In a chemistry activity class, a student studied a mixture containing two white solids

Solution: a: synthesis steps (1) (6) can be inferred that the mixture is composed of Na2CO3 and NaHCO3.

The mixture is heated, the component NaHCO3 will be decomposed by heat, 2NaHCO3 = heating = Na2CO3 + H2O + CO2, the reduced mass = M (H2O) + M (CO2), let the number of moles (the amount of substance) containing NaHCO3 in the mixture be X mol, then there are 18 x 1 2x + 44 x 1 2x == , simplified to obtain 31x ==, solution n (NaHCO3) = x = , So the mass of NaHCO3 in the 5g mixture is m(NaHCO3)=nm= x 84g mol=, and the mass of Na2CO3 is m(Na2CO3)= m--m(NaHCO3)==B: white precipitate in solution, Na2CO3 + CO2 + H2O == 2NaHCO3

A mixture of sodium carbonate and sodium bicarbonate.

According to the mass reduction, the mass of sodium bicarbonate is found by the difference method.

The solubility of sodium bicarbonate is small, and white crystals are precipitated.

(1) NaOH generates NaCl when it generates Cu(OH)2 precipitate, and no impurities are introduced.

2）cucl2+2naoh ==cu(oh)2↓ +2naclx

x/135=

x = A: The mass fraction of copper chloride contained in this 30GNacl sample is (3) 100 + 30 + the law of conservation of mass).

Answer: When exactly the complete reaction occurs, the mass of the resulting solution is.

Option 2 should be chosen.

Experimental procedure The 2 reagents were sampled separately and dilute sulfuric acid was dropped.

The experimental phenomenon is to observe which bottle has bubbles formed.

Conclusion: Calcium hydroxide is formed by bubbles.

The chemical equation that produces the white precipitate is CaCO3+H2SO4==CaSO4+H2O+CO2

Exchange and discussion

1 Answer B 2 Answer When pouring the reagent, the label should be turned towards the palm of your hand to prevent the label from being damaged.

Khan: Ask your chemistry teacher to go to such a simple question type.

(1) The chemical formula of gas C is CO2

2) Solid A if it does not contain the element hydrogen, its name is potassium carbonate and the chemical equation of its reaction with clarified lime water is.

ca(oh)2+k2co3==caco3↓+2koh ；If the solid A contains hydrogen, then the name of the substance A is potassium bicarbonate, and the chemical equation of the reaction between the substance and dilute H2SO4 is 2KHCO3+H2SO4==K2SO4+2H2O+2CO2, 3) A certain farmhouse fertilizer containing solid A (without hydrogen elements) is often used in agricultural production, and the main role of applying the substance is (fill in the serial number) C

a Promote the growth of crop stems and leaves, and the leaf color is dark green.

b Promote the development of crop roots and enhance the ability to resist cold and drought.

c. Promote the growth and robustness of crops and enhance the resistance to pests, diseases and lodging.

**Can you be clearer?

Parse] Select C. The composition of a substance cannot be judged by simple observation and must be verified experimentally; There are a lot of toxic substances that are also white solids that are put together with sucrose and may cause some unnecessary injuries or create safety hazards, so c error.

cucl22naoh

cu(oh)2↓2nacl

xx/.9/.1（

The law of conservation of mass.

A, the mass of the solution obtained by the dust is 181: the 30 GnaCl sample contains.

Chlorine Zen copper.

The quality score is:

3）100+30+56-4;30=22: when exactly a complete reaction; 98x=;135=

Answer. 756, no impurities are introduced, and the old staring (1) naoh

NaCl is generated when Cu(OH)2 pellets are generated

1）naoh

NaCl is generated when Cu(OH)2 precipitates are generated, and no impurities are introduced. Trace.

2）cucl2+2naoh

cu(oh)2↓2nacl

xx/135=

x = A: The mass grinding fraction of copper chloride contained in the 30gnacl sample is 3) 100 + 30 + the law of conservation of mass).

Answer: When the world travels and happens to react completely, the mass of the solution obtained is.

1）naoh

When Cu(OH)2 precipitation is generated, NaCl is generated, and no heteroblind plexus deficiency is introduced.

Grinding 2) CuCl2+2NaOH

cu(oh)2↓2nacl

xx/135=

x = A: The mass fraction of copper chloride contained in this 30GNacl sample is (3) 100 + 30 + the law of conservation of mass).

Answer: When it happens to be completely reacted, the Zheng Chun quality of the resulting solution is to hope that it will help you, o( o thank you!)

(bai1) According to the judgment, the chemical formula of FG is: F is Al2O3 and DUG is FeCl2, so the answer is.

zhi：al2o3；daofecl2；

2) Two kinds of gold in the mixture.

The simplest method of genus separation is to use iron to be attracted by magnets, the method is: use a magnet close to the powdered mixture, and adsorb the iron powder on the surface of the magnet, so the answer is: use a magnet close to the powdered mixture, and adsorb the iron powder on the surface of the magnet;

3) In the conversion of d e, X reacts with aluminum chloride to form aluminum hydroxide, according to the laboratory method of preparing aluminum hydroxide and the analysis of the properties of aluminum hydroxide, aluminum hydroxide can be dissolved in excess of strong alkali solution, so adding excess X may be ammonia, so the answer is: C;

4) A C is the reaction of Al and sodium hydroxide to produce sodium metaaluminate and hydrogen, and the chemical equation of the reaction is 2Al + 2NaOH + 2H2O = 2Naalo2 + 3H2; Hi is the oxidation of ferrous hydroxide to iron hydroxide, and the chemical equation of this reaction is: 4Fe(OH)2+O2+2H2O=4Fe(OH)3, so the answer is: 2Al+2NaOH+2H2O=2Naalo2+3H2; 4fe（oh）2+o2+2h2o=4fe（oh）3．

In order to study the properties of a white solid in a chemistry laboratory, a student conducted the following experiment, in which the experimental scheme that you think is incorrect is (c).

Reason: "Three nos": do not touch the medicine with your hands, do not put your nostrils to the mouth of the container to smell the smell of the medicine, and do not taste the smell of any medicine.

According to "solid-white precipitate + excess dilute hydrochloric acid--- precipitate partially dissolved -- colorless solution", it can be known that there must be Baso4 and BaCO3 precipitates, so it must contain BaCl2 and Na2CO3, Na2So4, and CuSo4 and FeCl3 without CuSO4 and FeCl3, because it contains ions that develop color in the solution.

According to "+ excess dilute hydrochloric acid--- precipitate partially dissolved - colorless solution + appropriate amount of silver nitrate solution ---white precipitate 1 + excess nitric acid - precipitate does not disappear", it can be seen that the precipitate with silver nitrate must be silver chloride, but because hydrochloric acid has been added, and the sample contains BaCl2, the origin of chloride ions cannot be verified, so it is impossible to determine whether it contains NaCl, and there is no way to identify the existence of Kno3.

What must not be present in the original white solid is the addition of CuSO4 and FeCl3 to dilute hydrochloric acid: BaCO3 + 2H+ = Ba2+ + H2O + CO2

Colorless liquid 2 must contain Ba2+, H+, NO3-, and the white solid must contain: BaCl2, Na2CO3, Na2SO4, I hope it can help you.

1 Because hydrochloric acid is added to obtain a colorless solution, there must be no CuSO4 FeCl3 in the original white solid.

2 BaCO3+2HCl=BAC2+H2O+CO2 3 There must be sodium nitrate nano3 and barium nitrate BA(NO3)2 in the colorless liquid 2.

4 The original white solids must be present: BaCl2 Na2CO3 Na2SO4