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What mass of the compound CrO3 (M = 100.0) contains  4.5x10^23 oxygen atoms?

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lak-86 | Student, Undergraduate | Salutatorian

Posted June 12, 2013 at 12:40 PM via web

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What mass of the compound CrO3 (M = 100.0) contains 
4.5x10^23 oxygen atoms?

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted June 12, 2013 at 12:50 PM (Answer #1)

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According to Avogadro 1 mol of a substance contains `6.022xx10^23` atoms.

Here we have `4.5xx10^23` atoms of oxygen.

Mole ratio

`CrO_3:O = 1:3`

 

So we have `(4.5xx10^23)/3` atoms of `CrO_3` in the compound.

 

Amount of `CrO_3` moles

`= [(4.5xx10^23)/3]/(6.022xx10^23)`

`= 0.25`

 

So we have 0.25 moles of `CrO_3` in `4.5xx10^23` atoms of Oxygen in `CrO_3` .

 

Mass of `CrO_3 = 0.25molxx100g/(mol) = 25g`

 

So we need 25g of `CrO_3` .

 

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