How to correctly write the total reaction of an electrolytic cell? To be detailed!! Thank you

According to the total reaction, write the reaction formula method of each electrode of the galvanic battery:

To write the negative electrode reaction formula first, we should first consider the reducing agent.

What ions are produced by losing electrons, and then consider whether the resulting ions will be with the electrolyte solution.

reaction, combined with the products in the total reaction, to write the negative electrode reaction formula.

Then use the total reaction equation (to be written as the ion equation.

Subtracting the negative reaction formula gives the positive reaction formula.

For example: the total reaction with KOH as the electrolyte is: Zn+2mNO2+2H2O 2MNO(OH)+ZN(OH)2, first analyze the reducing agent as Zn, so Zn is the negative electrode, it loses 2 electrons to generate zinc ions, and the zinc ions in the alkaline medium will continue to react to generate Zn(OH)2 (as can be seen from the equation, if the equation is written as ZNO, then ZNO is written), and the negative electrode reaction formula is:

Zn-2E- +2OH- Zn(OH)2, and then subtract the positive reaction formula: 2mNO2+2H2O+2E- 2mNO(OH)+2OH-.

Rechargeable battery.

, electrolytic cells.

The electrode reaction formula of the galvanic cell is the electrode reaction formula of the galvanic cell.

First of all, determine what happened to the cathode and cathode.

Anode: Sulfate.

ions, hydroxide ions.

Hydroxide ions are electrolyzed: 4oh- -4e === 2h2o + o2

Hydroxide is derived from water: 4H2O === 4H+ +4OH-

So 2H2O - 4E === 4H+ +O2

Cathode: copper ions, hydrogen ions.

Copper ions are electrolyzed (copper ion oxidation.

stronger): cu2+ +2e === cu

Trim electrons: 2 cu2+ +4e === 2cu

The two poles react to the equation: 2Cu2+ +2H2O === 2Cu + 4H+ +O2

Question: Hydroxide ions are electrolyzed: 4oh- -4e === 2h2o + o2 This step is understood that hydroxide is derived from water: 4h2o === 4h+ +4oh- But why is there this step?

Answer: This is the ionization of water because the hydroxide in the solution is derived from water.

Q: Is this step added to all celles?

Answer: Not necessarily, when the hydrogen ions or hydroxide ions ionized by water are not reacted, they are not added, for example, electrolytic CuCl2 is copper ions and chloride ions.

is electrolyzed. Q: As long as the anode has 4oh- -4e === 2h2o + o2 this step, then 4h2o === 4h+ +4oh- this step must be added? It can be understood that no.

A: Not necessarily, maybe hydroxide is from alkali and not water.

Q: How do you judge that? 、 = =

Answer: This is very easy to judge: if there is an acid, then the hydrogen ions come from the acid (ignoring the hydrogen ions ionized by water) If there is a base, then the hydroxide is from the alkali (ignoring the hydroxide ionized by water).

Hope you understand. Hope!

The reaction formula of different electrolytes will be different, and the general steps to solve the problem are as follows:

1) Correctly write the electrode reaction formula of the anode and cathode respectively; (2) The electrode reaction formula of the anode and cathode has an equal number of electrons transferred; (3) The electrode reaction formula of the anode and cathode is added on both sides respectively; (4) merging similar items; (5) Approximate minutes when there is merit; (6) Check the conservation of quality, both!

Generally speaking, the writing of galvanic battery electrode reaction formula should pay attention to the following four points: 1First of all, judge the positive and negative electrodes of the original power supply If the positive and negative electrodes of the battery are wrongly judged, the electrode reaction must be written incorrectly.

In general, the more reactive metals lose electrons and are the negative poles of galvanic cells, but not absolutely. For example, magnesium sheets and aluminum sheets are inserted into the sodium hydroxide solution to form a galvanic battery, although magnesium is more active than aluminum, but because the aluminum and sodium hydroxide solution react to lose electrons and are oxidized, aluminum is the negative electrode, and the electrode reaction at this time is: Negative electrode:

2AL6E ==2AL3+ Positive: 6H2O +6E ==6OH +3H2 or 2AL3++2H2O +6E + 2OH ==2ALO2 + 3H2 For example, when copper and aluminum sheets are inserted into concentrated nitric acid at the same time to form a galvanic battery, due to the passivation of aluminum in concentrated nitric acid, the copper loses electrons and the negative electrode of the galvanic cell is oxidized, and the electrode reaction at this time is: Negative electrode:

Cu 2e ==Cu2+ cathode: 2NO3 + 4H++2E ==2NO2 +2H2O2Pay attention to the acidity and alkalinity of the electrolyte solution The electrode reaction that occurs on the positive and negative electrodes is not isolated, it is often closely related to the electrolyte solution.

For example, hydrogen and oxygen fuel cells are divided into acid and basic two, electrode reaction in acidic solution: negative electrode: 2H2 4E ==4H + positive O2+ 4H++ 4E ==2H2O If it is in alkaline solution, there can be no H+, and in the same acidic solution, OH cannot appear.

Since fuel cells such as CH4 and CH3OH are in alkaline solution, carbon is in the form of CO32 ions, so CO2 is not released. 3.Also pay attention to the number of electrons transferred In the same galvanic cell, the total number of electrons lost by the negative electrode must be equal to the total number of electrons gained by the positive electrode, so when writing the electrode reaction, it is important to pay attention to the conservation of charge.

This avoids errors or errors in the calculations, as well as errors caused by writing the total reaction equation from the electrode reaction formula or rewriting the electrode reaction equation from the total equation. 4.Grasp the total reaction equation Theoretically, any spontaneous redox reaction can be designed as a galvanic cell.

