Stoichiometry Grams to Grams

Question

2 Fe₂O₃ + 3C —> 4 Fe + 3CO₂

1) How many grams of Fe will be produced if 39.64 grams of CO₂ are used ?

2) How many grams of FeO₂ are used if 2.88 grams of Fe are produced ?

Answer 1

I don't think you mean the 39.64 g of CO₂ are used, but rather they are produced.

Also, these are not Grams to Grams calculations. These are GRAMS to MOLES to GRAMS calculations.

2 Fe₂O₃ + 3C —> 4 Fe + 3CO₂

mol ratio of Fe produced to CO₂ produced is 4 : 3

moles CO₂ produced = 39.64 g CO₂ x 1 mol CO₂/44.01 g = 0.9007 moles CO₂

mass Fe = 0.9007 mol CO₂ x 4 mol Fe/3 mol CO₂ x 55.85 g Fe/mol Fe = 67.07 g Fe produced

Here, I think you mean how many grams of Fe₂O₃ are used, not grams of FeO₂.

The mole ratio of Fe produced to Fe₂O₃ used is 4 : 2 or 1 : 2

2.88 g Fe x 1 mol Fe/55.85 g x 2 mol Fe₂O₃ / 4 mol Fe x 159.69 g Fe₂O₃/mol Fe₂O₃ = 4.12 g Fe₂O₃ used

Answer 2

First a couple of observations.

CO₂ is produced not used.

FeO2 is not part of the equation but we will make the assumption you meant Fe₂O₃

Convert grams to moles by dividing grams by the Gram Molecular Mass

For CO₂ that is 39.64/ 44.01 this gives us 0.9007 moles.

For Fe that is 2.88/55.85 this gives us 0.052 moles

1. Since the molar ratio of Fe to CO₂ is 4/3 then multiply the moles produced of CO₂ by 4/3 to obtain the moles of Fe produced. This value is 1.201 moles.

Convert moles to grams by multiplying by the Gram Molecular Mass of Fe which is 55.85 and you will get the number of grams of Fe produced. This value is 67.08 g

2 Repeat the process used in number 1 above only this time using the values for Fe

Since 0.052 moles of Fe are produced and since the molar ratio between Fe₂O₃ and Fe is 2/4 (or 1/2) then multiply 0.052 by 2/4 and you will have the number of moles of Fe₂O₃ that were used. This value is 0.026 moles

Multiply the number of moles of Fe₂O₃ used by the Gram Molecular Mass of Fe₂O₃ which is 159.70

This will give you the number of grams of Fe₂O₃ The answer is 4.15 grams