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Povna characteristic of chromium. Physical power and mechanical characteristics of chromium metal and spoluk. Melting temperature and temperature

Зміст statty

CHROMIUM- (Chromium) Cr, chemical element 6 (VIb) of the Periodic system. Atomic number 24, atomic carriage 51.996. From 24 to isotope chromium from 42 Cr to 66 Cr. Isotopes 52 Cr, 53 Cr, 54 Cr are stable. Isotope storage of natural chromium: 50 Cr (period in the westward 1.8 10 17 rocks) - 4.345%, 52 Cr - 83.489%, 53 Cr - 9.501%, 54 Cr - 2.365%. The main stages of oxidation are +3 and +6.

In 1761, Professor of Chemistry of St. Petersburg University Johann Gottlob Lehmann (Johann Gottlob Lehmann), a wondrous grain of the Ural mountains at the Berezovskiy mine, evolved a miraculous red mineral, which was old when it was taken away U 1766 p. Lehman brought a guide to the mineral to St. Petersburg. Having overburdened the crystals with hydrochloric acid, wiping off the sieges, wiping out lead. Lehman called the mineral Siberian worm-name lead (plomb rouge de Sibérie), now vidomo, scho tse buv krokoit (from the walnut "krokos" - saffron) - a natural chromate with lead PbCrO 4.

Nimetsky mandrivnik and pre-eminent of nature Peter Simon Pallas (1741-1811), having funded the expedition of the St. Pallas wrote: “The whole divine red lead mineral does not develop in a fast birth. When rostirannі into powder we stand, and maybe butirustanium artistic miniatures". Unimportant on the occasion and difficult delivery of crocodiles from the Berezovsky mine to Europe (there were two rocks at the end of the day), the victorious mineral yak barvnik was well-estimated. London and Paris have 17 Art. All the noble individuals traveled in carriages, smothered with a crumbly crocoite, besides, they brushed the Siberian red lead with lead added to the collection of baguettes of minerological cabins in Europe.

U 1796 p. Having spent a little time to eat up to the professor of chemistry at the Parisian Mineralogical School, Nicolas-Louis Vauquelin (1763–1829), who analyzed the mineral, but did not know, there is no aluminum of this lead crystal. Prodding the dosage of Siberian chervony with lead, Vokelen prokip'yativ mineral with potash and send a white siege to lead carbonate by cutting off the rosters of undesirable salt. With the obrobtsі th sіll with lead, the sieges are set, the mercury - chervonia, and with the addition of tin chloride, the growth becomes green. Razkladayu crocoite with mineral acids, wine removing the difference "acid and red lead", the vaporization of which yielded ruby-chervony crystals (at the same time zrozumilo, as well as chromium anhydride). Having fried them in a graphite crucible, having reacted to the reaction of helpless young silver crystals of metal, which had never been home to that hour. Vauckelen noted the high refractoriness of the metal and its resistance to acids.

Vauckelin called the new element chromium (from the walnut crwma - color, zabarvlennya) with a glance at the bezel-colored spoluk, which he approved of. At the present time, Vokelen made the first statement that the smaragdovs of the expensive stones are explained by the house in them and the chrome. For example, natural smaragd є is fabulous in green greens of beryl, in which aluminum is partially substituted with chromium.

Shvid for everything, Vauckelin, having cut off not pure metal, but yogo carbidi, just to witness the bare form of the cutoff crystals, Ale Parizka Academy of Sciences protesting the display of a new element, and at the same time Vokelen rightly gets involved in the persistence of elements No. 24.

Yuriy Krutyakov

Chromium is recognized until the period of boiling development of chemical and analytical dosages of salts and minerals. In Russia, chemists had a special interest in the analysis of minerals that were known to Siberia and those who were not to Western Europe... One of such minerals is Bula Siberian chervona, lead ore (crocoite), described by Lomonosov. Mineral doslidzhuvsya, albeit nothing, except for lead oxides, zinc and aluminum, has not yet been known. However, in 1797, Vokelen's rotsi, having subtly refined the minerals with potash and precipitated carbonate with lead, trimmed the roschin, made up in an orange-red color. The most wide range of crystals was crystallized in the ruby-chervon sil, for which they saw oxide and virgin metal, in the form of all types of metals. Vaukelen calling yogo Chromium ( Chrome ) as a walnut word- farbuvannya, color; the truth here was about power, the power is not metal, as well as the well-made salts.

Knowledge from nature.

