Why does the addition of electrolytes destroy the sol and make the sol coalescing

Because colloidal particles have a large specific surface area and strong adsorption capacity, they often adsorb a certain charge, so the phenomenon is that colloidal particles repel each other and are suspended. The addition of electrolytes disrupts the original equilibrium, increasing the chance of collision between colloidal particles, agglomerating into large particles and weakening their repulsion from each other, thus accumulating and sinking.

The surface of the sol adsorbs a lot of ions, with the same charge and repels each other, adding electrolyte will make the ion charge adsorbed on the surface be neutralized, so the electrolyte will destroy the sol and make the sol coalesce.

The principle is to neutralize the charge of the particles or to speed up the thermal movement of the particles to increase the chance of binding of the particles.

The addition of electrolyte to the solution increases the total concentration of ions in the colloid, and creates favorable conditions for the charged colloidal particles to attract oppositely charged ions, thereby reducing or neutralizing the charge of the original colloidal particles, so that they lose the factor of maintaining stability. At this time, due to the Brownian motion of the particles, when they collide with each other, they can gather and settle rapidly.

When salts (electrolytes) are added to colloids, cations or anions can neutralize the charge of dispersed particles, causing the disperses to aggregate into larger particles and form precipitates under the action of gravity. This phenomenon of colloidal formation and precipitation is called colloidal polyprecipitation (applicable to liquidsols).

Extended information: Brine and gypsum can "order" tofu, and in the same way, other electrolytes, such as table salt, brewed white vinegar, etc., can also "order" tofu. However, using salt to "order" tofu is generally inedible due to its salty taste.

For the first time, brewed white vinegar is used, and later it can be fermented with the slurry water leached from the tofu to "order" the tofu, and such tofu is called sour tofu. Sour tofu does not have any additives and chemicals, it can be said that "the original soup is the original food", and it is the best green tofu.

In life, alum water purification also uses the principle of "colloidal aggregation and sedimentation". The scientific name of alum is potassium aluminum sulfate dodecahydrate, which will form a positively charged aluminum hydroxide colloidal when dissolved in water, and the fine dust particles in the sediment are dispersed in the water in colloidal form because of their small particle size and small specific gravity.

Dust particles colloids generally have a negative charge, and when the two meet, they can neutralize the negative charge carried by the sediment colloid, and the accumulation and precipitation occur, so that the turbid muddy water becomes very clear. Alum water purification was often used in rural and field expeditions in the past.

The main reason why colloids have greater stability is that the colloids have an electric charge, and generally the same kind of colloids have the same charge, so they repel each other, preventing them from approaching each other, so that it is difficult for the colloids to gather into larger particles and settle. In addition, both potential ions and counterions in the adsorption layer can be hydrated, thus forming a hydration layer around the colloidal particles, which prevents the aggregation between the colloidal particles and prevents the combination of the colloidal particles and the oppositely charged ions, so that the colloidal solution is dynamically stable.

There are many ways to make colloidal aggregation and sedimentation, mainly including: (1) adding a small amount of electrolyte to increase the total concentration of ions in the colloidal solution, so that the charged colloidal particles are easy to attract oppositely charged ions, so as to eliminate the repulsion of colloidal particles with the same charge, and the colloidal particles can collide with each other, which is conducive to aggregation and sedimentation. For example, FeO+ ions are adsorbed on the surface of Fe(OH)3 cores, and the counterions in the diffusion electric double layer are mainly Cl-, and when Na2SO4 is added, SO42- can also enter the adsorption layer, which reduces the charge of the colloids and makes them easy to coalesce and settle.

2) Two colloidal solutions with opposite nuclear pure charges, mixed in an appropriate proportion, can be electrically neutralized with each other, and polyprecipitation occurs. For example, alum purified water, Al(OH)3 sol and negatively charged colloidal impurities in natural water are neutralized and precipitated with each other. (3) Heating can promote colloidal sedimentation.

Because the heating can increase the movement speed of the rubber particles, thus increasing the chance of colliding with the particles, and also reducing the adsorption effect of the glue nucleus on ions, so that the colloids can accumulate and settle when they collide. For example, Fe(OH)3 colloids can be precipitated by heating.

1.Add electrolytes.

2.Mutual aggregation and sedimentation of sols.

3.The role of macromolecular compounds.

