Experiment 10

EXPERIMENT 10

POTENTIOMETRIC
REDOX TITRATION

BAUTISTA ,
Anne Judith
LARIN,
Michelle V.

OBJECTIVES

At the end of the experiment, the student should be able to:
1.Construct a potentiometric redox titration curve
2.Determine the % Fe in a sample by potentiometric redox titration

INTRODUCTION

Potentiometry
definition
indicator electrode
reference electrode
Potentiometric titration
applications
general procedure
similarities with redox titration

INTRODUCTION
Determining the endpoint from a potentiometric redox titration curve:

EXPERIMENTAL

Preparation of Cu/Cu2+ Reference Electrodes

5 cm Pasteur pipet: plugged

with cotton  saturated KCl/KNO3,
0.1 M of CuSO4 solution

Copper wire voltmeter
Modelling clay

EXPERIMENTAL

Preparation of KMnO4

weight of KMnO4 = ?
300 mL of 0.01 M solution
Dissolve in 100 mL distilled water.
Dilute to reach 300 mL.

Store in a colored container.

EXPERIMENTAL

Standardization of KMnO4
0.3 g-0.4 g of Fe(NH4)2(SO4)2●6H2O
•100 mL beaker: 20 mL distilled water, 5 mL 2M H2SO4  voltmeter
2 mL increments of KMnO4 (Vtotal = 20 mL)
1 mL increments of KMnO4 (Vtotal = 30 mL)

Measure reduction potentials.
Repeat to make 3 trials.

EXPERIMENTAL

Standardization of KMnO4
10 mL unknown  diluted: 100 mL
10 mL (diluted) + 5 mL of 2M H2SO4
2 mL increments of KMnO4 (Vtotal = 20 mL)
1 mL increments of KMnO4 (Vtotal = 30 mL)

Measure reduction potentials.
Repeat to make 3 trials.

RESULTS: TRIAL 1

RESULTS: TRIAL 1

RESULTS: TRIAL 1

RESULTS: TRIAL 1

RESULTS: TRIAL 2

RESULTS: TRIAL 2

RESULTS: TRIAL 2

RESULTS: TRIAL 2

RESULTS: TRIAL 3

RESULTS: TRIAL 3

RESULTS: TRIAL 3

RESULTS: TRIAL 3

DISCUSSION

Reference electrode, Eref
Salt bridge, Ej
Analyte solution and Indicator electrode, Eind

DISCUSSION

DISCUSSION

DISCUSSION

DISCUSSION

RECOMMENDATIONS

Voltmeter
CuSO4 solution
KMnO4