- The ferrous ion, Fe2+(aq), reacts with the permanganate ion, MnO 4 - _iaq, in an acidic
solution to produce the ferric ion, Fe3+(aq). A 6.893-gram sample of ore was
mechanically crushed and then treated with concentrated hydrochloric acid, which
oxidized all of the iron in the ore to the ferrous ion, Fe2+(aq). Next, the acid solution
containing all of the ferrous ions was titrated with 0.100 M KMnO 4 solution. The end
point was reached when 13.889 mL of the potassium permanganate solution was used.
(a) Write the oxidation half-reaction.
(b) Write the reduction half-reaction.
(c) Write the balanced final redox reaction.
(d) Identify the oxidizing agent, the reducing agent, the species oxidized, and the
species reduced.
(e) Calculate the number of moles of iron in the sample of ore.
(f) Calculate the mass percent of iron in the ore.Answer
- Given: Fe2+(aq) + MnO 4 - __aqii"Fe^3 + aq
6.893 grams of ore.
All of the iron in the ore was converted to Fe2+(aq).
Fe2+(aq)treated with 0.001 M KMnO 4 solution →Fe3+(aq).
13.889 mL of KMnO 4 required to reach end point.
(a) Restatement: Oxidation half-reaction.
Fe2+(aq)→Fe3+(aq) + e– OIL (Oxidation Is Losing)
(b) Restatement: Reduction half-reaction.
HO() 1
+++ 4()( ) argaq aq
aq aq aqaq aq aqMnO Mn balance O s
MnO H Mn H O balance H sMnO H e Mn H O balance ch e8485 41144
4(^22)
2
2
(^22)
"
"
"
- ++
++ +
++l
l__ ^___ ^
___ _ii hiii h
iii i(c) Restatement: Balanced redox reaction.
+++++ ++:
:ox Fe Fe e
red MnO H e Mn H O
MnO H Fe Mn H O Fe55
85 4
85 4554
423
2
2
22
2
3"
"
"+
++ +
++ ++
+Reduction and Oxidation