Naivazhliv_shoyu ore chrome, scho maє practical value, є chromite, approximate warehouse of a different form of the formula FeCrO ​​4

Wine grows up in Maliy Asia, in the Urals, in Wine of America, Pivdens of Africa. The technical meaning can also be called mineral crocoite - PbCrO 4. In nature, also chromium oxide (3) and deyakі іnshі yogo spoluky can be found. Have earth measles instead of chromium at a pererakhunku for metal to become 0.03%. Chromium is revealed on Sonts, stars, meteorites.

Physical power .

Chromium is bilium, hard and tendency metal, but chemically resistant to acids and meadows. On the other hand, it is oxidized, so the surface can be thinned with a thin layer of oxide. Chromium weight is 7.1 g / cm 3 and the melting temperature becomes +1875 0 С.

Otrimannya.

With a strong heating of the chromium zaliznyak from the vugilli, the renewal of chromium and zaliza occurs:

FeO * Cr 2 O 3 + 4C = 2Cr + Fe + 4CO

As a result of the whole reaction, an alloy of chromium and gold is established, which leads to a high performance. To remove pure chromium from chromium oxide (3) aluminum:

Cr 2 O 3 + 2Al = Al 2 O 3 + 2Cr

At the end of the process, two oxides - Cr 2 O 3 and CrO 3

Cheerful authorities.

Thin powder leaves to oxide, which cover the surface with chromium, wine is even stiffer to the level of aggressive acids and meadows. Chromium does not react with concentrated nitric and hydrochloric acids, as well as with phosphoric acid. In the meadows, chromium enters into interaction at t = 600-700 about C. However, chromium interacts with the cultivation of hydrochloric acids and hydrochloric acids, vitisnyayuchi water:

2Cr + 3H 2 SO 4 = Cr 2 (SO 4) 3 + 3H 2
2Cr + 6HCl = 2CrCl 3 + 3H 2

For high temperatures, chromium burns in acid, an oxide (III) can be used.

Chromium reaction with vapors:

2Cr + 3H 2 O = Cr 2 O 3 + 3H 2

Chromium at high temperatures also reacts with halogens, halogen - water, water, nitrogen, phosphorus, vugillam, silicon, boron, for example:

Cr + 2HF = CrF 2 + H 2
2Cr + N2 = 2CrN
2Cr + 3S = Cr 2 S 3
Cr + Si = CrSi

Vishchevkazanі physical and chemical authorities chrome knew their zasosuvannya in other regions science and technology. So, for example, chrome and yogo alloy is used for rejection of high-quality, corrosion-resistant coatings from machines. Alloy at the ferrochrome vyglyadі vykorystovuyut yak metal іnstrumenti. Chrome-minded people knew that they were stuck in medical technology, with the preparation of chemical technological possession.

Positioning chrome in periodic systems chemical elements:

Chrome ocholyu will defeat the group VI group periodic systems elements. Yogo electronic formula is as follows:

24 Cr IS 2 2S 2 2P 6 3S 2 3P 6 3d 5 4S 1

In the stored orbital with electrons, the chromium atom will break the regularity, but from which the small number is stored 4S - the orbital to the 4S 2. However, in addition to the fact that 3d is the orbital loan in the atom of chromium, it is less energetic than it should be, it is displayed with the value 4d 5. It is also a manifestation of being in the middle of the elements of the secondary groups. Chromium can be oxidized from +1 to +6. The most stable є half chrome with oxidation steps +2, +3, +6.

Z'єdannya bivalent chromium.

Chromium (II) oxide CrO - pyrophoric black powder CrO is available in hydrochloric acid dilutions:

CrO + 2HCl = CrCl 2 + H 2 O

On turn, at heating at 100 0 С, CrO transforms into Cr 2 O 3.

The salts of bivalent chromium are established for an hour when chromium metal is resolved in acids. Cycle reactions are generated in an atmosphere of low-activity gas (for example, H 2), because in the presence of a powder, oxidation of Cr (II) to Cr (III) is easy to see.

Chromium hydroxide to win a siege in a viglyadі zhovtoy when breaking a meadow for chromium (II) chloride:

CrCl 2 + 2NaOH = Cr (OH) 2 + 2NaCl

Cr (OH) 2 is the main power, є the protagonist. Hydratization of Cr2 + ions in black-and-white colors. Water solution CrCl 2 oil blue On turns, at water levels, the Cr (II) spoloks pass at the Cr (III) spoludes. Especially it is possible to appear in Cr (II) hydroxide:

4Cr (OH) 2 + 2H 2 O + O 2 = 4Cr (OH) 3

Z'єdnannya trivalent chromium.

