What is Electrochemistry Used for? || Electrochemistry example

Electrochemistry is the science that studies the phenomenon of charged interfaces formed by two types of conductors and the changes that occur on them. The interaction between electrical and chemical reactions can be accomplished through batteries or can be achieved by high-voltage electrostatic discharge (such as the conversion of oxygen into ozone through silent discharge tubes).

The two are collectively referred to as electrochemistry, which is a branch of electrochemistry, called discharge chemistry. Because of the special name for discharge chemistry, electrochemistry often refers specifically to the “science of batteries.”

Electrochemistry has now formed a number of branches such as synthetic electrochemistry, quantum electrochemistry, semiconductor electrochemistry, organic conductor electrochemistry, spectral electrochemistry, and bioelectrochemistry.

Electrochemistry example

Electrochemistry has been widely used in chemical, metallurgy, machinery, electronics, aviation, aerospace, light industry, instrumentation, medicine, materials, energy, metal corrosion and protection, environmental science and other scientific and technological fields. 

At present, research topics that are of great concern in the world, such as energy, materials, environmental protection, life sciences, and so on, are related to electrochemistry in various ways.

Primary battery

The primary battery uses the difference in metallization between the two electrodes to generate a potential difference, which causes the flow of electrons and generates a current. Also known as non-battery, it is a type of electrochemical battery. It can be converted into electrical energy, which simply means that it cannot be restored, as opposed to a battery.

Primary batteries are devices that convert chemical energy into electrical energy. Therefore, according to the definition, ordinary dry cells and fuel cells can be called primary cells.

Basic conditions for forming a primary battery:

1, of two different inert metal (i.e., one is the active metal one is not), the one metal or graphite (Pt and graphite electrodes are inert, i.e., does not itself electronic gains and losses) like an inert electrode Insert into the electrolyte solution.

2. Connect with a wire and insert it into the electrolyte solution to form a closed loop.

3. A spontaneous redox reaction should occur.

How galvanic cells work

The primary battery is an oxidation reaction and a reduction reaction that can spontaneously perform a redox reaction on the negative electrode and the positive electrode of the primary battery, respectively, thereby generating a current in an external circuit.

The judgment of the electrode of the primary battery:

Negative electrode: one pole where electrons flow out; one pole where oxidation reaction occurs; one pole with more active metal.

Positive electrode: one pole where electrons flow in; one pole where reduction occurs, one pole of relatively inactive metal or another conductor.

In a galvanic cell, the external circuit is electronically conductive and the electrolyte solution is ionically conductive.

The judgment of the primary battery:

(1) Analyze whether there is an external circuit, an electrolytic cell with an external power source, and a primary battery if there is no external power source; then analyze and judge based on the formation conditions of the primary battery.

There is a difference in the activity of the conductor (the electrodes of the fuel cell are generally inert electrodes), look at the solution-the two poles are inserted into the solution, look at the circuit-a closed-loop or direct contact between the two poles.

(2) When multiple cells are connected, but there is no external power supply, the cell with the most active difference between the two poles is the primary battery, and the other cells can be regarded as electrolytic cells.

Cell

An electrolytic cell is a device that converts electrical energy into chemical energy.

Electrolysis is the process of passing a current through an electrolyte solution (or a molten electrolyte) to cause a redox reaction at the anode and cathode.

Conditions under which the electrolytic reaction occurs:

① Connect DC power

②Connected to the negative electrode of the power supply as the cathode

Anode: Connected to the positive pole of the power source as the anode

③ Both poles are in an electrolyte solution or molten electrolyte

④Two electrodes form a closed circuit

Energy conversion in the electrolysis process (device characteristics):

Cathode: Must not participate in the reaction is not necessarily an inert electrode

Anode: Not necessarily participating in the reaction or necessarily an inert electrode

Electrolysis results:

New matter is formed at the poles

Electrolyte electrode reaction equation writing:

Anode: active metal—electron loss of electrons (except Au, Pt, Ir); inert electrode—anion loss of electrons in solution

