Titration analysis method-oxidation-reduction titration method (1)

Redox titration refers to a titration analysis method based on redox reactions

1.

(1) Condition electrode potential

According to the potential value of the electric pair, the direction of the reaction and the completeness of the reaction can be judged

The potential of the redox couple can be expressed by the Nernst equation, such as the following half reaction:

Its Nernst equation is

In the formula, φ—the electric potential of the electric pair;

φ ^θ -the standard potential of the electric pair;

a _ox , a _Red -the activity of oxidized form and reduced form;

R—gas constant, R=8.

T—absolute temperature, K;

F—Faraday constant, F=96487℃/mol;

n—the number of electrons transferred in a half-reaction

(2) The direction of the oxidation-reduction reaction

Since the concentration of oxidant and reducing agent, the acidity of the solution, the formation of precipitation and the formation of complexes all affect the potential of the redox couple, the direction of the redox reaction may be affected under different conditions

2.

Titration analysis requires rapid reaction

The factors that affect the rate of oxidation-reduction reaction are as follows:

(1) Concentration

(2) Temperature

Some substances (such as I2) are volatile and will cause volatilization loss when heated; some substances (such as Sn ²⁺ , Fe ^2+, etc.

(3) Catalyst

In the oxidation-reduction reaction, many catalysts are added to accelerate the reaction.
For example, in the determination of chemical oxygen demand, Ag ₂ SO _{4 is} used as a catalyst
.

Related Links: Titration Analysis-Coordination Titration (4)