Chemistry / mass stiochemistry question

Question

Antimony can be prepared from sulfide ore by the following two-step process. What mass of antimony will be produced if 1.00 kg of ore that contains 23.2% of Sb2S3 by mass is reacted with excess of oxegon? 

 

2sb2S3 +902 -> Sb4O6 + 6SO2

 

Sb4O6 + 6C -> 4Sb + 6Co 

 

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Answer 1

So, this is a problem of recognizing stoichiometric relationships between reactants and products, and of mass to mole conversions.  Essentially, you are given (or can calculate) the mass of Sb₂S₃ that you begin with, and are asked to find the mass of Sb produced as a final product.  Since O₂ is in excess, there is no need in this problem to find the limiting reactant.  Also, you are already given the balanced equations, so no need to balance them.  Let's begin.

 

1.00 kg ore x 0.232 = 0.232 kg of Sb₂S₃ as starting mass (corrected for 23%)

Finding moles Sb₂S₃: 

0.232 kg Sb₂S₃ x 1000 g/kg x 1 mole/339.7 g = 0.683 moles Sb₂S₃

 

Finding moles Sb₄O₆ produced:

0.683 moles Sb₂S₃ x 1 mole Sb₄O₆/2 moles Sb₂O₃ = 0.342 moles Sb₄O₆

 

Find moles of Sb produced:

0.342 moles Sb₄O₆ x 4 moles Sb/1 moles Sb₄O₆ = 1.37 moles Sb

 

Find mass of Sb produced:

1.37 moles Sb x 121.8 g/ mole = 167 g Sb produced