Note: Electron loss ability: active metal (except Pt Au)> S2-> I-> Br-> Cl-> OH-> oxygenate (NO3-> SO4 2-)> F-

Cathode: cations in solution get electrons

Note: The ability to gain electrons: Ag +> Hg2 +> Fe3 +> Cu2 +> H + (acid)> Pb2 +> Sn2 +> Fe2 +> Zn2 +> H2O (water)> Al3 +> Mg2 +> Na +> Ca2 +> K + (ie, the reverse of the active metal sequence table)

Correspondence relationship: anode connected to the positive electrode of the power supply, and a cathode connected to the negative electrode of the power supply.

Rule: The ions before aluminum (containing aluminum) do not discharge, the ions after hydrogen (acid) discharge first, and the ions after aluminum before hydrogen (acid) depends on the conditions.

The electrolysis law of the four types of electrolysis type 

① Electrolyzed water type (strong alkali, oxoacid, oxo acid salt of active metal), the pH is determined by the acidity and alkalinity of the solution. When the pH decreases, the solution is neutral but the pH does not change. Electrolyte solution recovery-add appropriate amount of water.

② Electrolytic electrolyte type (anaerobic acid, anaerobic acid salt of inactive metal, etc.), the pH of anaerobic acid increases, and the pH of an anaerobic acid salt of inactive metal do not change. Electrolyte solution recovery—add an appropriate amount of electrolyte.

③ Hydrogen-generating alkali type (active anaerobic acid salt), the pH becomes large. Electrolyte solution recovery-add the same acid as the anion.

④Oxygen-generating type (oxygenates of inactive metals), pH becomes smaller. Electrolyte solution recovery-add the same base or oxide as the cation.

Separation method

There are four methods for separating metal ions and organic molecules in solution by electrochemical means.

The controlled potential electrolytic separation method

When two or more metal ions are present in the solution, if their reduction potentials are similar, they will be reduced and precipitated during electrolysis, which will not achieve the purpose of separation. The choice of potential depends on the experimental conditions.

When applying this method, the concentration of the ion to be electrolyzed later cannot exceed the concentration of the ion to be electrolyzed first.

Mercury cathode electrolytic separation method

When H □ is reduced on the mercury cathode, it has a large overvoltage, so it can separate some easily reduced metal ions in the acidic solution so that some heavy metals (such as copper, lead, cadmium, and zinc) are deposited on the mercury cathode.

In addition, amalgam is formed while retaining a small number of ions that are not easily reduced, such as alkali metals, alkaline earth metals, aluminum, iron, nickel, chromium, titanium, vanadium, tungsten, silicon and the like.

Internal electrolytic separation

In an acidic solution, an internal electrolytic cell can be formed by utilizing the difference in metal oxidation-reduction potential, which is electrolysis can be performed without applying an external voltage. 

For example, from a large number of separating trace copper lead, sulphuric acid solution in a ratio of Cu Pb is first reduced, and therefore may be used as a grid electrode is connected to the platinum electrode, the composition of a cell, it produces a spontaneous electromotive force derived from Pb Oxidation and reduction of Cu. 

This electromotive force enables the reaction to proceed until the current approaches zero, and the internal electrolytic cell is no longer functional. Internal electrolysis can separate a small amount of easily reduced metal ions. The disadvantage is that the electrolysis is slow, so it is not widely used.

Electrodialysis

Ions or charged particles in a liquid can migrate under the influence of an electric field. Due to the different nature of the ions, the rate of migration is different, and the direction of positive and negative charges is also different. 

When a DC voltage is applied to the two poles of the battery, some organic compounds can be separated. For example, this method is commonly used in clinical experiments to study proteins. After a sample is placed on a carrier, after applying an electric field, the charged particles migrate along with the carrier to the oppositely charged electrode.

They are separated due to different moving rates. The serum protein is divided into five parts. Improve the experimental technique to make the width of the concentrated spots reach about 25 microns, and then perform electrodialysis to divide the serum protein into twenty very clear parts.

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