DETERMINATION OF RATES OF REACTION
In Chemical Kinetics two methods are employed for the determination of rate of reaction:
(a) Chemical Methods
(b) Physical Methods
(a) Chemical Methods:
In a chemical method generally samples are drawn from the reacting vessel at regular intervals of time. The amount of reactant or product present at that time is generally found by titrating the sample against a proper reagent. The difference between the results of titration of samples with the time intervals is used to determine the rate of reaction. For example in the hydrolysis of methyl acetate in acidic medium, the amount of acetic acid formed is measured at regular intervals by titrating the chilled samples against standard alkali. With the passage of time amount of acetic acid in a sample increases till reaction goes to completion.
(b) Physical Methods:
In chemical laboratories different physical methods are utilized such as:
(i) Refrectrometric Method:
In this method change in refractive index of reactants and products is estimated with regular intervals of time.
(ii) Spectroscopic Method:
Here absorption of U\/ or IR radiations carried out through spectrometer.
(iii) Calorimetric Method:
Here change in colour intensity is observed periodically.
(iv) Conductivity Method:
In this method change in electrical conductivity is measured through conduct meter.
(v) PH Method:
Here change in PH is observed by the help of PH – meter.
(vi) Polarimetric Method:
In this method change in optical rotation of plane polarized light is observed in regular intervals of time so that a certain rate of reaction is determined.