Chromium (III) oxide Cr2O3 is a refractory powder of green color. For hardness close to corundum. In the laboratory, it is possible to classify the following dichromate as ammonia:

(NH 4) 2 Cr 2 O 7 = Cr 2 O 3 + N 2 + 4H 2

Cr 2 O 3 - amphoteric oxide, when fused in meadows, solidified chromium: Cr 2 O 3 + 2NaOH = 2NaCrO 2 + H 2 O

Chromium hydroxide is also an amphoteric spoluco:

Cr (OH) 3 + HCl = CrCl 3 + 3H 2 O
Cr (OH) 3 + NaOH = NaCrO 2 + 2H 2 O

Anhydrous CrCl 3 may look like leaves in a dark violet colorah, it is unrepentant in cold water, with boiling wine it grows more often. Anhydrous sulfate chromium (III) Cr 2 (SO 4) 3 horny colora is also rotten at water. In the presence of the witnesses, violet sulfate is approved for chromium Cr 2 (SO 4) 3 * 18H 2 O. Also green hydrates for chromium sulfate, in order to take away less water. Chromium galloon KCr (SO 4) 2 * 12H 2 O crystallizes from the breaks, so that violet sulfate is replaced with chromium and calcium sulfate. The growth of chromium galuns when the greens are heated with the preparation of sulfates.

Reactions with chromium and yogo

Mayzhe all the half-chrome ones, and the smallest ones, are intensively worked up. Mayuchi bezbarvny razchin or more sieges, we may be with the great imovirn_styu of the growth of visnovok about the visibility of chromium.

  1. Strongly heated in the half of the pallet on the porcelain bowl, such as a bit of bichromate calyu, to fit on the tip of the knife. I can't see crystallized water, but melt at temperatures close to 400 0. Pogrієmo її shche kіlka kіlina on the strong half. Pislya cooled to a crock to pretend to be green sieges. A part of it is located near the water (there is a nabuva zhovtoy koloru), and a part of it is superfluous on the tile. When heated, the silt opened up, and the result was a pinky chromate of K 2 CrO 4 and greens Cr 2 O 3.
  2. Rozchinniy 3g of powder-like bichromate calium in 50ml of water. Up to one part of the dodamo trocha is carbonated with calium. We will be able to find out about the CO2 vision, and the balance will become light - we will be happy. Chromate is applied to the bichromate of kaliyu. If now add up to 50% of the proportions of sirchanoic acid, then I know it will be red - chew bichromate.
  3. Nallumo at a test tube 5 ml. We will use the calcium bichromate, prokip'yat from 3 ml of concentrated hydrochloric acid and under the traction. From the point of view of the green-green color, the branched gaseous chlorine, fragments of chromate are oxidized with HCl to Cl 2 і H 2 O. The chromate itself is transformed into green chloride trivalent chromium. Yogo can be seen in viparyuvannya razchin, and then, having fused with soda and celite, translated into chromate.
  4. When added to the amount of lead nitrate, lead chromate is used; in case of interaction with the solution to the nitrate of the medium, a red-brown siege to the chromate of the medium is established.
  5. Dodamo peroxide is water-based up to a bichromate and acidic acid. Rozchin nabuvaє glyboky blue kolor zavdyaki approved with chromium peroxide. When peroxide is removed with a small amount of ether, go to the organic store and store it in the black color. The reaction is specific to chromium and is even more sensitive. With this help you can find chromium in metals and alloys. Before it is necessary to break the metal. With trivial boiling with 30% hydrochloric acid (it is possible to add hydrochloric acid), chromium and a lot of chrome began to deteriorate frequently. Otrimany rozchin revenge sulfate on chromium (ІІІ). It is possible to carry out a reaction of detection, with a combination of neutralizing and liquid sodium. In the siege of siro-greens, chromium (III) hydroxide, which is too much NaOH, will fix the greens with sodium chromite. Professional solutions and dodamo 30% water peroxide. When the rosters are heated, they can become too cold, and the fragments of chromite oxidize to chromate. Pidkislennya prizvede until the blakitny zaparvlennya razchinu appears. Zabarvlene z'єdnannya can be extraguvated, crushing with ethereum.

Analytical reaction to chromium.

