1.

A quantity of 25.0 mL of solution containing both Fe^(2+) and Fe^(3+) ions is titrated with 25.0 mL of 0.0200 M KMnO_(4) (in dilute H_(2)SO_(4)). As a result, all of the Fe^(2+) ions are oxidised to Fe^(3+) ions. Next 25 mL of the original solution is treated with Zn metal finally, the solution requires 40.0 mL of the same KMnO_(4) solution for oxidation to Fe^(3+). MnO_(4)^(-)+5Fe^(2+)+8H^(+)toMn^(2+)+5Fe^(3+)+4H_(2)O IF 0.02 M K_(2)Cr_(2)O_(7) is used instead of 0.02 M KMnO_(4) its volume required in these titrations are respectively

Answer»

25 mL, 40 mL
25 mL, 15 mL
20.8 mL, 33.3 mL
10.4 mL, 16.7 mL

Solution :m.eqts of `Fe^(+2)` = mEq.ts of `KMnO_(4)`
implies m. Eq.ts of `Fe^(+2)=25xx0.02xx5=2.5`
In PRESSURE of Zn,
m.eqts of `Fe^(+3)` = m eqts of `KMnO_(4)`
implies m. Eq.ts of `Fe^(+2)=25xx0.02xx5=2.5`
In pressure of Zn,
me.eqtsof `Fe^(+3)` = m eqts of `KMnO_(4)`
m.eqts of `Fe^(+3)` = m eqts of `KMnO_(4)`
m.eqts of `Fe^(+3)=40xx0.02xx5=4`
Now in the second case `K_(2)Cr_(2)O_(7)`
used instead of `KMnO_(4)`,
m eq. `K_(2)Cr_(2)O_(7)` =m eq of `Fe^(+2)`
`0.02xx6xxv=2.5`
`implies V=(2.5)/(0.12)=20.8ml`
In pressure of Zn
m. eqts of `K_(2)Cr_(2)O_(7)` = m eq of `Fe^(+3)`
`0.02xx6xxv=2`
`impliesV=(4)/(0.12)=33.3ml`


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