A question about the chemistry of sodium carbonate hydrolysis

The previous hydrolysis only affects the ionization of water, and does not include the ionization of water, which is equivalent to passive ionization of water.

H2O <==> H+ +OH- is the active ionization of water.

Also, the first one is the ionization equation, not hydrolysis.

na2co3==2na+ +co32-

co32- +h2o <==> hco3- +oh-hco3- +h2o <==> h2co3 + oh-h2o <==> h+ +oh-

Formula 1 is the ionization of carbonic acid, formula 2 is the hydrolysis of carbonate, formula 3 is the hydrolysis of bicarbonate, and formula 4 is the ionization of water.

Where, 2,3 is the decomposition of water into H+ and OH- but this is produced by the action of carbonate and bicarbonate. At this time, there are still water molecules in the aqueous solution that are not ionized by these weak acid groups.

If you don't consider equation 4, you can infer that the solution is alkaline, but this will mislead others into thinking that there are no hydrogen ions in the solution at this time, that is, the pH value will be very large (very alkaline), which is actually wrong.

**Conservation problem, to consider the ionization and hydrolysis in the solution, find all the ions and molecules, in order to study the conservation relationship The fourth ionization equation reflects the last hydrogen ions present in the solution, and the first two hydrolysis equations reflect the hydrogen ions that are hydrolyzed and combined, HCO3- binds 1, H2CO3 binds 2. Therefore, the following equation is listed when considering the conservation of hydrogen ions and hydroxide ions produced by all waters:

c（oh-)＝c(h+)＋c(hco3- )2c(h2co3)

2c(H2CO3) is preceded by 2 because (H2CO3 binds 2 hydrogen ions ionized from water).

The middle two should be considered hydrolysis equations, not ionization equations.

Equation one is the complete ionization of sodium carbonate.

Equation 2 is the primary hydrolysis of carbonate ions, and Equation 3 is the secondary hydrolysis.

Equation 4 refers to the partial ionization of water molecules.

The ionization of water molecules is inevitable in most solutions, and it is important to determine the ion concentration.

Your understanding is correct. Clause.

Second, the third hydrolysis is to include the ionization of water, and the reason why it is required to write the fourth ionization of water is only to clarify the role and principle of water in the hydrolysis process.

These four equations include the various ions in the aqueous solution of all sodium carbonate. The degree of ionization is also ranked from high to low.

And isn't the ionization of water the fourth? Why write about it?

No, water ionization is the change of water molecules, which happens on its own, and the first two are carbonate and bicarbonate reaction in aqueous solution, and they are weak acid groups, so hydrolysis occurs, and hydrogen ions are seized from the water, and I ask you, if the first two are included, as you said, then when bicarbonate and hydrochloride take the hydrogen ions in the water, does the concentration of hydroxide in the solution increase, does the concentration of hydrogen ions decrease, and whose ionization reaction moves, which promotes the ionization of water?

Sodium carbonate. The degree of hydrolysis is greater than sodium bicarbonate.

It is based on the concentration of the same substance.

The alkalinity of the next two is judged.

For strong bases and weak acids.

In the case of salt, hydrolysis is greater than ionization, indicating that the solution is alkaline.

The specifics can be explained by the degree of hydrolysis (primary hydrolysis and secondary water) and ionization.

1) For NaHCO3, bicarbonate.

Hydrolysis and ionization occur.

Hydrolysis equation: HCO3-+H2O=H2CO3+OH-, OH- will be released, making the solution alkaline;

The ionization equation: HCO3-=(CO3)2-+H+, H+ will be released, making the solution acidic;

However, since the hydrolysis of bicarbonate is greater than ionization, C(OH-)>C(H+), so the sodium bicarbonate solution is alkaline.

Note: Hydrolysis or ionization here generally refers to the hydrolysis or ionization of the corresponding weakly acidic acid. )

2) For Na2CO3, hydrolysis of carbonate occurs.

CO3)2-+H2O=HCO3-+OH-, which will release OH- and make the solution alkaline;

HCO3-+H2O==H2CO3+OH-, which also releases OH-, but the degree of secondary hydrolysis is much smaller than that of primary hydrolysis (negligible);

Of course, at this time, the bicarbonate obtained by first-stage hydrolysis will also be ionized in the field to obtain H+, but with the first hydrolysis reaction.

Mainly. Secondary hydrolysis and especially ionization of bicarbonate can be ignored. Therefore, the Na2CO3 solution is alkaline.

It can be seen from the above that the degree of hydrolysis of sodium carbonate and sodium bicarbonate can be reflected by their primary hydrolysis, and the amount and concentration of the hydrolyzed oh- substance can reflect the degree of hydrolysis, that is, the alkalinity of the two can be judged by the amount concentration of the same substance, because the alkalinity of sodium carbonate is much greater than that of sodium bicarbonate at the amount concentration of the same substance, so the degree of hydrolysis of sodium carbonate is greater than that of sodium bicarbonate.

The degree of hydrolysis of sodium carbonate is greater than that of sodium bicarbonate, which is judged by the alkalinity of the two at the amount and concentration of the same substance. For strong alkalis and weak salts, hydrolysis is greater than ionization, indicating that the solution is alkaline. It can be explained by the degree of hydrolysis (primary hydrolysis and secondary water) and ionization.