The anions and anions contained in the electrolyte neutralize the electrically charged particles adsorbed by the colloidal particles, resulting in the colloidal particles no longer repelling each other due to the same charge when they collide, and the colloidal particles become larger and larger when they collide, and finally precipitate under the action of gravity.

Electrolytes are added. The addition of electrolyte to the colloidal increases the concentration of particles in the colloid, which is contrary to the electrical properties of the colloidal particles, and creates favorable conditions for the charged colloidal particles to attract oppositely charged ions, thereby reducing or neutralizing the charge of the original colloidal particles, so that they lose the factor of maintaining stability. At this time, due to the Brownian motion of the particles, when they collide with each other, they can be gathered.

Settle quickly.

According to the DLVO theory, there are two forces acting between the sol colloidal particles. One is van der Waals gravitational force and the other is electrostatic repulsion (colloidal particles with the same charge). If the gravitational force is greater than the repulsive force, the colloids will accumulate and settle and cannot exist stably; If the repulsive force is greater than the gravitational force, the colloids can be stable in existence.

When electrolytes are added, the electrolyte has little effect on van der Waals forces, but it reduces the repulsion between the colloids. If the repulsion is reduced to less than the gravitational force, the colloidal aggregates and sinks.

The higher the valence of the counterion, the greater the aggregation and sedimentation capacity. The higher the valence of the same ion, the smaller the accumulation and sinking capacity, Schultz-Hardy rule: the aggregation and sinking value is inversely proportional to the sixth power of the heterogeneous ion charge, that is, the higher the charge, the smaller the aggregation and sinking value, and the stronger the aggregation and sinking ability!

A. AgNO3 is excessive, and the AGI particles in the obtained AGI colloid are positively charged.

Anions act as follows: poly-precipitation capacity [Fe(CN)6]3->SO42- >Cl- i.e., K3[Fe(CN)6] > MgSO4 >Al Cl3B, Ki excess.

The AGI particles in the obtained AGI colloid are negatively charged, so the cation acts: the aggregation and precipitation capacity Al3+ > Mg2+ >K+ i.e., Al Cl3 > MgSO4 >K3[Fe(CN)6].

The greater the accumulation and sinking value of the electrolyte to the sol, the smaller its accumulation and sinking capacity.

Causes of colloidal stability:

The colloids have some kind of same charge to repel each other, and the irregular thermal movement between the particles also makes the pellets stable.

Therefore, to make the colloidal agglomeration, the principle is as follows: neutralize the charge of the colloid, accelerate the thermal movement of the colloidal particles to increase the binding opportunity of the colloids, so that the colloids aggregate and precipitate.

According to Schultz Hardy's rule.

The accumulation and sedimentation capacity is inversely proportional to the sixth power of the valence of heteroelectric ions.

The smaller the hydration radius, the stronger the aggregation and sinking capacity of the same valence number.

The higher the coionic valence, the smaller the aggregation and sedimentation capacity. The higher the valence of the counterion, the greater the aggregation and sedimentation capacity.

The addition of electrolyte to the solution increases the total concentration of ions in the colloid, and creates favorable conditions for the charged colloidal particles to attract oppositely charged ions, thereby reducing or neutralizing the charge of the original colloidal particles, and the masking makes them lose the factor of maintaining stability. This is due to the Brownian motion of the particles.

When they collide with each other, they can gather together and settle quickly.

When salts are added to the colloid, the cations in it.

Or anions can neutralize the charge carried by the dispersed particles, so that the dispersed particles can gather into larger particles, which form precipitate under the action of gravity. This phenomenon of colloidal formation and precipitation is called colloidal precipitation.

suitable for liquidsols).

For example, when making tofu from soy milk, at a certain temperature, caSO4 (or other electrolyte solutions) is added, and the charge of the colloidal particles in the soy milk is neutralized, and the particles in it quickly gather to form jelly-like tofu (called gel). Fast and fierce.

The reason for the addition of a small amount of electrolyte nanoosmosis causes the sol to coalesce and sink ()aChanges in the adsorption layer by electrolyte ions.

b.The electrolyte adsorbs the solvent.

c.The electrolytic bureau forms an ionic atmosphere or ion-paired.

d.The charge of the colloids is increased.

e.Inhibited Brownian motion.

f.Neutralizes the charge carried by the particles.

Correct Answer: Change of electrolyte ions on the adsorption layer; Neutralizes the charge carried by the ridge grains of the rubber hole.