Kevin Champagne
10/5/201
8
Period 5
Determination of Concentration by Oxidation-Reduction Titration
Purpose:
This experiment is designed to determine the concentration of hydrogen peroxide in a drugstore
bottle by titrating it with standardized KMnO
4
.
Pre-Lab Questions:
1.
In this experiment we are using a graduated cylinder and a buret to measure precise volumes.
Additionally, a flask is also useful for measuring precise volume.
2.
8H
+
+ MnO
4
-
+ 5e
-
→ Mn
2+
+ 4H
2
O (The Mn goes from a +7 charge to a +2 charge)
3.
H
2
O
2
→ O
2
+ 2H
+
+ 2e
-
(The oxygen goes from a -1 charge to a neutral charge)
4.
The two half reactions have a common multiple of 10e
-
, meaning that 10 mol e
-
are transferred in the
balanced redox reaction.
5.
Fe
+2
→ Fe
+3
+ e
-
6.
5e
-
+ 8H
+
+ MnO
4
-
→ Mn
2+
+ 4H
2
O (5 mol e
-
are transferred in this reaction)
7.
Perhaps copper could work, since it has both +2 and +3 oxidation states.
8.
We know that there is one MnO
4
-
ion in potassium permanganate, so the mol ratio is 1:1. Thus,
a.
x
mol MnO
4
-
/
0.0201 L = 0.020 M
b.
x =
0.0004 mol MnO
4
-
9.
