Does hexavalent chromium have to be reduced to trivalent chromium under acidic conditions?

1) In 2K2Cr2O7+3CH3CH2OH+8H2SO4=2K2SO4+2CR2(SO4)3+3CH3COOH+11H2O, ethanol, acetic acid, and water retain the chemical formula in the ion reaction, then the corresponding ion reaction is 2Cr2O72-+3CH3CH2OH+16H+=4Cr3++3CH3CoOH+11H2O, so the answer is: 2Cr2O72-+3CH3CH2OH+16H+=4cr3++3ch3cooh+11h2o；

2) The driver is drunk driving, and 2K2Cr2O7 + 3CH3CH2OH + 8H2SO4 = 2K2SO4 + 2CR2 (SO4) 3+3CH3CoOH + 11H2O, when the positive trivalent chromium is reduced and generated, the color changes to green, and it is observed that the silica gel in the device will change from orange-red to green, so the answer is: orange-red; Green;

3) When the valency of CR element decreases, K2Cr2O7 is the oxidant, and the obtained electrons are reduced, and Cr2(SO4)3 is the reduction product. If the valency of element C increases, CH3CH2OH is the reducing agent, and if it loses electrons and is oxidized, then CH3COOH is the oxidation product, so the answer is: K2Cr2O7; ch3ch2oh；ch3cooh；cr2（so4）3；

4) The amount of ethanol is a substance.

69g46g/mol

The binding reaction shows that in the presence of 2K2Cr2O7 3CH3CH2OH, the amount of substances that consume K2Cr2O7 is.

1mol, so the answer is: 1mol

Hydrogen peroxide cannot oxidize trivalent chromium to hexavalent chromium under acidic conditions, but it can do so under wear-resistant alkaline conditions.

2cr(oh)3 + 3h2o2 + 4oh- =2cro42- +8h2o

There have been experiments to analyze the chromium content, and the test process should convert trivalent chromium into hexavalent, in which in the case of adding strong trembling acid, such as concentrated sulfuric acid and concentrated sulfuric acid mixed acid, concentrated nitric acid can also be oxidized to hexavalent. Especially in the case of heating, the current trivalent chromium passivation solution generally does not contain hexavalent chromium (but the market is also made of hexavalent chromium reduction) If hexavalent chromium is found, there are three possibilities One is that a strong oxidant such as potassium permanganate is added to the passivation solution, which is more oxidizing than hexavalent chromium, so it can oxidize trivalent chromium to hexavalent chromium The other possibility is that a little hexavalent chromium is added to the passivation liquid, so that the passivation film can not detect hexa** (EPA3060A 7916). IEC62321 colorimetric method), but there is also an error in the detection method, because the concentration of ppm level is difficult to say whether it is accurate In addition, it has a lot to do with washing, drying and preservation in the passivation process It is also possible that the trivalent chromium potion is stained by hexavalent chromium dust liquid Trivalent chromium passivation water washing is not good, it is easy to exceed the standard, and the higher the concentration of trivalent chromium, the easier it is to exceed the standard At the same time, the humidity environment will make the trivalent chromium in the film to hexavalent chromium convert The oxidant and catalyst in the trivalent chromium potion may oxidize the trivalent chromium to hexavalent chromium, but it is difficult to do the other in an acidic environment: the oxidant and catalyst in the trivalent chromium potion may oxidize the trivalent chromium to hexavalent chromium (the electroplating treatment is more likely to be color zinc plating black zinc) chromium plating and its pharmaceutical solvent itself is hexavalent chromium, which is electrolyzed into a elemental chromium gold pie hole species, such as the handle of the door (of course, the process should pay attention to the cross-contamination of the process).

Under the conditions of high temperature and the presence of oxidant, it will oxidize to hexavalent chromium. Chromium element symbol CR, silvery-white metal, belongs to group B in the periodic table, the atomic number of chromium is 24, atomic weight, stuffy body-centered cubic crystal, the common valency is +3, +6 and +2, and the oxidation number is 10.

Ferrous chromite and mafic chromite are often referred to as chromite. Chromite is an equiaxed crystal system, the crystal is a fine octahedral, usually granular and dense massive aggregates, the color is black, the streaks are brown, semi-metallic luster, hardness, specific gravity, and weak magnetism.

