What is the basis for the difference between acids and alkalis?

Acid: refers to the cation that is completely hydrogen ion when ionized in solution.

Base: A general term for hydroxide-containing compounds.

Salts: Compounds composed of metal ions (or ammonium ions NH4+) and acid ions.

The above explanation is more comprehensive, and the popular point is that the one that starts with h is acid, the one that ends with oh is alkali, and the one that starts with not h and ends with oh is salt. Of course, this statement is only a necessary condition and should not be judged in this way. However, this method is effective for most compounds at the junior high school level.

But if you want to get a high score, you have to judge it in the same way as at the beginning, and you have to understand the concept of ions.

Acids can only ionize H+

Bases can only ionize oh-

Neutral ones, on the other hand, may ionize protons, but can also ionize other ions.

In terms of chemical formula:

Acid: hydrogen ion + acid ion Commonly used H2SO4 HCl base: metal ion + hydroxide ion Commonly used Ca(OH)2 NaOH [ammonia NH3·H2O is also a base].

Salt: metal ion + acid ion commonly used FeCl3 CuSO4, etc. ["Caustic soda" is not alkali, most salt solutions are neutral, but some are acidic, alkaline, and others are not confused: such as NaHCO3 and NaCl are also salts].

From the name: acid: x acid.

Base: Hydroxide X

Salt: X-Acid X or X-Acid

Don't feel too dizzy, just master the rules and practice the differences.

Acid: gives proton (h+).

Base: Accepts protons.

The method of distinguishing acid-base salts: the compound with all cations H+ is an acid, the compound with an all-oh- anion is a base, and the compound composed of metal ions and acid ions is a salt.

Acids are also acids in compounds that produce all cations (H+) during ionization, or substances that dissolve in water and release protons to form H3O+ (hydronium ions). The higher the concentration of H3O+, the more acidic the solution becomes.

In the theory of acid-base ionization, alkali refers to the compound that ionizes anions in aqueous solution, all of which are OH-; In acid-base proton theory, a base refers to a compound that can accept protons; In acid-base electron theory, a base refers to an electron donor.

In chemistry, salt refers to a class of metal ions or ammonium ions (NH) combined with acid ions of compounds, such as calcium sulfate, copper chloride, sodium acetate, generally speaking, salt is the product of metathesis reaction, such as sulfuric acid and sodium hydroxide to produce sodium sulfate and water, there are also other reactions to form salt.

The narrow definition of acid in chemistry is: the cations ionized in an aqueous solution are all hydrogen ion compounds. Proposed by Arrhenius, this theory is known as Arrhenius' acid-base theory.

Broadly defined: a substance capable of accepting electron pairs.

Most of these substances are soluble in water, and a small part, such as silicic acid, is insoluble in water. An aqueous solution of an acid generally conducts electricity, and its conductive properties are related to its degree of ionization in water.

Some acids exist in the form of molecules in water and do not conduct electricity; Some acids dissociate into positive and negative ions in water, which can conduct electricity.

1. The compound with all cations H+ is acid, the compound with all anions is oh- is alkali, and the compound composed of metal ions and acid ions is salt.

2. Acid: A compound that is composed of all hydrogen ions (H+) generated during ionization is called an acid, or a substance that dissolves in water and can release protons to form H3O+ (hydronium ion) is also an acid. Such as hydrochloric acid, sulfuric acid, carbonic acid, nitric acid, etc.

Universality of acids: acid solution can react with acid-base indicators, acid + alkaline oxide = salt + water, etc.

3. Alkali: The anions ionized in the aqueous solution are all oh-, and the substance is a base. Such as lithium hydroxide, sodium hydroxide, rubidium hydroxide, cesium hydroxide, francium hydroxide, etc.

Universality of alkali: the alkali solution can react with the acid-base indicator, the purple litmus test solution turns blue when it encounters alkali, and the colorless phenolphthalein test solution turns red when it encounters alkali.

4. Salt: Compounds in which metal ions or ammonium ions (NH4+) are combined with acid ions or non-metal ions are salts. Such as sodium chloride, calcium nitrate, ferrous sulfate and ammonium acetate, calcium sulfate, copper chloride, sodium acetate, etc.

Salt generality: some salts are weakly corrosive, and the pH of the solution is judged according to the properties of the salt, which can react with certain acids, alkalis, salts, and other compounds.

The cations are only H+, and they are all acids.

Anions are only oh-, and they are all bases.

Salt, in addition to acid and alkali, and then remove organic matter (like methane, ethylene, acetylene, benzene, toluene, acetaldehyde, etc.) compounds are all salts No matter what it carries, cations have both H+ and other cations (such as K+, etc.) are acid salts.

1. Definition of acid:

Chemically, it refers to compounds that are hydrogen ions when the cations are ionized in an aqueous solution.

2. Definition of alkali:

Base refers to a substance that ionizes anions in an aqueous solution and is all OH-; In acid-base proton theory, a base refers to a substance that can accept protons; In acid-base electron theory, a base refers to an electron donor.

3. Definition of salt:

Salts refer to a class of compounds in which metal ions or ammonium ions (NH4+) are combined with acid ions or non-metal ions.

Sour:It is composed of hydrogen ions (H+) and acid anions, such as HCl, H2SO4

Alkali:It is composed of hydroxide ions (OH-) and metal cations, such as NaOH and KOH

Salt:It is composed of metal cations or ammonium ions (NH4+) and acid anions, such as NaCl, NH4Cl

Sour:The cations produced when ionized in an aqueous solution are all compounds of hydrogen ions (H+);

Alkali:The anions ionized in the aqueous solution are all hydroxide ion (OH-) compounds;

In acid-base proton theory, a base refers to a substance that is capable of accepting protons; In acid-base electron theory, base refers to electron donor. ）

Salt:Refers to a compound consisting of metal ions or ammonium ions (NH4+) combined with acid ions or non-metal ions.

Chemical properties of acid-base salts.

Sour:

1) It can react with acid-base indicator, purple litmus test solution turns red when it is acid, and colorless phenolphthalein test solution does not change color when it meets acid;

2) It can react with multi-excitation retardation of active metals, usually to produce salts and hydrogen. Only metals that precede hydrogen in the order table of metal activity can react with dilute acids to produce hydrogen. Metals located after hydrogen cannot react with dilute acids, but can react with oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid;

3) It can react with alkaline oxides to form salts and water;

4) It can react with certain salts to form new acids and new salts;

5) It can neutralize with alkali to form salt and water.

Alkali:

1) Neutralization reaction with acid;

2) reacts with certain non-metallic oxides;

3) Turns purple litmus blue; reddens colorless phenolphthalein;

4) It can react with certain salts to form new salts and new alkalis.

Salt:

1) Displacement reaction: In the order of metal activity, only the metals in front can be replaced from their salt solution;

2) react with certain metals to generally form another salt and another metal;

3) It can react with acid to generally form another salt and another acid;

4) It can react with alkali to generally form another salt and another alkali;

5) It can react with another salt, generally to produce two other salts.