gchem Q#60 from Achiever Test2 ???

[Dentista08]

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If 1 kg sample of ore contains 76% of Cr2O3 what mass of Cr is theoretically obtained from the ore?
They give the explanation below, if 5 moles that they come up with are moles of Cr2O3 in the ore, then why do we multiply (5)(2)(52g of Cr) to get 520 g of Cr??

.76(1000)/((2x52)+(3x16) )=5


Since each mole of Cr2O3 contains 2 moles of Cr, the theoretical mass of Cr obtainable is therefore:
2x5x52=520g

Thanks in advance!

 

[Daydream46]

If 1 kg sample of ore contains 76% of Cr2O3 what mass of Cr is theoretically obtained from the ore?
They give the explanation below, if 5 moles that they come up with are moles of Cr2O3 in the ore, then why do we multiply (5)(2)(52g of Cr) to get 520 g of Cr??

.76(1000)/((2x52)+(3x16) )=5


Since each mole of Cr2O3 contains 2 moles of Cr, the theoretical mass of Cr obtainable is therefore:
2x5x52=520g

Thanks in advance!

Im not looking at the problem, but im guessing:
5 moles Cr2O3 x 2 Cr per mol of Cr203 x 52 grams per Cr

if thats what your asking... if not sorry

 

[MattEvers]

I'd just use what they gave you and add true statements until you get the answer... you'll never go wrong this way. It's the way my professor taught us.

176 g Cr2O3 x 1 mol Cr203/152 g Cr2O3 x 2 moles Cr/1 mol Cr2O3 x 52 g Cr/1 mol = 520 g

The g of Cr2O3 cancel out in the first statement leaving moles of Cr2O3. Then moles of Cr2O3 are canceled out with moles of CR left. Then moles of Cr are canceled to get g of Cr.

 

[Dentista08]

thanks!!! totally helps 👍