In the case of NaHCO3, bicarbonate is hydrolyzed and ionized. Hydrolysis equation: HCO3-+H2O=H2CO3+OH-, OH- will be released, making the solution alkaline; Ionization equation:

HCO3-=(CO3)2-+H+, which will release H+ and make the solution acidic; However, since the hydrolysis of bicarbonate is greater than ionization, C(OH-)>C(H+), so the sodium bicarbonate solution is alkaline. (Note: The hydrolysis or ionization here generally refers to the hydrolysis or ionization of the corresponding weakly acidic acid.)

In the case of Na2CO3, hydrolysis of carbonate occurs. Primary water (CO3)2-+H2O=HCO3-+OH-, which will release OH- and make the solution alkaline; Secondary water HCO3-+H2O==H2CO3+OH-, which also releases OH-, but the degree of secondary hydrolysis is much smaller than that of primary hydrolysis (negligible). Of course, at this time, the bicarbonate obtained by first-stage hydrolysis will also be ionized to obtain H+, but the first step of the hydrolysis reaction is pure. Secondary hydrolysis and ionization of bicarbonate in particular can be ignored.

Therefore, the Na2CO3 solution is alkaline. It can be seen from the above that the degree of hydrolysis of sodium carbonate and sodium bicarbonate can be reflected by their primary hydrolysis, and the amount and concentration of the hydrolyzed oh- substance can reflect the degree of hydrolysis, that is, the alkalinity of the two can be judged by the amount concentration of the same substance, because the alkalinity of sodium carbonate is much greater than that of sodium bicarbonate at the amount concentration of the same substance, so the degree of hydrolysis of sodium carbonate is greater than that of sodium bicarbonate.

Sodium carbonate is a strong base and weak salt, which is hydrolyzed by the combination of carbonate ions and hydrogen ions ionized from water to form bicarbonate and carbonic acid as an electrolyte.

Sodium carbonate molecular weight. The purity of chemicals is more than 100%, also known as soda ash, but the classification belongs to salt, not alkali. Also known as soda or soda ash in international **.

It is an important organic chemical raw material of Xunhui, mainly used in the production of flat glass, glass products and ceramic glaze. It is also widely used in household washing, acid neutralization, and food processing. Basic chemical raw materials, widely used in medicine, state resistant medical use for excessive gastric acid, Fanchangchun papermaking, metallurgy, glass, textile, dyes and other industries, used as a food industry starter agent.

Categories: Education Academic Exams >> Gaokao.

Problem description: Sodium carbonate hydrolysis.

There is Na+ H+ HCO3- CO3- OH- in the solution, where the ion concentration is high to low, what is the order in which the ion concentration is high to low?

Which is more, HCO3- or H+, in particular?

Analysis: The order is Na+, CO32-, OH-, HCO3-, H+Reason: 1'Sodium carbonate is a strong electrolyte, all ionized, so Na+>CO32-2'CO32- is partially hydrolyzed, mostly still in ionic form.

3' hydrolysis is mainly in the first step, so CO32->HCO3-, HCO3-=OH- in the first step, and at the same time there is ionization of water, so the total OH->HCO3-

4'For high school students, the comparison of HCO3- and OH- in this question is beyond the curriculum.

If you are interested, please refer to the calculation of polyacids and bases in university analytical chemistry.

The chemical equation for sodium percarbonate to be soluble in water is as follows:

When sodium percarbonate is added to water, hydrogen peroxide is rapidly produced, and hydrogen peroxide is unstable, producing oxygen and water. The final sodium carbonate of the reaction, when dried, is a white powder or granule, odorless, and is an alkaline salt. Commonly known as soda, it is not harmful to the human body when eaten, and does not produce heavy metals such as lead and arsenic.

1.What is the chemical formula of sodium percarbonate?

The chemical formula of sodium percarbonate is Na2C2O6

Structural Formula: Na+ [O-Co-O-O-Co-O]2- Na+ Co is a carbonyl group.

Sodium percarbonate crystal chemical formula.

2.What does the aqueous solution of sodium percarbonate react with manganese dioxide? Write the reaction equation.

After decomposition, oxygen, water, and sodium carbonate are produced, which is essentially manganese dioxide-catalyzed hydrogen peroxide decomposition.

When this reaction is over, can the reaction continue if sodium percarbonate is added?

Manganese dioxide is not consumed, so it can continue to react, and even without manganese dioxide sodium percarbonate, it can decompose into sodium bicarbonate and oxygen relatively quickly in water.

The degree of hydrolysis of carbonate is much greater than that of bicarbonate.

kb1=kb2=

Through the above hydrolysis constants, it can be seen that the primary hydrolysis of carbonate is much greater than the secondary hydrolysis degree of bicarbonate.

The degree of hydrolysis of sodium carbonate is large, it has two steps of hydrolysis, and the salt of multiple weak acids is hydrolyzed in steps, the first part is greater than the second step The equation is as follows: CO3 2 - H2O==== (reversible sign) H+ HCO3 - HCO3 - H2O=== (reversible sign) H+ H2CO3