# CHEM 11

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I am really stuck with this...
what mass of oxygen is contained in 10.5 umol of chromium(III)nitrate hexahydrate?

Can't understand how to convert the micro-moles especially!

• CHEM 11 -

Cr(NO3)3.6H2O.
mass = moles x molar mass
You know molar mass, so all you really need to know is # moles.
10.5 umol Cr(NO3)3.6H2O = 10.5E-6 mole for a mole of Cr(NO3)3.6H2O. Now how many moles O are in 1 mole Cr(NO3)3.6H2O. I see 9 so multiply 10.5E-6 mol x 9 to convert to moles oxygen, then moles x 16 (since I counted O atoms).Check my work. My eyes are getting bleary.

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