Question

1. Re-write the iron-permanganate reaction and indicate: a. the oxidizing agent, b. reducing agent, c. the species that gets oxidized, and d. the species that gets reduced.

2. An acidic solution of permanganate ion reacts with oxalate (C2O4) ion to form carbon dioxide and Mn (II). Write a balanced equation for the reaction.

3. Referring to the reaction in question 2, 38.4 mL of 0.150M KMnO4 solution is required to titrate the 25.2 mL of a sodium oxalate solution. What is the concentration of oxalate ion in the solution?

4. Suggest an alternative way to determine Fe quantitatively.

Answer 1

1.

iron(II) cations, Fe²⁺, are oxidised to iron(III) cations,Fe³⁺

MnO₄^-, is reduced to manganese(II) cations, Mn²⁺

MnO₄^-   is the oxidising agent

Fe²⁺ is the reducing agent

2

MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O

C2O4(2-) -> 2CO2 + 2e-

Overall

2MnO4- + 5C2O4(2-) + 16H+ -> 2Mn2+ 10CO2 + 2Mn2+ + 8H2O

3.

38.4*0.150=25.2*C

C=0.229 M

4.

Find moles of KMnO4:
0.03840 litres @ 0.150 mol / litre = 0.00576 moles KMnO4 (first answer)
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using the equation:
MnO4^- + 5 Fe^2+ 8H^+ --> Mn^2+ 5 Fe^3+ 4H2O
find moles of Fe:
0.00576 moles KMnO4 @ 5 mol Fe / 1 mol KMnO4 =
0.0288 moles of Fe (second answer)
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find grams of Fe , using its molar mass:
0.0288 moles of Fe @ 55.85 g/mol =
1.608 grams of Fe

find % Fe:
(1.608 grams of Fe / no of g sample of iron ) times 100= required iron percentage