The conductance is defined as the current flow through the conductor. In other words, it is defined as the reciprocal of the resistance. This method is mainly used for the determination of the physico-chemical properties of the compounds. The movement of the ions is mainly depended on the concentration of the ions.
|Published (Last):||9 September 2009|
|PDF File Size:||1.90 Mb|
|ePub File Size:||10.25 Mb|
|Price:||Free* [*Free Regsitration Required]|
The conductance is defined as the current flow through the conductor. In other words, it is defined as the reciprocal of the resistance.
This method is mainly used for the determination of the physico-chemical properties of the compounds. The movement of the ions is mainly depended on the concentration of the ions. This replacement of the ions with the other ions shows the conductance increase or decrease. This is done mainly by the replacement of the hydrogen ion with other cation. The sample solution is placed on the cell which is composed of platinum electrodes.
These are calibrated with the help of known conductivity of the solution, for example, standard potassium chloride solution. The value is 0. The following are the different bridges used for the measurement of the conductance: Kohlrausch bridge: It consists of a meter bridge wire AB with a fixed resistance R on both the ends.
All these are operated by the battery. Headphone is used for the detection of the conductance difference. Kohlrausch bridge Conductivity cell: These conductivity cells are made up of glass. These are commonly employed by dipping in the analyte solution.
It is composed of pair of electrodes placed at a constant distance. There are mainly three types of cells used as conductivity cells: Type A: This consists of the electrodes placed at a large distance and is used for the measurement of the high conductance.
Conductivity cell Type B: In this type, the cell is dipped in the sample solution to measure the conductance in the titrations. Conductivity cell Type C: In this type, large electrodes are placed with small distance. This type cell is mainly used for the measurement of the low conductance. They are made up of glass fitted with the platinum electrodes. The electrodes are made up of platinum sheets. These electrodes are fixed in a constant distance and are sealed in the connected tubes.
To avoid the polarisation effect, these electrodes are coated with the platinum black. Then 0. On passing the current, chloroplatinic acid under goes electrolysis and the electrodes are blackened. Then these electrodes are repeatedly washed with the distilled water and finally with the conductivity water. The conductivity water is the water obtained by treating the distilled water with small amount of sodium hydroxide and potassium permanganate.
Here the induction coil is used for inducing current. The temperature is maintained constant with the help of the thermostat. Then the cell is connected to the resistor box R and the alternating current is passed through the cell with the help of induction coil. This is because of the ions mobility by increasing the temperature.
Concentration of the sample solution: The concentration of the solution is inversely proportional to the conductivity of the sample solution. The conductance is decreased with the increase in the concentration. Hence diluted solutions are used for the conductivity measurements. Number ions present in the sample solution: This is mainly based on the dissociation of the compounds into ions.
That is mainly of the number of ions present in the solution. The number of ions present in the solution is directly proportional to the conductance. Strong electrolytes completely dissociate into ions and have high conductance. Charge of the ions: Negative charge of the ions increases the conductivity where as the positively charged ions decreases the conductivity. Size of the ions: The conductivity is inversely proportional to the size of the ions.
That is the increase in the size of the ions increases the conductivity. Types of the Conductometric Titrations Acid—base titrations: In this method, the conductance of the hydrogen ions and hydroxyl ions are compared with the conductivity of the sample solution.
This shows the decrease in the conductivity. After completion of the reaction, the excess addition of the NaOH shows the increase in the conductivity.
The plot between the conductivity and the volume of the titrant shows the V-shaped curve. Strong acid with strong base curve Strong acid with weak base: For example, titrations of the strong acid such as HCL with the weak base such as the ammonium hydroxide.
The excess addition of the NH4OH does not show the change in the conductivity. Then the plot between the conductivity and the volume of the titrant shows the plateau.
Strong acid with weak base titration curve Weak acid with a strong base: The weak acid such as acetic acid is titrated with the strong base such as sodium hydroxide.
Learn how and when to remove this template message Look up conductometry in Wiktionary, the free dictionary. Conductometry is a measurement of electrolytic conductivity to monitor a progress of chemical reaction. Conductometry has notable application in analytical chemistry , where conductometric titration is a standard technique. In usual analytical chemistry practice, the term conductometry is used as a synonym of conductometric titration, while the term conductimetry is used to describe non-titrative applications. It was also around this time when Willis Whitney, who was studying the interactions of sulfuric acid and chromium sulfate complexes, found the first conductometric endpoint. Conductometry was further improved with the development of the glass electrode, which began in The equivalence point is the point at which the conductivity undergoes a sudden change.
In that various characteristic like quality control, pollution control, process monitoring and managing require performing conductivity measurement regularly. Conductivity is the measure of the ability of the material to carry out electrical current. Conductivity measurement of the sample solution provides the degree of electrical conductivity in the definite quantity of the solution. The electrical conductivity of the solution is similar to the number of ions available in it and therefore the conductivity measurement of a solution will give a reading of the solution. The principle by which the system measures the conductivity is simple. There are two conductivity plates are situated in the sample and potentially apply to them usually ac voltage and after that, the current is measured.