Answer to Question #117457 in Chemistry for Edition Michael inyang

Question

How is potentiometry applied in
1. Chemical diagnostic
2. Environmental monitoring

Answer 1

Answer:

1.Potentiometry is an electrochemical (electrometric) method of research and analysis of substances based on determining the relationship between the equilibrium electrode potential φ and the thermodynamic activity a of components A, B… and C, D… (ions, molecules in liquid, solid or gas phase), which involved in the electrochemical reaction.

 There are direct potentiometry and potentiometric titration. The first is used to directly determine the value of E, usually under the reversibility of the electrode process. Non-equilibrium potentiometric measurements are performed with galvanic elements, in which the potentials on the selected indicator electrodes are mixed by nature (compromise), but a stable and reproductive dependence of the electrode potential on the solution composition is established, which in practice allows to control processes. Thus, potentiometry is used to control the preparation of hypochlorite solutions in the pulp and paper and chemical industries.

Historically, the first methods of direct potentiometry were methods for determining the hydrogen pH, in particular, using a glass electrode.

In the analysis, potentiometric titration methods are more common, which are used to determine most substances in aqueous and non-aqueous media. In potentiometric titration, the change in the potential of the indicator electrode during the titration of the test solution with a standard solution of reagent from the volume of the latter is recorded: the end point of titration (k.t.t.) .t. with the corresponding φ0. Potentiometric titration is performed using a variety of reactions: acid-base and redox interactions, precipitation and complexation. In acid-base titration methods, any electrode reversible to H + ions (usually glass) can be used as an indicator electrode. Redox titration is performed with electrodes made of precious metals (mostly with smooth platinum). In precipitation and complexometric titration methods, the indicator electrode (ion-selective or metallic) must be reversible relative to one of the ions involved in the reaction.

2.Potentiometric methods are based on the measurement of EMF. Determination with ion-selective electrodes in direct potentiometry _ is a selective method that allows you to monitor a single ion, such as wastewater or natural water. .

The advantage of the method is that the determination can be performed in colored, turbid water with suspended particles in the presence of protein substances. The disadvantages of ion-selective electrodes include their low accuracy and sensitivity, as well as the effect of pH of the solution on the determination.