Chromite is a magmatic mineral, produced in ultramafic rocks, when the ore-bearing rocks are weathered and damaged, chromite is often transferred to placers. Chromite is the most important mineral raw material for chromium smelting, and the inferior ore rich in iron can be used as a high-grade refractory material.

Expand the information of the filial piety:

Chromium has a silvery-white lustrous metal, pure chromium is malleable, and chromium with impurities is hard and brittle. Density. Soluble in strong alkaline solution.

Chromium is highly resistant to corrosion and oxidizes slowly in air, even in a red-hot state. Insoluble in water. Plating on metal can play a protective role.

The preparation of chromium trioxide can be done by ammonium chloride reduction method. That is, a certain amount of ammonium chloride is mixed into the sodium dichromate crystal, mixed and reduced at 700 800 in the reduction furnace, and then the NaCl is washed off, and the chromium trioxide filter cake is filtered to obtain it, which is dried and crushed, and calcined at 1150 1200 in the rotary kiln. The chromium trioxide obtained by this method is dark green, with large particles and high purity, but there are many production processes and produces harmful gas HCl.

The calcined chromic anhydride method adds sodium dichromate to the reaction pot, injects concentrated sulfuric acid, and reacts sodium dichromate with sulfuric acid at 200 degrees to produce chromic anhydride.

Summary. Glycolic acid can reduce hexavalent chromium to trivalent chromium. This is because glycolic acid is a reducing agent that can donate electrons to hexavalent chromium to reduce it to trivalent chromium. In this process, the glycolic acid itself is oxidized to acetic acid.

Glycolic acid can reduce hexavalent chromium to trivalent chromium. This is because glycolic acid is a reducing agent that can provide electrons to hexavalent chromium, so that it can be reduced to trivalent Zheng socks chromium. In this process, the glycolic acid itself is oxidized to acetic acid.

The hydroxyl group (OH) in glycolic acid and the carbonyl group (C=O) in the carboxyl group (COOH) both open and crack groups that can provide electricity and silently shut down, so glycolic acid can be used as a reducing agent to reduce hexavalent chromium to trivalent chromium. In this process, hexavalent chromium accepts electrons and is reduced to trivalent chromium, while the hydroxyl and carboxyl groups in glycolic acid are oxidized to water and carbon dioxide.

OK. A unit vector is a vector of length 1 that can be used to represent direction. Any non-zero vector can be expressed as the product of a standard-leak circle and a unit vector, i.e.,

v** v**|u** where |**v**|is the length of the vector v, and u, which is the same direction as the coarse v. Thus, we can use a unit of rock raid to represent the direction of any non-zero vector.

Summary. Hexavalent chromium is an environmentally harmful compound that exhibits oxidation under certain conditions. Hexavalent chromium usually exhibits high oxidation under acidic conditions, because under acidic conditions, hexavalent chromium will be converted into more oxidizing acidic chromate ions (CRO4-), and under acidic conditions, it is easy to form a relatively stable Cr2O7-2 ion, so the oxidation reaction of hexavalent chromium can be accelerated in an acidic environment.

In addition, hexavalent chromium is also prone to oxidation under high temperature conditions and in the presence of certain strong oxidizing agents. In short, hexavalent chromium is prone to oxidation when it is in an acidic environment, at high temperatures, and in the presence of strong oxidants. It has an impact on the environment and human health, so it should be taken seriously.

Hexavalent chromium is an environmentally harmful compound that exhibits oxidation under certain conditions. Hexavalent chromium usually shows high oxidation under acidic conditions, because under acidic conditions, hexavalent chromium will be converted into more oxidizing acid chromate ions (CRO4-), and under acidic conditions, it is easy to form a relatively stable Cr2O7-2 ion, so the oxidation reaction of hexavalent chromium can be accelerated under the influence of an acidic environment. In addition, hexavalent chromium is also prone to oxidation under high temperature conditions and in the presence of certain strong oxidants.

In short, hexavalent chromium is prone to oxidation when it is in an acidic environment, at high temperatures, and in the presence of strong oxidants. It will have an impact on the environment and human health, so it should be paid enough attention.

Can you elaborate on that a little bit more?

