When sodium is added to pure water, how does the degree of ionization of water change and why

Water is a weak electrolyte, and when sodium reacts with water to form sodium hydroxide and hydrogen gas, the oh- in the water increases, so where does the oh- come from, of course, it is produced by the ionization of water. However, the ionization of water also needs to reach a corresponding equilibrium, so the concentration of H+ also increases accordingly. In this process, due to the continuous reaction of H+ to form H2, the concentration of H+ decreases, and the whole solution is alkaline.

It's getting smaller. na + h2o --naoh + h2|As the concentration of OH- increases, the concentration of H+ decreases.

The H+ concentration indicates the degree of ionization of water. Because H+ can only be ionized by water, the ionization of H2O decreases.

Addendum: Yes, grasp the main factor.

Intensifier. Actually, it's not a contradiction. 2na +2h2o --2naoh + h2

The addition of sodium promotes the ionization of water, producing H+ and OH-, and the solution is alkaline as a whole due to the conversion of H+ into gas overflow.

At the same time, the concentration of hydroxide ions is increased, which inhibits the ionization of water. It is precisely because of these two processes that a balance can be achieved.

When alkali dissolves in water, how much does it affect the ionization of water? Very little.

For example, the ionization of water at 50 degrees or water at 25 degrees is obviously better. Small.

The amount of water, in real terms, is very large, after the lye reaches saturated solubility, for countless water molecules, affecting its ionization, can not be considered.

Once you want to consider the impact of this aspect, it is also a relatively remote problem and can be used as a competition question.

H2O <==>H+ +OH-, very weak electrolyte.

When Na is added, this equilibrium is broken, Na + 2H+ -H2 + Na+ In this way, the neutrality of the water is broken and such a reaction formula is formed.

na + h2o --naoh + h2

I'm sure you'll write the ionization equation, and it's not that hard, isn't it?

Don't look at the problem, just look at the score.

Capture the main influencing factors.

That's because water ionization produces hydrogen ions, and the reaction of sodium metal with hydrogen ions consumes the hydrogen ionization and promotes the ionization of water.

When a sodium block is dropped into the water, the following phenomena can be observed:

1. The sodium block floats on the surface of the water. This is due to the fact that sodium is less dense than water;

2. Sodium immediately reacts with water, and gas is produced. This is due to the fact that sodium is chemically reactive and reacts with water to produce hydrogen;

3. Sodium metal melts into small balls. This is due to the relatively low melting point of sodium, and the heat released by the reaction of sodium and water can melt sodium;

4. The small round ball swims rapidly in all directions on the water surface, which is due to the gas produced to push the sodium block to move;

5. There is a hissing sound, and finally the small ball disappears. The sound is caused by two reasons for the abrasion of the surface: one is the burst of the bubble that produces gas; The second is the bursting of the bubbles of water vapor produced by exothermic water near the boiling point of the sodium block.

6. The aqueous solution after the reaction turns the phenolphthalein indicator red. This is due to the formation of alkali by the reaction.

That's because water ionization produces hydrogen ions, and the reaction of sodium metal with hydrogen ions consumes the hydrogen ions, promoting the ionization of water.

When a sodium block is dropped into the water, the following phenomena can be observed:

1. The sodium block floats on the surface of the water. This is due to the fact that sodium is less dense than water;

2. Sodium immediately reacts with water, and gas is produced. This is due to the fact that the chemical properties of sodium are very active, and it reacts with water to form hydrogen;

3. Sodium metal melts into small balls. This is due to the relatively low melting point of sodium, and the heat released by the reaction of sodium and water can melt sodium;

4. The small round ball swims rapidly in all directions on the water surface, which is due to the gas produced to push the sodium block to move; Clear the trap.

5. There is a hissing sound, and finally the small ball disappears. The sound is caused by two reasons: first, the bursting sound of bubbles that produce gas; the second is the bursting sound of the bubbles of water vapor produced by exothermic water near the boiling point of the sodium block;

6. The aqueous solution after the reaction turns the phenolphthalein indicator red. This is due to the formation of alkali by the reaction.

Because the essence of the reaction between sodium and water is the reaction of hydrogen ions produced by the ionization of sodium and water. The equation is:

When sodium reacts with hydrogen ions, the concentration of hydrogen ions decreases; The ionization equilibrium of water shifts to the right, so the addition of sodium promotes the ionization of water. Water is a amphoteric substance that releases and accepts both Michao protons. Water is also weakly dissociated to some extent, and protons are transferred from one water molecule to another.

Ionization equation for water:

h20 = h+ +oh-

The metal Na can react with H+, consume H+, and promote the positive movement of the equilibrium, that is, promote the ionization of water.

When NaOH is added, there is a new OH- that moves the equilibrium in reverse, i.e., hinders the ionization of water.

In fact, the final result is similar, and the aqueous solution of NaOH is obtained.

It's just that Shanheng theoretically rents only bonds, and most of the OH-in the final solution is thought to be produced by water ionization, while the latter is considered to be OH-introduced by NAOH

It's a reaction with the hydrogen ions ionized by water, otherwise you will have hydrogen ions. H2O=H++OH- Now H+ is less water, it is definitely much more ionized.

In the solution, it is an ionic reaction, sodium is added, and the hydrogen ion in the water reacts, the hydrogen ion is reduced, and the ionization balance of the water is shifted to the right, which promotes the ionization of water.

"After adding sodium to the water"with"After getting sodium hydroxide"It's a different concept.

After the addition of sodium, the concentration of hydrogen ions in the water decreases due to the action of sodium and hydrogen ions, thereby promoting the ionization of water. Balance shift right.

Because there is H gas emitted H ions to reduce the ionization of water.

The ionization equilibrium constant (kw) of water is the ratio between the product of the concentration of the product of the dissociation reaction and the product of the concentration of the reactant during the spontaneous ionization of water molecules into hydrogen ions (H+) and hydroxide ions (OH-) under certain conditions. In the standard state, the ionization equilibrium constant kw of water is equal to 10 -14.

However, when it comes to concentrated solutions, other ions (such as Na+, Cl-, etc.) will interact with water molecules, which will affect the tendency and rate of the water dissociation reaction. These ions can form hydrogen bonds and hydroxide ion coordination with water molecules, and can regulate the ionization and solubility of water molecules, thus affecting the ionization equilibrium constant kw of water.

In addition, the activity coefficients of the various ions in the concentrated solution also affect the value of the ionization equilibrium constant kw. The activity coefficient is the ratio of the actual concentration of an ion in solution to the theoretical concentration (i.e., the concentration under ideal conditions). In concentrated solutions, both the interaction between ions and the interaction of ions with solvent molecules affect the behavior of the ions, resulting in a decrease in the activity coefficient.

Therefore, in concentrated solutions, the actual value of the ionization equilibrium constant kw may deviate from its standard value and need to be corrected.

In summary, although the ionization equilibrium constant kw of water is a basic chemical parameter, it is only suitable for pure water systems under standard conditions, not for concentrated solutions. In the case of concentrated solutions, the influence of other factors needs to be considered.