Junior High School Chemistry Topics Acid Base Salt Identification of Substances Special Topic

11. DOH- and NH4+ form gas, and Ba2+ and SO42- generate precipitation.

12. CCO32- and Ca2+ precipitation, CO32- and H+ produce gas.

13. D is similar to 11, OH- and NH4+ produce gases, and Ba2+ and CO32- produce precipitation.

14. CCACO3 precipitation.

15. BCA, CO32- precipitation, phenolphthalein red, identifiable.

D. Phenolphthalein red, the red color disappears after adding HCl, and can be identified.

16. BbA2+ and SO42-, H+ and CO32-

17. CFE(OH)3 brown precipitate, Mg(OH)2 white precipitate.

18. A blue CuSO4 -- produces blue precipitate NaOH --- produces white precipitate BA2+ - white precipitate SO42- -no phenomenon KCl

19. B blue Cu2+--produces blue precipitate (OH-)-white precipitate (Mg2+)-white precipitate (Ba2+)-no phenomenon KCl

20. B yellow-brown Fe3+ - yellow-brown precipitate (OH-) - white precipitate (SO42-) - white precipitate (Ba2+) - no phenomenon KCl

12. Da Fe(OH)3 yellow-brown precipitate.

B CaCO3 white precipitate.

C Cu2+ blue solution.

Good luck with your studies

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Acid: The cation produced during ionization is a compound that is all hydrogen ions, called acid.

Base: The anions produced during ionization are all hydroxide ion compounds, called bases.

Salt: A compound of acid ions and metal ions, called salts.

Example: Acid: H2SO4 (sulfuric acid) HCl (hydrochloric acid) Hno3 (nitric acid) Base: NaOH (sodium hydroxide) KOH (potassium hydroxide) NH4OH (ammonia) Salt: Na2CO3 (sodium carbonate) CuSO4 (copper sulfate) acid-base proton theory.

In order to make up for the shortcomings of Arrhenius's ionization theory, the Danish chemist Brunsti and the British chemist Laurie respectively proposed the acid-base proton theory in 1923. The main points are as follows:

Everything that can give protons is an acid, and everything that can accept a proton is a base.

Acid-base conjugation: acid = base + proton (the stronger the acid, the weaker its conjugate base) Definition of pH: pH = -lg [concentration of hydrogen ions] (proposed by the Danish physiologist Sorensen).

Under this theory, water is both acidic and alkaline.

Acid: cation has and only H+

Base: Anions have and only oh-

Salts: Cations include metal cations (including ammonium NH4+) and above are limited to junior high school only.

Acid: purple litmus turns red, colorless phenolphthalein does not change color, pH 7 alkali: purple litmus turns blue, colorless phenolphthalein turns red, pH 7 salt:

In the case of purple litmus does not change color, in case of colorless phenolphthalein does not change color, pH close to 7ps individual salts are acidic or alkaline, such as basic copper carbonate, acid sodium carbonate, etc., but as long as the component is metal + acid is salt.

.A, B, C, D four reagent bottles respectively contain sodium carbonate, silver nitrate, caustic soda, dilute sulfuric acid four dilute solution of one of the four dilute solutions, take a small amount of each of the four solutions, drop into the solution of substance X and dilute nitric acid in turn, the phenomenon is shown in the following table:

a b c d

x White precipitate White precipitate White precipitate No phenomenon.

Dilute nitric acid, the precipitation does not disappear, the precipitation disappears, there are bubbles, the precipitation disappears, and there is no phenomenon.

Answer: The chemical formula of substance X is , substance B is , the chemical equation of the reaction after adding X is , and the chemical equation of the reaction after adding dilute nitric acid and the disappearance of the precipitate is , in order to further distinguish A and C, you can conduct experiments according to the principle of displacement reaction and write the chemical equation of one of the reactions.

Answer:BaCl2 Sodium carbonate (Na2CO3 or soda ash) Na2CO3 + BACl2 = BaCO3 + 2NaCl

BaCO3+2Hno3=Ba(NO3)2+H2O+CO2 Fe+AGNo3=Fe(NO3)2+2AG (or Fe+H2SO4=FeSO4+H2).

1) There are colored gases in the gas storage bag, which may be several gases such as NO2 CH4 CO2 HCL NH3 BR2 vapor, and the following operations are carried out: 1 pass a little in water to obtain a colorless solution; 2 pass a little in agno3 solution, there is precipitation; 3. Pass a little in the clarified lime water, no turbidity; 4 Through the gas washing cylinder filled with water, the exported gas is then passed into the clarified lime water, resulting in turbidity, then: it can be judged from 1 that there must be no existence

From 2 can be judged, there must be there must not be From 3 and 4, it can be judged that there must be and may exist

2) Let x, y, and z represent the three elements between 1 and 20. Known.

