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The concentration of hydrochloric acid is about 37% and is a non-oxidizing acid. The main component of stomach acid is also hydrochloric acid.

Iron and non-oxidizing acids react to produce Fe2+ (ferrous ions, light green), and oxidizing acids to obtain Fe3+ (iron ions, yellow), and iron is passivated in concentrated sulfuric acid and concentrated nitric acid. Iron and Fe3+ are reacted to give Fe2+

2fecl3+fe=3fecl2

If hydrochloric acid reacts with iron, the resulting FeCl2 passivates the surface and the reaction cannot proceed. If iron reacts well with hydrochloric acid, then a person can really digest iron.

It is generally believed that iron and hydrochloric acid do not react. But at high temperatures, iron can react with water vapor to form ferric tetroxide and hydrogen.

3fe+4h2o=fe3o4+4h2

Therefore, when extremely dilute hydrochloric acid reacts with iron at high temperatures, it is actually water and iron that react.

It should be noted that since most acids can ionize H+ when dissolved in water, hydrogen ions have weak oxidation, so acids have weak oxidation.

What we usually call non-oxidizing acids refers to acids that can only exhibit weak oxidizing properties of hydrogen ions in the reaction. Such as: HCl, HBR, H2CO3, dilute H2SO4

Fe + 2 HCL = = = FeCl2 + H2 (overflow).

Dilute hydrochloric acid and concentrated hydrochloric acid are only the difference in concentration, and the properties are the same, because the concentration of concentrated hydrochloric acid is only more than 30%, and there will be no qualitative change.

Upstairs is very right, it's all the same, except that concentrated hydrochloric acid is volatile, and it will be mixed with HCL gas in the product, but the equation is the same.

fe+2hcl==fecl2+h2

Dilute hydrochloric acid is the same as concentrated hydrochloric acid.

The pH value of 1 is 2, which means that it is acidic, only acid can react with iron, and alkali is not reactant, you should know.

That's why I chose A. Hope.

Because concentrated hydrochloric acid turns Fe into Fe3+

1) A Use a separating funnel as gas may spill through a long-necked funnel.

2) Adjust the height of the graduated cylinder so that the liquid level is flush with the jar. Because it is necessary to ensure that the air pressure on both sides is equal, otherwise the gas is not the standard condition.

3) No The molar volume of the gas is the same under the standard condition, and air or CO2 did not have a great effect in the past.

4) Excessive HCI reacts with the generated NAHCO3 to form NACI, CO2, and the gas is increased.

5) Because the sample size is too large, the liquid will overflow or the gas will escape, resulting in inaccurate measurement; Too little will cause too little gas and not enough air pressure to be generated, resulting in a large error.

1) A (2) Remove the catheter and place the graduated cylinder flat with the line of sight tangent to the lowest part of the concave surface of the solution.

3) None (4) Too large (5) Because too much sample size will cause liquid overflow or gas escape, resulting in inaccurate measurement; Too little will cause too little gas and not enough air pressure to be generated, resulting in a large error.

White vinegar and liquor.

Differentiating methods: smell the taste; Phenomena: sour and winey, respectively; Conclusion: The sour taste is white vinegar, and the aroma of wine is white wine.

Ice cubes and glass.

Method of differentiation: slightly heated; Phenomenon: Can and will not melt; Conclusion: It is ice that can melt, and glass that does not.

Gas and air.

Differentiating methods: smelling odors; Phenomenon: with and without special odor; Conclusion: Natural gas has a special odor, and air has no special smell.

1. Condense and reflux the evaporated toluene and water; A 2. Keep the liquid from boiling; Stop heating, add zeolite 3 and potassium permanganate in small quantities after cooling; The liquid in the three-mouth bottle is not stratified 4, to prevent benzoic acid from precipitating from the solution after cooling; Drain with a glass rod and add distilled water to the funnel until the filter residue is submerged 5, C (the color is due to the excess KMno4 residue, add sodium bisulfite to reduce) 6, evaporation and concentration, cooling and crystallization.

The outermost electron, 8, stable, 4, lost, 4, gained, 2:11:2

Fixed, fixed, 1

11.(1)h2o、no、nh3，o2 (2)④ 3)4nh3+5o2=4no+6h2o 12.(1) volatile organic compounds (2) H2O (3) CO2,

Please do it yourself carefully, and ask again if you don't know it.

11.(1) H2O, sedan town NO, closed town coarse NH3, O2 (2) 3) 4NH3+5O2=4NO+6H2O 12(1) volatile organic compounds (2) H2O (3) CO2,

a. Error. Because Cus and Zns are AB-type compounds, the larger the KSP, the greater the solubility. Therefore, the solubility of zns is large b, and the ruler is empty.

H2S is a weak acid, and the concentration of S2- in the H2S solution of mol L, the concentration of S2- is definitely less than that of mol L, so the maximum concentration of Cu2+ is not KSP C.