Experiment: Oxidation States of Manganese
Name:_______________________________________
Period_____________
Purpose: To prepare solutions of manganese ions in different oxidation states and predict the identity of compounds..
Materials
White ceramic Spot Plate
KMnO4 solution
2.0 mol/L NaOH(aq)
NaHSO3 solution
stirring rod
3.0 mol/L H2SO4(aq)
0.1 mol/L EDTA solution
MnSO4 solid (a pinch)
Pre-Lab activity: Determine the oxidation number of Mn in each of the following compounds of manganese.
Compound
Oxidation number of Mn
Colour
MnSO4 (aq)
MnCl3 (aq)
COLOURLESS
VIOLET/ROSE
MnO2 (s)
BROWN
K2MnO4 (aq)
GREEN
KMnO4 (aq)
PURPLE
Procedure
1. Label 4 spot plate depressions A, B, C and D. Place about 10 drops of potassium permanganate
solution (KMnO4) in each spot. Place 10 drops of the remaining KMnO4 in well E.
2. Add 3 drops of 3.0 mol/L H2SO4(aq) to spot A
3. Add 4 drops 2.0 mol/L NaOH(aq) to spot B.
4. Slowly add a drops of NaHSO3(aq) while stirring to A (5-10 drops) B (10-20 drops) and C (5
drops ). Note the changes which take place and record you observations.
5. Add 10 drops of 0.1 mol/L EDTA solution and a pinch of solid manganese sulfate to spot D.
Stir and record your observations.
6. Arrange the five beakers to show the colours of the Mn ions in their various oxidation states.
7. Use your pre-lab activity to identify the manganese ions present in spots A,B, C, D and E. Record in the
observation table.
Observations: Title____________________________________________________
Spot
A
B
C
D
E
Observed Colour
Oxidation state for
Mn
Mn compound in
product
Analysis:
1. List all of the chemical entities added to well A. Dissociate compounds as needed and consider that the acid
environment will add a proton to hydrogen sulphite ion. Use the Redox chart to label the entities as OA or RA,
choose the strongest and write the balanced chemical equation.
2. List all of the chemical entities added to well B. Dissociate compounds as needed and consider that the basic
environment will remove a proton from hydrogen sulphite ion. Use the Redox chart to label the entities as OA or
RA, choose the strongest and write the balanced chemical equation.
3. Do the products in your observations match the products in your above reactions? Suggest 5 sources of error or
limitations to the experiment.
4. Why was well E used?
5.