Potentiometry | Assignment | AEI

Potentiometry 

1. Explain The Teams :

(A) potentiometry :

→ In chemical analysis, potentiometry is method in which the potential between two electrode is measured while the electric current between the electrodes is controlled.

→ It is measurement of electric ometer.

→The potential of one electrode known as the working or indicatos electrode f gesponds to analyte's activity. The other electrode on reference electrode has known fixed potential. 

(B) Polarography : 

→ The planography is an electrochemical method of analysis based on the measurement of cument flow resulting from the electrolysis of the solution at a polandsable micro-electrode as a function of applied voltage. 

→ Polanography is based pion principle that gradually increasing voltage is applied between 2 electrodes. 1 of which is polarisable  ( droping Mercury electrode ) and other is non polarisable electrode f current flowing between  2 Electrode is reconded. 

→ Diffusion current is used for determination of concentration of substance.  

(c) Diffusion Current: 

→It arises due to the migration of analyte species from the bulk of solution. towards mico electrode and it's magnitude is depends on law of diffusion. 

→Current caused by diffusion of Depolarization potential enables identification of ion's present in soln & by measuring diffusion current their conc. in is calculated. 

(d) Define: pH  

→ pH is measure of H+ ions present in any solution.

→ It tells you how acidic your solution is. 

→ Importance Of Ph In Environmental Field: 

• Disinfection 
• corrosion control 
• chemical coagulation.
• sludge Dewatering 
• Microorganism in biological Treatment.  

2. Explain the following instrument : 

(1) Potentiometer : 

→ The principle of a Potentiometer is that the potential dropped across a segment of wire of uniform crogs section carrying a constant current is directly proportional to its length. 

→ The potention meter is simple device used to measure the electric potential. 

(2) Ion- selective Meter : 

→ Ion - selective meters maybe configured to measure one of several different types of ion, depending on the electrode used.

• A sensing electrode 
• A reference electrode 

→ These two electrodes may be built into the same probe on use two separate probes. 

(3) pH meter : 

→ The principle of pH meter depends upon the exchange of ion from sample solution to the inner solution (pH 7 buffer ) of glass electrode thisrough the glugs membrane.

→ The porosity of the glass membrune decreases with the continuous use that decreases the perfor mance of the probe. 

(4) Do Meter :

→ The Basic underlying the electrochemical determination of oxygen concentration is the use of membrane covered electro-chemical sensors. 

→ If the anode is made of silver, the meter applied the required voltage. 

3. Explain the working principle of ion selective meter, pH meter and Do meter and Electrodes. 

• Ion-selective Meter : 

→The ion selective electrode works based on principle of a galvanic cell. 

- It consists of a reference electrode, ion selective membrane and voltmeter. 

- The Transport of ions from an area of high concentrictions to low concentration through The selective binding of ions with of the membrane creates a the specific sites potential difference. 

- The potential is measured with respect to a stable reference electrode having a constant potential of net change is determined.  

- The difference in potential between the electrode & the membrane deped depends on the activity of the specific ion in solution.

- The strength of the net charge measured is directly proportional to the concentration of the selected son.  

• PH Meter : 

- A pH meter will be made up of a probe which itseIf is made up of two electrodes.  

- This probe passes electrical signals to a meter. 

- which displays the reading in pH units. 

- The glass probs has two electrodes because one is Jalass sensor electrode f other is a reference electrode. 

- Some pH meter do have separate probes in which case, one would be the sensor electrodes & the referce point. 

- Both electrode are hollow bulbs a contain in a Ichloride solution with a silver chloride wire suspend into it. 

- The glass sensing electrode has a bulb made upe of a vens special glass couted with silicca & metal salts. 

- The glass sensing electrode measures the pit as the concentration of hydrogen ion surrounding the tip of thin walled glass bulb.  

- Chemical potential between a known liquid inside the glass electrode fi unknown liquid outside.

- Because the thin glass bulb allows mainly the a angle & small hydrogen ion to intract with the glass. 

- The glass electrode measures the electrochemical circuit also a reference electrode is needed.

4. Along with meat sketch explain following electrodes. 

• pH Electrode:  

- The combination or pH electrode measures the difference in potentials between the two sides in the glass electrode

- To measure the potentials it must be a closed circuit.

- The circuit is closed through the internal solutions of the electrode and the external solution that is being measured & the pH meter.

- As the electrode is immersed in the test solution the

glass bulb senses the Htions as a millivolts (mu) due to the positive charge of the lit ions. 

- The Electroly te or internal solution picks up mv

signal foom glass bulb.

- That signal is then passed to the internal electrode. 

- The Ag/Ag cl wire than passes that signal to the electrod cable that leads to the metter.

- The circuit is closed by a minute amount of internal solution from the reference electrode flowing through la posous membrane made of a ceramic wick.

- This membrane or junction as it is called is located the electrode body. 

• Ion- selective Electrode : 

- Ion-selective electrode abo known as a specific ion electrode.

- It is a transduce or for that converts the activity

of a spefict specific ion dissolved in a solution into an electrical potential, which can be measured by a voltmeter.on pH meter.

- An ideal ion-selective electrode consists of a thin membrane gross which only the intended ion be transported.

- The transport of ions from a high conc. to a low. Lone through a selective binding with some sites within the membrane creates a potential difference.

- Ion selective electrodes work on the basic principle of the galvanic cell.

- By measuring the electric potential generated acroIss 4 membrane by "selected" ions, & comparing it to a reference electrode, a net charge determined.

- The strength of this charge is directly proportional to the concentration of the selected ions.

The basic formula is given for the galvanic cell.

Ecell = EISE- Eref

• Do Electrode 

→ An inert metal such as gold on platinum anode and silver is use used for anode.

→ They are electrically connected with kcl or other electrolytic solution.

→ The complete cell is separated from sample by means of gas.

→ Permeable membrane usually made of polyethylene or Teflon.

→ When potential of about 0.5-0.8 v. is applied acro ss the anode & cathode any oxygen that passes

through the membrane will be reduced at cathode causing a current to flow.

→ The magnitude of current produced, is dissectly proportional to amount of Oxygen in sample.