[fchs]

If from a 50.0g sample of an iron ore containing Fe3O4, 2.09g of Fe is obtained by the  (unbalanced) reaction:
   Fe3O4  +  C ---->  Fe  +   CO2 

What is the percent of Fe3O4 in the iron ore?

50.g Fe3O4 x mol Fe3O4  x   3 mol Fe    x  55.85g Fe
                       --------------     -------------    ------------- = 36.18g Fe
                  231.55g Fe3O4    mol Fe3O4       mol Fe
% yield = experimental                 2.09
                ----------------x 100 =  ----------- x 100= 5.78%
                   theatrical                     36.18


Is this correct? I'm concerned because the percentage seems small. It asks for Fe3O4, but gives that 2.09g of Fe is obtained not Fe3O4.


Thanks

[Bakegaku]

I may have misinterpreted it, but if you copied your question directly as it was from the book I don't think it's asking for percent yield. 

What is the percent of Fe3O4 in the iron ore?

I believe you're supposed to answer this question by using the fact that 2.09g of Fe₃O₄ was obtained from the ore.  The wording of "an iron ore containing Fe₃O₄" implies impurity, as well.

[fchs]

I may have misinterpreted it, but if you copied your question directly as it was from the book I don't think it's asking for percent yield. 

What is the percent of Fe3O4 in the iron ore?

I believe you're supposed to answer this question by using the fact that 2.09g of Fe₃O₄ was obtained from the ore.  The wording of "an iron ore containing Fe₃O₄" implies impurity, as well.

so is it

2.09g Fe = 1 mol Fe x Fe3O4 x 231.55 g Fe3O4
               55.85g Fe  3 mol Fe mol Fe3O4              = 2.88g

2.88/50. x 100= 5.76%?


We haven't really touched this subject much, but she's gives us these problems ahead of time hoping we'll get it..please help lead me on the right track

[Bakegaku]

Well I used my computer calculator, and I actually got your original answer   

For the first part I got 2.888.... which would be rounded to 2.89 for sig figs. 

I guess in this case you did a similar operation, but hopefully you'll catch something like that in a question where the answer doens't come out the same. 

[fchs]

Well I used my computer calculator, and I actually got your original answer   

For the first part I got 2.888.... which would be rounded to 2.89 for sig figs. 

I guess in this case you did a similar operation, but hopefully you'll catch something like that in a question where the answer doens't come out the same. 

so would I then take 2.89g/50.g x 100?

[Bakegaku]

Well I used my computer calculator, and I actually got your original answer   

For the first part I got 2.888.... which would be rounded to 2.89 for sig figs. 

I guess in this case you did a similar operation, but hopefully you'll catch something like that in a question where the answer doens't come out the same. 

so would I then take 2.89g/50.g x 100?

Yeah.  As I said it comes out to the same number.