redox titration question help!!Watch

#1
A 25.0cm3 aliquot of a solution containing Fe2+ ions and Fe3+ ions was acidified and titrated against potassium manganate(VII) solution. 15.0cm3 of 0.020M potassium manganate(VII) was needed. A second 25.0cm3 aliquot was reduced using zinc (i.e. the Fe3+ ions in the solution were reduced to Fe2+ ions), then titrated. This time, 19.0cm3 of the 0.020M potassium manganate(VII) was needed. Calculate the concentrations of:

a) Fe2+ ions in the solution b) Fe3+ ions in the solution

i am very confused someone help!
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3 years ago
#2
Sorry you've not had any responses about this. Are you sure you’ve posted in the right place? Posting in the specific Study Help forum should help get responses.

I'm going to quote in Puddles the Monkey now so she can move your thread to the right place if it's needed.

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3 years ago
#3
(Original post by ItsChrisG)
A 25.0cm3 aliquot of a solution containing Fe2+ ions and Fe3+ ions was acidified and titrated against potassium manganate(VII) solution. 15.0cm3 of 0.020M potassium manganate(VII) was needed. A second 25.0cm3 aliquot was reduced using zinc (i.e. the Fe3+ ions in the solution were reduced to Fe2+ ions), then titrated. This time, 19.0cm3 of the 0.020M potassium manganate(VII) was needed. Calculate the concentrations of:

a) Fe2+ ions in the solution b) Fe3+ ions in the solution

i am very confused someone help!
The first titration finds only the moles of the iron(II) ions.
The second titration finds the moles of both the iron(II) and the iron(III) ions (as all the iron(III) is previously reduced to iron(II)).

How do you think you find the moles of iron(III)?
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