write its as 0.050 L; 150 uM can instead be 0.000150 mol/L.  You then just need to put everything together so that all the units cancel out except for grams.  Here's how I would write it:

(0.050 L) * [(0.000150 mol) / (1 L)] * [(401.20 g) / (1 mol)] = 0.0030 g or 3.0 mg
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