Experiment 15:

The Determination of Iron(II)
by Redox Titration

 

 

 

Overview 

 

 

 

 

5 X (Fe2+  Fe3+ + e-)          oxidation

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

___________________________________________________________________________

MnO4- + 5Fe2+ + 8H+   Mn2+ + 5Fe3+ + 4H2O          overall process

 

 

 

Data 

 

 

       

 

Before Transfer

After Transfer

Mass of Sample

Sample 1

15.1249 g

14.1157 g

1.0092 g

Sample 2

14.1157 g

13.0979 g

1.0178 g

Sample 3

13.0979 g

12.0052 g

1.0927 g

       

 

 

       

 

Initial

Final

Vol. of KMnO4

Sample 1

0.25 mL

25.36 mL

25.11 mL

Sample 2

1.24 mL

26.58 mL

25.34 mL

Sample 3

1.09 mL

28.30 mL

27.21 mL

       

 

 

       

 

Before Transfer

After Transfer

Mass of Sample

Unknown Sample 1

35.2453 g

34.0101 g

1.2352 g

Unknown Sample 2

34.0101 g

32.7524 g

1.2577 g

Unknown Sample 3

32.7524 g

31.5031 g

1.2493 g

       

 

 

       

 

Initial

Final

Vol. of KMnO4

Sample 1

0.29 mL

26.30 mL

26.01 mL

Sample 2

1.04 mL

27.51 mL

26.47 mL

Sample 3

2.10 mL

28.40 mL

26.30 mL

       

 

 

Calculations 

 

 

    1. The balanced equation is given in the Overview above. You will have to show how the half reactions are combined to give this on your lab report.
    2. The factor is five

    Page 160, Part II B

    1. Moles of ferrous ammonium sulfate hexahydrate in Sample 1

    The number of moles of anything is calculated from the mass of sample and the molar mass. The molar mass of Fe(NH4)2(SO4)2.6H2O is 392.2 g. For sample 1, in which the mas of FAS taken was 1.0092 g, calculate the number of moles of FAS present, then click here to check your answer.

 


 

 


 

 

 

     

Results

Molarity of KMnO4

Deviation

Sample 1

0.02049 M

0.00001 M

Sample 2

0.02048 M

0.00000 M

Sample 3

0.02047 M

-0.00001 M

Average

0.02048 M

0.0000067 M 0.00001 M

     

 

 

 

 

 

 

 

 

 

 

 

 

 

        4. %Fe by Mass in Unknown Sample 1

 

 

 

 

 

        5. Summary of Results

 

         
 

moles Fe2+

grams Fe

%Fe

Deviation

Unknown 1

0.002634 moles

0.1488 g Fe

12.05% Fe

0.01

Unknown 2

0.002711 moles

0.1514 g Fe

12.04% Fe

0.00

Unknown 3

0.002693 moles

0.1504 g Fe

12.04% Fe

0.00

   

Average

12.04% Fe

0.003%

         

 

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