Solutions that can make phenolphthalein solutions reddened are alkaline. What if you add red ink to

The acid-base indicator is mostly an organic weak acid or weak base, and after the pH value of the solution changes, the structure of the indicator changes, and the color changes. The statement in the title is incorrect, it should be said: after the solution is alkaline, the structure of the phenolphthalein indicator changes, causing the phenolphthalein indicator to change from colorless to red; Add red ink dropwise to the phenolphthalein solution to turn red, showing the color of red ink, not the discoloration of phenolphthalein indicator; It is not necessarily an alkaline solution that can turn the phenolphthalein indicator solution red.

First of all, I would like to say that we learned in junior high school and high school that "the solution that can make the phenolphthalein solution red is alkaline", but in fact, this sentence is wrong. In analytical chemistry, phenolphthalein cannot identify the basic substances between them at room temperature, and it is still colorless. And with the change of temperature, the ion product of water will change, and phenolphthalein cannot distinguish acid and base, for example, if you say that a solution of 80 degrees even if phenolphthalein changes color, the solution may be an acid.

Mastery is not required at this stage, this is knowledge later)

Secondly, the landlord said that the solution that can make the phenolphthalein solution red is alkaline, note: it is a substance that makes the redden. If you add red ink to it, this is not the phenolphthalein solution turning red, but the color of the substance added, which cannot be used as a basis for judgment.

Phenolphthalein alkaline condition reddening is the formation of a structure similar to quinone, the solution that can make the phenolphthalein solution reddened is alkaline, this sentence should be the law summarized by the high school chemistry teacher, if the red ink turns red, of course, it cannot be said that the ink is alkaline, because he does not make the phenol itself show red. This statement is not very rigorous in the first place, don't chew on the words.

It is not necessarily a base that can make phenolphthalein red, but an alkaline solution, and in addition to alkali, alkaline solution may also be an alkaline salt.

1. Alkaline solution, such as sodium hydroxide, calcium hydroxide, etc.

2. Strong alkali and weak salt solution, such as sodium carbonate, potassium carbonate, etc.

All alkaline solutions can make phenolphthalein red, so in addition to alkaline solutions, there are some salts that are alkaline in water, which can also make phenolphthalein red, such as sodium carbonate and potassium carbonate, its solutions are alkaline, which can make phenolphthalein red.

The solution that turns phenolphthalein red is alkaline, which can be alkaline or alkaline.

As a commonly used acid-base indicator, phenolphthalein is widely used in acid-base titration processes. Under normal circumstances, phenolphthalein does not change color when exposed to acid solution, does not change color when exposed to neutral solution, and turns red when exposed to alkali solution.

Therefore, it is alkaline.

Which particles in the alkaline solution make the phenolphthalein solution red.

The reaction between sodium peroxide and phenolphthalein reagent is actually a reaction between sodium peroxide and water to produce sodium hydroxide and hydrogen peroxide, which turn red first and then fade. It is hydrogen peroxide that causes phenolphthalein to fade. 1. The specific reaction process of sodium peroxide and phenolphthalein reagent.

2h2o2＝h2o＋o2。Because H2O2 is easy to decompose and crack the mu, it is generally written that the two equations are combined: phenolphthalein is added dropwise to the solution after the reaction, and the color of the phenolphthalein is due to the oxidation of phenolphthalein by H2O2, which destroys the molecular structure of phenolphthalein, so it fades.

Not necessarily. The discoloration of colorless phenolphthalein only requires the pH of the aqueous solution to reach more than 8. Not only alkali, but also many aqueous solutions of strong alkali and weak salts can reach the above value, such as sodium carbonate, potassium sulfide, sodium metaaluminate, sodium silicate and so on.

Phenolphthalein is widely used in the acid-base titration process, usually phenolphthalein does not change color when exposed to acid solution, does not change color when exposed to neutral solution, and turns red when exposed to alkali solution.

Physical properties: phenolphthalein is a white or slightly yellowish crystalline powder, odorless and tasteless. Density.

Melting Point 257-259. It is insoluble in cold water and dissolves more when heated. Soluble in ethanol and ether.

Soluble in caustic solution or alkali metal carbonate solution.

Chemical properties: soluble in caustic solution or alkali metal carbonate solution and react with them to appear red. When acidified, it becomes colorless. In the concentrated alkaline solution, it is also colorless due to the formation of trisodium salt.

Not necessarily, it can also be some alkaline salt solution, such as sodium carbonate, potassium carbonate, sodium bicarbonate, etc.

It is also possible that it is an alkaline salt because its hydrolysis is alkaline.

Phenolphthalein changes color when exposed to alkali and remains unchanged when exposed to acid.

Not necessarily, alkaline is fine.

When phenolphthalein solution is added dropwise to sodium hydroxide solution, the solution turns red.

The purple litmus solution turns red when it is acidic and blue when it is alkaline;

The colorless phenolphthalein test solution does not change color when it encounters an acidic solution, and turns red when it encounters an alkaline solution.

The sodium hydroxide solution is an alkaline solution, and the alkali solution can make phenolphthalein red.

Phenolphthalein is an organic weak acid, which forms colorless molecules in acidic solution, when the concentration is high, but with the decrease of H+ concentration in the solution and the increase of OH- concentration, the structure of phenolphthalein changes, and is further ionized into red ions.