ELECTROCHEMICAL METHOD OF ANALYSIS
Electro analytical methods are concerned with the interplay between electrictiy and chemistry, namely the measurements of electrical quantities, such as current, potential, or/and their relationship to chemical parameters.
If electrical parameter : E-Potentionmetry , R-conductometry, I- voltametry,coulometry
MAIN BRANCHES OF ELECTROANALYTICAL TECHNIQUES:-ENN
- INTERFACIAL METHODES :- a. STATIC METHODS (I=0)→POTENTIOMETRY (E)
b. Dynamic Methodes (I>0) it is also divided into two types
1. CONSTANT CURRENT→ COULOMETRIC TITRATION {Q=IT}
2. CONTROLLED POTENTIAL → VOLTAMETRY (I=FE)
↓
AMPEROMETRIC TITRATION
PARAMETERS OF ELECTRICITY :-
- CURRENTS (I):- 1 AMPERE IS THE CURRENT WHICH WHEN FLOWS FOR 1 SEC, OR 1 Ampere is about 6.26×1018 e¯ Passing a point in 1 sec.
- Quantity :- unit-coulomb SI unit faraday 1 coulomb is the qty of electricity equal to 1 ampere current allowed to flow for 1 sec. 1 faraday= 96,500 coulomb = 1 mole e¯
- Electromotive force :- It is the force which causes e¯ to move. 1 volt is the potential req. to force 1 ampere current through a resistance of 1 ohm.
- Resistance :- It is an inherent property of metal to retard the flow of electricity. Unit : Ohm. 1 Ohm is the resistance at 0°C of a column of mercury with a uniform cross-section and 106.3cm long weighing 14.4251gmHg.
- Conductance:- Inherent property of the material to allow electricity to pass through. units:-Ohm¯ OR SI units :- Siemens
- Electrode :-It is simple wire like terminal or plate / rod use to pass electricity through the solution & to send electricity generated in solution .
Types of electrodes :-
- REFERENCE ELECTRODE/ NON-POLARIZABLE ELECTRODES :- An electrodes whose potential remains constant and against which other potentials can be measured: SCE (Saturated calomel electrode),Hydrogen electrode , Ag-Ag CL electorde etc.
- Indicator/polarizable electrodes :- The electrodes whose potential is a function of the analyte concentration Eg: Glass Electrodes – most widely used, platinum electrodes , metalic electrodes
COMPARISON OF VARIOUS ELECTROCHEMICAL METHOD OF ANALYSIS
| TECHNIQUE | CONSTANT PARAMETERS | PARAMETERS TO BE MEASURED |
| Potentiometry | current | Potential/Voltage |
| Potentiometry titration | Current | GRAPH:- Potentials vs ml of titrant |
| Conductometry | Potential | Conductance |
| Conductometry titration | Potential | GRAPH:- Conductance vs ml of titrant |
| Polargraphy | Concentration | GRAPH:-Diffusion current vs applied potentials |
| Amperometry | potential | GRAPH:-diffusion currents vs ml of titrant |
MCQ
1. 1 mole e¯ =
a.90000 coulomb
b. 96,500 coulomb
c.133300 coulomb
d.96,400 coulomb
2.which type of graph shows in Potentiometry titration ?
a.diffusion currents vs ml of titrant
b.Potentials vs ml of titrant
c.Diffusion current vs applied potentials
d. Conductance vs ml of titrant
3. Which type of graph shows in Amperometry ?
a.diffusion currents vs ml of titrant
b.Potentials vs ml of titrant
c.Diffusion current vs applied potentials
d. Conductance vs ml of titrant
4.which type of graph shows in Conductometry titration ?
a.diffusion currents vs ml of titrant
b.Potentials vs ml of titrant
c.Diffusion current vs applied potentials
d. Conductance vs ml of titrant
5.which is not a reference electrodes ?
a. SCE
b.Ag-Ag CL electrode
c.Hydrogen electrode
d.platinum electrode
6. which is not a Indicator electrodes ?
a. metallic electrodes
b.Glass Electrodes
c.platinum electrodes
d.Hydrogen electrode
ANSWER KEY :-
1.B
2.B
3.A
4.D
5.D
6.D