The sum of the two electrodes gives the total reaction equation. Therefore, for an unfamiliar galvanic cell, as long as you know the total reaction equation and one of the electrode reactions, you can write another electrode reaction. (

According to the total reaction, write the reaction formula method of each electrode of the galvanic battery:

First write the negative electrode reaction formula, first consider what ions are generated by the electron loss of the reducing agent, then consider whether the generated ions will react with the electrolyte solution, and then write the negative electrode reaction formula in combination with the products produced in the total reaction.

Then subtract the negative reaction equation from the total reaction equation (to be written as the ion equation) to get the positive reaction formula.

For example: the total reaction with KOH as the electrolyte is: Zn+2mNO2+2H2O 2MNO(OH)+ZN(OH)2, first analyze the reducing agent as Zn, so Zn is the negative electrode, it loses 2 electrons to generate zinc ions, and the zinc ions in the alkaline medium will continue to react to generate Zn(OH)2 (as can be seen from the equation, if the equation is written as ZNO, then ZNO is written), and the negative electrode reaction formula is:

Zn-2E- +2OH- Zn(OH)2, and then subtract the positive reaction formula: 2mNO2+2H2O+2E- 2mNO(OH)+2OH-.

First of all, keep in mind the negative oxidation reaction, the positive reduction reaction.

1.Determine the discharge material and its oxidation products on the negative electrode, and the discharge material and its reduction product on the positive electrode.

2.Considering the reaction between the discharge product and the electrolyte, for example, O2 in a strong acid solution gets electrons at the positive electrode to form OH-, and OH- is then neutralized by H+, so it cannot be written as O2+2H2O+4E-=4OH- but O2+4E-+4H+=2H2O!

3.Considering the conservation of mass, the conservation of charge, the conservation of electrons of gain and loss.

4.The positive electrode reaction formula is generally more difficult to write than the negative electrode, usually the negative electrode reaction equation is written first, and then the total reaction formula is written, and the positive electrode reaction formula can be obtained by subtracting. However, in order to strengthen your proficiency, it is recommended that you try to write positive reactions when you first learn, practice makes perfect.

The above are a few of my own summaries.,If you have any questions, you can hi me.。。

Negative oxidation. Positive electrode reduction.

Write the anode reaction first and then the cathodic reaction.

Key points: An electrolytic cell is a device that converts electrical energy into chemical energy. The anode of the electrolytic cell is the positive electrode of the battery, which occurs.

Internal oxidation reaction, loss of electrons, and increased valency of element accommodation;

The cathode of the electrolytic cell undergoes a reduction reaction to the positive electrode of the battery, and the electrons are obtained, and the valency of the elements decreases.

If a metal (other than platinum and gold) is used as an anode, the metal loses electrons and generates metal cations into the solution.

How to write a reactive formula:

Anode reaction: Look at the reducing substance in the solution (if it is a metal (except platinum and gold) as an anode, it is a metal), then the reducing agent loses electrons.

Cathodic reaction: Look at the oxidizing substances in the solution, then the oxidizing agent gets electrons.

In solution, cation discharge sequence: Ag+>Hg2+>Fe3+>Cu2+>H+(acid)>Pb2+>SN+>Fe2+>Zn2+> H+(H2O)>Al3+>Mg2+>Na+>Ca+>K+

Hope it helps.

Anodizing, cathode bai

Restore. Anodized hair.

DU bio-oxidation reaction, chemical valence increased;The DAO cathode undergoes a reduction reaction, and the valency decreases.

What happens to the yin and yang capacitance poles, you need to remember the discharge order, and react first in the front:

Anion discharge sequence: S2-, I-, Br-, Cl-, OH-, oxynate ions.

Sequence of cation discharge: au pt ag hg cu h pb sn fe zn al mg na ca k (both in ionic form).

Example of electrolysis Na2SO4:

Anode (oxidation reaction occurs, the valency increases, and the anions of this solution have only oh- and sulfate ions. oh- discharges first, so 2oh--2e-=h2o+1 2o2)

The cathode (a reduction reaction occurs, and the cations in this solution are only na, hydrogen ions. From the above cation ion discharge sequence, h+ is discharged first (reaction occurs), so 2h++2e-=h2)

Through the cathode and cathode reaction, it is found that it is the same as electrolyzed water, and the essence is electrolyzed water.

1: It is connected to the positive electrode of the power supply as the anode, and the negative electrode is connected to the cathode;

Two: ions move, cations move to the cathode, and anions move to the anode.

3. Judge the electrode reaction according to the ions in the solution; During electrolysis, how to determine the electrode (anode, cathode) product.

1) Judgment of anode products.

First of all, look at the electrode, if it is an active electrode (before the metal activity sequence table AG), the electrode material loses electrons, the electrode is dissolved, and the anions in the solution cannot lose electrons. In the case of inert electrodes (PT, AU, graphite), then look at the electron-losing ability of the ions in the solution. At this time, it is judged according to the anion discharge sequence, and the anion discharge sequence:

S2 i br cl oh oxylate f

2) Judgment of cathode products.

Directly judged according to the cation discharge sequence, the cation discharge sequence: AG+ Hg2+ Fe3+ Cu2+ H+ (acid) Pb2+ SN2+ Fe2+ Zn2+ H+ (water) Al3+ Mg2+ Na+ Ca2+ K+

Keeping in mind the order of activity of the elements, the relatively reactive lost electrons are oxidized and the inactive electrons are reduced.

The scientific method is to memorize the discharge sequence and then write the electrode reaction formula based on the electrons gained and lost.