DAT Achiever Chem Question

[Carrie22]

What mass of chromium is theoretically obtainable from 1.00 kg of ore containing 76% of Cr2O3?


A. 26g
B. 52g
C. 260g
D. 520g
E. 600g

I did this:
(.76)(1000g ore)(1 mole ore/152g ore)(5mol Cr2O3/1mol ore)(2 mol Cr2/1mol Cr2O3)(104g Cr2/1mol Cr2)
What is wrong with this setup?? when they ask for the mass of chromium is does that mean only Cr not Cr2 right? help I'm freaking out!

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[building]

What mass of chromium is theoretically obtainable from 1.00 kg of ore containing 76% of Cr2O3?


A. 26g
B. 52g
C. 260g
D. 520g
E. 600g

I did this:
(.76)(1000g ore)(1 mole ore/152g ore)(5mol Cr2O3/1mol ore)(2 mol Cr2/1mol Cr2O3)(104g Cr2/1mol Cr2)
What is wrong with this setup?? when they ask for the mass of chromium is does that mean only Cr not Cr2 right? help I'm freaking out!

haha relax.

it's just 76 percent of the mass is composed of Cr2O3

so figure out the percent of Cr in Cr2O3

(52+52)/(52+52+16+16+16) ~ .684

take that multiple by the weight of the Cr2O3

.684 x 1000g x .76 = 520g of Cr

tada!

 

[Carrie22]

oh thanx your explanation is more clear than the authors of achiever