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Ex 4 Vanadium - Lab report 4
General Chemistry Laboratory I (Yale University)
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Gathecha
1
Chemistry 134L Laboratory Report
4. Oxidation States of Vanadium
Purposes of the experiment and brief overview of the experimental methods
The first purpose of this experiment was to observe the TA’s demonstration in order to study the color
changes that occur when the oxidation state of an element is changed using two different indicators
(Congo Red and thymolphthalein). This was done by watching the TA use sulfuric acid, potassium
iodide, starch, ascorbic acid, NaOH pellets, the previously mentioned indicators, and water to carry out
various oxidation and reduction reactions in both acidic and basic conditions.
The second purpose of this experiment was to study and observe the various oxidation states of the
element vanadium. This was done using a vanadium stock solution (where vanadium existed in the 5+
oxidation state as VO ), and the reducing agents zinc metal and sodium thiosulfate. First, a reduction
2
+
using sodium thiosulfate was carried out, the product of which was titrated with potassium
permanganate to determine the molar ratio between the vanadium of unknown oxidation state and
permanganate ion, to determine the oxidation state of vanadium before the titration. Similarly, two
reductions of vanadium by zinc were carried out using different volumes of vanadium stock solution.
In this part of the experiment (parts II and III), comproportionation was utilized to oxidize the reduced
solutions into a stable state, which was then titrated with potassium permanganate to determine the
molar ratio between the vanadium of unknown oxidation state and permanganate ion, which could be
used to determine the oxidation state of vanadium before the titration.
Results (be careful with significant figures throughout; show units)
Molarity of VO2+ solution used: 0.0500 M Molarity of KMnO4 used: 0.040 M
Downloaded by john gatheca ()
Gathecha
Ex 4 Vanadium - Lab report 4
General Chemistry Laboratory I (Yale University)
Studocu is not sponsored or endorsed by any college or university
Downloaded by john gatheca ()
, lOMoARcPSD|28964921
Gathecha
1
Chemistry 134L Laboratory Report
4. Oxidation States of Vanadium
Purposes of the experiment and brief overview of the experimental methods
The first purpose of this experiment was to observe the TA’s demonstration in order to study the color
changes that occur when the oxidation state of an element is changed using two different indicators
(Congo Red and thymolphthalein). This was done by watching the TA use sulfuric acid, potassium
iodide, starch, ascorbic acid, NaOH pellets, the previously mentioned indicators, and water to carry out
various oxidation and reduction reactions in both acidic and basic conditions.
The second purpose of this experiment was to study and observe the various oxidation states of the
element vanadium. This was done using a vanadium stock solution (where vanadium existed in the 5+
oxidation state as VO ), and the reducing agents zinc metal and sodium thiosulfate. First, a reduction
2
+
using sodium thiosulfate was carried out, the product of which was titrated with potassium
permanganate to determine the molar ratio between the vanadium of unknown oxidation state and
permanganate ion, to determine the oxidation state of vanadium before the titration. Similarly, two
reductions of vanadium by zinc were carried out using different volumes of vanadium stock solution.
In this part of the experiment (parts II and III), comproportionation was utilized to oxidize the reduced
solutions into a stable state, which was then titrated with potassium permanganate to determine the
molar ratio between the vanadium of unknown oxidation state and permanganate ion, which could be
used to determine the oxidation state of vanadium before the titration.
Results (be careful with significant figures throughout; show units)
Molarity of VO2+ solution used: 0.0500 M Molarity of KMnO4 used: 0.040 M
Downloaded by john gatheca ()