  1. Up to 3-4 specks for chromium chloride CrCl 3, apply 2M NaOH solutions until the siege is resolved, with a sprinkle of water. Beastly respect for the sodium chromite color, as soon as you make up your mind. Heat the disagreements on the water bath. What about when you see?
  2. Up to 2-3 drops of size CrCl 3 give a small volume of 8M size of NaOH і 3-4 drops of 3% size of H 2 O 2. Heat the reaction sum in a water bath. What about when you see? How can a siege be set up, how can we remove neutrality from problems, add up to CH 3 COOH, and then Pb (NO 3) 2?
  3. Pour 4-5 drops into a test tube with chromium sulfate Cr 2 (SO 4) 3, IMH 2 SO 4 and KMnO 4. Heat the reaction of the sum with a stretch of some quilting in the water bath. Beastly respect for the change of the farbuvannya razchin. Chim wono spricinene?
  4. Up to 3-4 drops of acidified with nitric acid K 2 Cr 2 O 7 give 2-3 drops of H 2 O 2 and mix. Syn farbuvannya the difference, which appears, was poured over the claims of perchromic acid H 2 CrO 6:

Cr 2 O 7 2- + 4H 2 O 2 + 2H + = 2H 2 CrO 6 + 3H 2 O

Beast to respect on the H 2 CrO 6:

2H 2 CrO 6 + 8H + = 2Cr 3+ + 3O 2 + 6H 2 O
blue color green color

Nadchromic acid is significant in organics.

  1. Up to 3-4 drops of acidified with nitric acid K 2 Cr 2 O 7 give 5 drops of isoamyl alcohol, 2-3 drops of H 2 O 2 size and add the reaction sum. A ball of an organic razchinnik, which spills to the top, finished in a bright-blue color. Zabarvlennya znikaє povіlno. Measure the strength of H 2 CrO 6 in organic and aqueous phases.
  2. In the case of the interaction of CrO 4 2 and ions Ba 2+, the precipitation of precipitates to the chromate barium BaCrO 4.
  3. Nitrate of the medium set up with ions of CrO 4 2 sieges to chromate of the medium of celadon-chervony kolor.
  4. Take three tubes. Put 5-6 drops of K 2 Cr 2 O 7 in one of them, in the other - the same amount of K 2 CrO 4, and in the third - three drops of both sizes. Then add three drops of calcium iodide to the skin tube. Explain the result. To acidify the differences from other samples. What about when you see? For what?

Tsіkavі until іf chrome spikes

  1. Sumish CuSO 4 і K 2 Cr 2 O 7 at the addition of the meadow becomes green, and at the presence of acid it is old. Heated 2 mg of glucerin with a small amount of (NH 4) 2 Cr 2 O 7 with additional addition of alcohol, for filtering to use sweet greens, such as when acid was added and aged, and in the middle, low green puddles.
  2. Place in the center of the canning jar with the term "rubinov sumish" - a lid and room for aluminum foil Al 2 O 3 (4.75 g) with the addition of Cr 2 O 3 (0.25 g). I haven’t reached the can before, it is necessary to bury the top image at the pips, and when the term is ready for that cob of reaction, cover it with a golden leaf and pick it up. Bank vicopati for doba. Through the wine, a red ruby ​​powder is established.
  3. Rub 10g of bichromate calories with 5g sodium nitrate or calories and 10g zukru. Summing up and down from the decks. As soon as the powder is pressed from the glass pipes, and then when you wipe the stick and fire it from the butt, then it’s more like “snake”, a little bit of chorn, and when it is cold it is green. A stick with a diameter of 4 mm burns close to 2 mm for a second and will burn tenfold.
  4. If you change the difference between the sulfate and the dichromate of the calcium and add the amount of amorphous brown sediment to the store 4CuCrO 4 * 3NH 3 * 5H 2 O, which can be found in hydrochloric acid in order to make the greens, and the necessary As far as possible, add alcohol to the range of greens of siege, as if the filter is blue, and when it hangs - blue-violet with red sparkles, kindly visible with strong illumination.
  5. chromium oxide, which has become overflowing with the slides of the "volcano" or "pharaohs' serpents", can be regenerated. For the whole requirement of alloying 8 g Cr 2 O 3 і 2 g Na 2 CO 3 і 2.5 g KNO 3 and sprinkle the cooling with sprinkles. It is possible to use a pink chromate, which can be reconverted on the other side of Cr (II) and Cr (VI), in which case it is an external dichromate of ammonia.