Hexavalent chromium is an environmentally harmful compound that exhibits oxidation under certain conditions. Hexavalent chromium usually shows high oxidation under acidic conditions, because under acidic conditions, hexavalent chromium will be converted into more oxidizing acid chromate ions (CRO4-), and under acidic conditions, it is easy to form a relatively stable Cr2O7-2 ion, so the oxidation reaction of hexavalent chromium can be accelerated under the influence of an acidic environment. In addition, hexavalent chromium is also prone to oxidation under high temperature conditions and in the presence of certain strong oxidants.

In short, hexavalent chromium is prone to oxidation when it is in an acidic environment, at high temperatures, and in the presence of strong oxidants. It will have an impact on the environment and human health, so it should be paid enough attention.

No. It is only possible under alkaline conditions.

2cr(oh)3 + 3h2o2 + 4oh- =2cro42- +8h2o

Hydrogen peroxide (chemical formula: H2O2), pure hydrogen peroxide is a light blue viscous liquid, miscible with water in any proportion, is a strong oxidant, aqueous solution is commonly known as hydrogen peroxide, is a colorless transparent liquid.

Chemical properties. 1.Oxidation.

In oil paintings, the lead white [basic lead carbonate] reacts with hydrogen sulfide in the air to form black lead sulfide, which can be washed with hydrogen peroxide).

Principle: lead sulfide, lead oxide, basic lead carbonate (alkaline medium is required).

2.Reducibility Reacts with strong oxidants such as chlorine and potassium permanganate to produce oxygen.

3.In 10ml of 10% sample solution, add 5ml of dilute sulfuric acid solution (TS-241) and 1ml of potassium permanganate solution (TS-193). Bubbles should occur, and the purplish-red color of potassium permanganate disappears. It is acidic to litmus. It is explosive in case of organic matter.

4.Take 1g of sample (accurate to, dilute with water to. take 25ml of this solution, add 10ml of dilute sulfuric acid test solution (TS-241) and titrate with potassium permanganate. per milliliter. Potassium permanganate is equivalent to hydrogen peroxide (H2O2).

5.In case of organic matter, oxygen and water are liberated by heating, and the reaction is violent in case of chromic acid, potassium permanganate, metal and carbonic acid. In order to prevent decomposition, trace amounts of stabilizers such as sodium stannate, sodium pyrophosphate, and so on can be added.

6.Hydrogen peroxide is an extremely weak acid: H2O2 = (reversible) = H++Ho2- (Ka=. Therefore, the peroxide of the metal can be regarded as its salt.

7.Pure hydrogen peroxide is very unstable and violently decomposes into water and oxygen when heated to 153 °C.

Hydrogen peroxide does not oxidize trivalent chromium ions to hexavalent chromium under acidic conditions, but it can do so under alkaline conditions.

2cr(oh)3 + 3h2o2 + 4oh- == 2cro42- +8h2o

There has been a test to analyze the chromium content, and the test process should convert trivalent chromium into hexavalent, in which in the case of adding strong acid, such as concentrated sulfuric acid and concentrated sulfuric acid mixed acid, concentrated nitric acid can also be oxidized to hexavalent. Especially in the case of heating, the current trivalent chromium passivation solution generally does not contain hexavalent chromium (but the market is also reduced from hexavalent chromium) If hexavalent chromium is found, there are three possibilities One is that a strong oxidizing agent such as potassium permanganate is added to the passivation solution, which is stronger than hexavalent chromium, so it can oxidize trivalent chromium to hexavalent chromium The other possibility is that a little hexavalent chromium is added to the passivation liquid, so that the passivation film obtained can not detect hexa** (colorimetric method), but there is in the solution There is also the error of the detection method, because it is difficult to say whether the concentration of ppm level is accurate In addition, it has a lot to do with the washing, drying and preservation of the passivation process It is also possible that the trivalent chromium solution is contaminated by hexavalent chromium Trivalent chromium passivation water washing is not good, and the higher the concentration of trivalent chromium, the easier it is to exceed the standard At the same time, the humidity environment will convert the trivalent chromium in the film to hexavalent chromium The oxidants and catalysts in the trivalent chromium solution may oxidize the trivalent chromium to hexavalent chromium. However, it is difficult to change in an acidic environment: the oxidant and catalyst in the trivalent chromium potion may oxidize the trivalent chromium to hexavalent chromium (the more likely electroplating treatment is color zinc plating and black zinc), and the chromium plating solvent itself is hexavalent chromium, which is electrolyzed into elemental chromium metal, such as the handle of the door (of course, the process should pay attention to the cross-contamination of the process).