Neutralization of primary three acids and bases

A: You can't use litmus. When the amount of acid added is the same as that of the alkali, the phenolphthalein fades, which is better than the litmus, which turns red from purple to our naked eye, and is not sensitive to its color change.

Yes, but litmus turns red when it encounters acid and turns blue when it encounters alkali In actual operation, the phenomenon is not obvious, and there is no phenolphthalein from colorless to redden.

Because the actual color of litmus is purple, it changes to blue, which is less obvious. And phenolphthalein will only meet reddening, which is better. What does the actual case mean, phenolphthalein can test paper mill wastewater, test soil acidity and alkalinity.

No, because the actual color change of litmus is less obvious, and it doesn't happen to be a complete reflection of the control, what is the actual case?

The discoloration range of phenolphthalein is 8-10 and the color is developed in the alkali, and it will fade after adding acid to neutralize, and the color change is obviously easy to observe, while the discoloration range of litmus is acidic, which requires excessive calculation, and the error is greatly increased, so it can not be used.

Yes, but use a purple litmus solution, which turns blue when exposed to alkali and red when exposed to acid; Phenolphthalein turns red when exposed to alkali and does not change color when exposed to acid, but phenolphthalein cannot distinguish between acidic and neutral.

Generally speaking, there is nothing wrong with using litmus in theory, but its color change is not obvious, which is easy to cause errors in titration.

Because phenolphthalein turns blue when it meets alkali and turns red when it meets acid, it can judge the acidity and alkalinity of sodium hydroxide by the change of the color of the indicator, of course, you can use litmus Because litmus turns red when it meets alkali and does not change color when it encounters acid, it can also distinguish acid-base solutions.

NaOH is a base, it will be litmus turning blue, blue is close to litmus Bunsen color, purple is relatively similar, the effect is not obvious, so phenolphthalein is used.

No, the red color that appears will fade.

Because the measurability of litmus is limited, plus its changes are not obvious

The neutralization reaction of acids and bases is the reaction in which acids and bases react to produce salts and water.

In the reaction of strong acid and strong base, there is generally no obvious experimental phenomenon (precipitation, bubbles, dissolution of insoluble matter, change of solution color), so in order to observe whether the reaction is high or not, it is necessary to use acid-base indicators. Hydrated lime improves acidic soils (in the absence of hydrated lime, quicklime can also be used), and carbonated water improves alkaline soils.

Add sodium hydroxide solution to the beaker, drop a few drops of phenolphthalein solution, slowly drop dilute hydrochloric acid with a dropper, and constantly stir with a glass rod (if the container is a test tube, shake directly), when the solution has just faded from red to colorless, it means that sodium hydroxide and hydrochloric acid happen to react completely.

Application of acid-base neutralization reaction

1. Alleviate soil acidification.

Acidic soils have low nutrient availability, so plants cannot grow properly, and deforestation, for example, is one of the world's most striking ecological crises, in large part due to soil acidification. With hydrated lime, a neutralization reaction with acid can solve this problem.

2. Production of hydrated lime.

Hydrated lime is convenient and cheap, and the solubility of hydrated lime is small, so the damage to the soil and plants is small, and it can also provide some inorganic salt calcium elements for plants to promote the growth of plant cell walls.

3. Remove limescale.

After the kettle is used for a long time, you will find that there is white scale on the inner tank, that is, scale, and continue to use such a kettle for a long time, which will not only waste power resources, but also harm the human body if you drink it for a long time, and you can easily solve this problem by using vinegar at home.

Neutralization is a reaction in which acids and bases exchange components with each other to form salts and water (acid + alkali salt + water). Its essence is the combination of H+ (hydrogen ions) and OH- (hydroxide ions) to form water. In a neutralization reaction, a complete neutralization reaction is when the acid-base happens to be completely reacting.

In practical production applications, people often use neutralization reactions to improve soil acidity and alkalinity, excessive gastric acid, and treat wastewater.

Reaction principleAcids and bases are ionized into freely moving anions and cations after being dissolved in water. For example, HCL (hydrochloric acid) is ionized into hydrogen ions (H+) and chloride ions (Cl-), while NaOH (caustic soda) is ionized into sodium ions (Na+) and hydroxide ions (OH-).

Hydrogen ions and hydroxide ions combine to form water that is extremely difficult to ionize, so what is left in the solution are sodium ions and chloride ions. Sodium and chloride ions are still ionized in solution and do not combine. But the product is NaCl (salt).

Therefore, the essence of the neutralization reaction is the reaction between acid and alkali to produce salt and water.

,naoh，na2co3(

Ca(OH)2 is not excessive, Ca(OH) (excessive), CaCO3

2.There is also ca(oh)2

3.The first one doesn't know which overdose, if it's HCL overdose, it's colorless, if it's NaOH overdose, it's red.

The second is indistinguishable.

The third has a white precipitate generated.

4.It may be to analyze any changes in color, smell, etc., or not to dump waste liquid.

First, the first reaction: NaCl, Naoh, phenolphthalein (no obvious change) or NaCl, HCl phenolphthalein (reddening) The second reaction: Na2CO3, NaOH or; Na2CO3, NaHCO3 (no obvious phenomenon).

The third reaction: CaCO3 is generated anyway, phenomenon: white flocculent precipitate is generated.

2. Sodium carbonate, sodium hydroxide or sodium carbonate, sodium bicarbonate. We all know that alkali can make phenolphthalein red, and sodium carbonate and sodium bicarbonate undergo a hydrolysis reaction in water to produce carbonic acid and sodium hydroxide, so he can also make phenolphthalein red.

Three, the first reaction does not know which overdose, if the HCL is overdose, it is colorless, if the NAOH is overdose, it is red.

The second reaction was insignificant.

The third reaction has a white precipitate formation.

Fourth, it is also necessary to consider the amount of reactants (the question of appropriate amount and excess).

Neutralization reaction: A reaction in which acids and bases interact to form salts and water.