1,x( ) and y(-) have the same electron shell structure;

2. The number of protons in the nucleus of element z is 9 less than that in the nucleus of element y.

Two elements, 3, y, and z, can form a negative monovalent anion with 4 cores and 42 electrons.

Fill in the blank: (1) Element y is element z 2) The chemical formula of a 60-electron salt compound formed from the elements x, y, and z is

It is known that A, B, and I are all elemental, in which A burns in the air and emits dazzling white light to form a white solid C, and substances A, C, F, all contain the same certain element, and B, D, and I are all colorless and odorless gases. Some of the reactions between these substances are shown in the reaction expressions below (reaction conditions are omitted).

a b→c ②a h→f i↑ ③c h→f e ④g h→f e d↑ ⑤b i→e ⑥e→b↑ i↑

1) The chemical formula of a substance is: ;

2) Write the chemical formula of another substance that is the same as the constituent element of the E substance: ;

3) Write the chemical equation for d to be converted to b under certain conditions: ;

4) A and D can have a displacement reaction under high temperature conditions, and the chemical equation of the reaction is written.

1. Add purple litmus test solution to distinguish acid and alkali, and sodium chloride does not change color.

2. Sulfuric acid is added to the (alkali) that turns the test solution blue, and the precipitate is barium hydroxide, and sodium hydroxide is generated without precipitation.

3. Silver nitrate is added to the (acid) that turns the test solution red, and the white precipitate is hydrochloric acid.

Equation: barium hydroxide plus sulfuric acid: Ba(OH)2 + H2SO4 ====BAso4 + 2H2O

Sodium hydroxide plus sulfuric acid: H2SO42NaOH

na2so4

2H2O hydrochloric acid plus silver nitrate: HCLagNO3

agcl↓hno3

Sulfuric acid plus silver nitrate does not react.

1.Precipitation. (caco3, etc.).

2.Weak electrolytes are like: water, weak acids and weak bases: including carboxylic acids (organic acids, such as acetic acid), hypochlorous acid, ammonia, etc.

3.Occurs after the exchange of ions produced by gases (unstable substances): carbonic acid, sulfurous acid, hydrosulfuric acid, ammonia. CO2 is generated separately

so2h2s

nh34。Redox reactions.

Correct the mistake upstairs" with SO42

The compound is only BaSO4

insoluble in water, everything else is soluble in water".

Among them, calcium sulfate is good, silver sulfate is a slightly soluble, when it is a product, it can be treated as a precipitate, when it is a reactant, it can be treated as a soluble, and it can be disassembled when writing the ion equation (except for the emulsion).

One. You can see the solubility table at the end of the textbook.

Two. Specific:

1. Solubility of salt.

Substances containing potassium, sodium, nitrate, and ammonium are all soluble in water.

Only AgCl is insoluble in water, and the others are soluble in water;

Contains SO42

The compound is only BaSO4

insoluble in water, everything else is soluble in water".

Contains CO32

Only K2CO3, Na2CO3 and (NH4)2CO3 are soluble in water, and the others are insoluble in water.

2. Solubility of alkali.

The alkalis soluble in water are: barium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydroxide and ammonia, and other alkalis are insoluble in water. Fe(OH)3 is a reddish-brown precipitate, Cu(OH)2 is a blue precipitate, and other insoluble bases are white. (including Fe(OH)2).

Note: AGCL and BaSO4 in the pellet

Insoluble in dilute nitric acid, other precipitates can be soluble in acid. Such as: mg(OH)2

caco3baco3

ag2co3

3. Silicic acid is insoluble, and other acids are soluble.

4. Most acids and acidic oxides are soluble in water, (acidic oxide water acid) most alkaline oxides are insoluble in water, and soluble are: barium oxide, potassium oxide, calcium oxide, sodium oxide (alkaline oxide water alkali).

Acidic salts: salts (soluble) containing Fe3+, Cu2+, Fe2+, NH4+, etc., are hydrolyzed (who is weak and who is hydrolyzed) is acidic.

NahsoThese are double salts that can be completely ionized.

Basic salts: Na2CO3, K2CO3, the principle is the same as above.

Strong acids: triacids (salt, nitrate, sulfur).

Weak acids: carbonic acid, phosphoric acid, acetic acid, silicic acid (insoluble).

Strong bases: KOH, Naoh, BA(OH)2, etc. (must be soluble Ca(OH)2 is also (can be completely ionized, if possible, it can be measured with test strips), usually containing alkaline earth metals and alkali metal ions (on the first two columns of the periodic table)).

Weak alkali: ammonia monohydrate (not ammonia).

Acid: HCLh2SO4

Base: Naoh

ca(oh)2

Salt: Na2CO3

nahco3

This is actually the most common test for NACL.

Oxide: CAO

fe2o3h2o2

h2oco2