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Questions and Answers
RPME can be used at positive potential up to + ______ Volt.
RPME can be used at positive potential up to + ______ Volt.
0.9
The diffusion current of RPME is ______ times larger than DME.
The diffusion current of RPME is ______ times larger than DME.
20
Amperometric titration can determine both reducible and non-reducible ______.
Amperometric titration can determine both reducible and non-reducible ______.
ions
The endpoint in Karl Fischer titration is detected when the current is ______.
The endpoint in Karl Fischer titration is detected when the current is ______.
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Amperometric titration can be used to determine the concentration of ______ ions.
Amperometric titration can be used to determine the concentration of ______ ions.
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One disadvantage of amperometric titration is that ______ results are sometimes obtained.
One disadvantage of amperometric titration is that ______ results are sometimes obtained.
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A common example of a reducible ion is ______.
A common example of a reducible ion is ______.
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In redox titration, an oxidant and a ______ are used.
In redox titration, an oxidant and a ______ are used.
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Amperometry is a form of ______ analysis.
Amperometry is a form of ______ analysis.
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In amperometric titration, the potential is applied between the indicator electrode and the appropriate ______ electrode.
In amperometric titration, the potential is applied between the indicator electrode and the appropriate ______ electrode.
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The indicator electrode used in amperometric titration is a ______ mercury electrode.
The indicator electrode used in amperometric titration is a ______ mercury electrode.
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The diffusion current changes during titration due to varying concentration of electro- ______ ions.
The diffusion current changes during titration due to varying concentration of electro- ______ ions.
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According to Ilkovic equation, Id is the diffusion current due to ______ ions.
According to Ilkovic equation, Id is the diffusion current due to ______ ions.
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For performing amperometric titration, both substances involved should be ______.
For performing amperometric titration, both substances involved should be ______.
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A rotating platinum micro-electrode consists of a glass rod with a bent platinum ______.
A rotating platinum micro-electrode consists of a glass rod with a bent platinum ______.
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The drop time for the dropping mercury electrode is typically between ______ seconds.
The drop time for the dropping mercury electrode is typically between ______ seconds.
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Study Notes
Amperometry
- Amperometry is an electrochemical method for measuring current under a constant voltage.
- It's a quantitative analytical technique.
- Used when indicator methods are unsuitable for determining the endpoint.
- Often called polarographic titration due to similar principles.
Principle
- In amperometric titration, a constant potential is applied between an indicator electrode and a reference electrode.
- The current passing through the cell is measured during the titration.
- The indicator electrode is typically a dropping mercury electrode (DME).
- The reference electrode is usually a saturated calomel electrode.
- The concentration of the electro-reducible ion changes during titration, affecting the diffusion current.
Ilkovic Equation
- The Ilkovic equation describes the relationship between diffusion current (Id), the concentration (C) of the electro-reducible ions, the number of electrons (n) involved in the reduction, the diffusion coefficient (D), and the drop time (t) of the mercury electrode.
- Id = 607 n C D2/3t1/6 / m
Conditions for Amperometric Titration
- Both the analyte and titrant must be reducible.
- The applied potential should be in the limiting current region.
Apparatus for Amperometric Titration
- Dropping Mercury Electrode (DME)
- Capillary tube (10-15 cm) with an internal diameter of 0.05 mm.
- Drop time (1-5 seconds)
- Drop diameter (0.5 mm)
- Rotating Platinum Microelectrode (RPME).
- Glass rod with a bent platinum wire.
- Rotates at approximately 600 rpm.
- Wire contacts to a mercury reservoir to apply the potential.
Advantages of RPME over DME
- RPME can be used at higher positive potentials without oxidation issues. Unlike DME, which is limited to a lower potential range.
- RPME yields 20 times larger diffusion currents, allowing for the analysis of lower ion concentrations.
- Construction is simpler.
Types of Amperometric Titrations
- Reducible ions vs. non-reducible ions (e.g., Lead (Pb2+) vs. sulfate ions (SO42-)).
- Non-reducible ions vs. reducible ions (e.g., Chloride (Cl-) vs. silver (Ag+)).
- Reducible ions vs. reducible ions (e.g., Lead (Pb2+) vs. dichromate ions (Cr2O72-)).
- Redox titrations (oxidant and reductant) (e.g., Ferric (Fe3+) ions vs. titanous ions (Ti2+)).
- Karl Fischer titration (for water determination)
Advantages of Amperometric Titration
- Both reducible and non-reducible ions can be determined.
- Dilute solutions can be analyzed.
- The reaction can be reversible or irreversible.
- Apparatus is simple and temperature is not a critical factor.
Applications of Amperometric Titration
- Quantitative analysis.
- Determining endpoints.
- Water determination using Karl Fischer reagent.
- Amperometric detectors in HPLC can detect very low reducible ion concentrations.
- Quantification of ions or ion mixtures.
Disadvantages of Amperometric Titration
- Results may be inaccurate.
- Foreign substances should not be present in higher concentrations than the substance being analyzed.
References
- Textbook of pharmaceutical analysis, 4th edition by Dr. Ravi Sankar.
- Instrumental methods of chemical analysis by G.R. Chatwal & Sham K. Anand.
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Description
Test your knowledge on amperometric titration, redox reactions, and associated concepts. This quiz covers important aspects like the use of RPME, detection of endpoints in titrations, and the principles of current measurement in electrochemical analysis. Perfect for students familiar with analytical chemistry.
