Chemistry Problem!

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What weight of sample containing 8.00 % Fe3O4 must be taken to obtain a precipitate of Fe(OH)3 that, when ignited to Fe2O3, weighs 150 mg?

  • Chemistry Problem! -

    Work it backwards.
    You want to end up with 150 mg Fe2O3. How much Fe(OH)3 must you have?
    150 mg Fe2O3 x [2*molar mass Fe(OH)3/molar mass Fe2O3] = ? mg Fe(OH)3
    What must be the mass Fe3O4?
    ?mg Fe(OH)3 x [2*molar mass Fe3O4/3*molar mass Fe2O3] = ? mg Fe3O4.
    Since that mg Fe3O4 is only 8%, then
    mass sample x 0.08 = ?mg Fe3O4 and solve for mass sample.
    Those factors I used come from this.
    2Fe3O4 ==> 3Fe2O3
    Fe2O3 ==> 2Fe(OH)3
    I didn't balance the oxygen atoms since we are working only with the Fe

    Check my work.

  • Chemistry Problem! -

    Thanks a lot

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