Apply oxide-intermediate transitions for the participation of chromium and yo spoluk

1. Cr 2 O 7 2- - Cr 2 O 3 - CrO 2 - - CrO 4 2- - Cr 2 O 7 2-

a) (NH 4) 2 Cr 2 O 7 = Cr 2 O 3 + N 2 + 4H 2 O b) Cr 2 O 3 + 2NaOH = 2NaCrO 2 + H 2 O
c) 2NaCrO 2 + 3Br 2 + 8NaOH = 6NaBr + 2Na 2 CrO 4 + 4H 2 O
d) 2Na 2 CrO 4 + 2HCl = Na 2 Cr 2 O 7 + 2NaCl + H 2 O

2. Cr (OH) 2 - Cr (OH) 3 - CrCl 3 - Cr 2 O 7 2- - CrO 4 2-

a) 2Cr (OH) 2 + 1 / 2O 2 + H 2 O = 2Cr (OH) 3
b) Cr (OH) 3 + 3HCl = CrCl 3 + 3H 2 O
c) 2CrCl 3 + 2KMnO 4 + 3H 2 O = K 2 Cr 2 O 7 + 2Mn (OH) 2 + 6HCl
d) K 2 Cr 2 O 7 + 2KOH = 2K 2 CrO 4 + H 2 O

3. CrO - Cr (OH) 2 - Cr (OH) 3 - Cr (NO 3) 3 - Cr 2 O 3 - CrO - 2
Cr 2+

a) CrO + 2HCl = CrCl 2 + H 2 O
b) CrO + H 2 O = Cr (OH) 2
c) Cr (OH) 2 + 1 / 2O 2 + H 2 O = 2Cr (OH) 3
d) Cr (OH) 3 + 3HNO 3 = Cr (NO 3) 3 + 3H 2 O
e) 4Cr (NO 3) 3 = 2Cr 2 O 3 + 12NO 2 + O 2
f) Cr 2 O 3 + 2 NaOH = 2NaCrO 2 + H 2 O

Element chrome at the role of the artist

Khimiks often turned to the problem of the establishment of piecemeal pigments for painting. At the XVIII-XIX centuries, the technology of rejection of bagatyokh materials was broken. Lui Nikola Vauquelin in 1797, having appeared at the Siberian chervoniy ore earlier than nevidomy element chromium, having prepared a new, wonderful style of farb - chrome greens. Chromophore - hydrous oxide of chromium (III). With the name "Smaragdova Green", they celebrated the fate of 1837. Piznishe L. Vokelen proponated a sprinkle of new farbs: barite, zinc and chromium zhovt. In the meantime, the stench of a boule of vitisneni with stiff, orange-colored pigments based on cadmium.

Zelena Khromova - mitsna and svitlostiyka farb, so as not to be fed into the flow of atmospheric gases. Rosterta on olії chrome greens has great strength, and it’s great to hang out, since the 19th century. її is widely used in painting. More majesty is won by the list of porcelains. On the right, in that porcelain virobi can be decorated with either an overglaze or overglaze pattern. In the first place, apply a farbi vipad on the surface of a leftover viroba, which is then covered with a ball of glaze. Further along the main, high-temperature vipal: for the sintering of porcelain mass and melting of glaze, virobi heat up to 1350 - 1450 0 С. Black oxide of cobalt, applied to the surface of a porcelain viroba, during vipalyuvanny it is fused with glaze, chemically together with it. As a result, yaskravo-blue silikati cobalt is set. Such decalcation of blue porcelain dishes with cobalt should be well known. Chromium (III) oxide is not modular with the components of the glaze;

Krim chrome green artists zasosovyat farbi, otrimanі z volkonsky. Cei mineral iz group of montmorilonites (clay mineral to the class of folding silikats Na (Mo, Al), Si 4 O 10 (OH) 2 vyavili 1830 r. Raevsky, the squad of the Decembrist S.G. Volkonsky.Volkonsky is a clay that can cover up to 24% chromium oxide, as well as aluminum oxide and zinc (III). toad.

Pablo Picasso zvertavshis to the geologists of our land with the passage of vivchita stocks of Volkonsky, which gives the farb a unique fresh tone. In the Danish hour, the method of otrimannya of the piece Volkonsky has been broken up. Quite simply, according to the data of the occasional past, the Russian iconographers have taken the Farbi from the material in the middle of the century, back to the last "official" view. Due to its popularity among artists, the greens of Ginє (fired in 1837), a chromoform like hydroxide to chromium oxide Cr 2 O 3 * (2-3) H 2 O, were chemically tied, and part of the part was adsorbed. Tsei pіgment nadaє farbі smaragdovogo vіdtіnku.

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VALUE

Chromium of seams in the fourth period of the VI group of the bitwise (B) of the Periodic table. Designated - Cr. The viglyadi of simple speech - siruvato-bili shining metal.

Chromium has the structure of a volume-centered cubic lattice. The strength is 7.2 g / cm3. Melting and boiling temperatures up to 1890 o W and 2680 o S ascertained.

Chromium oxidation step at spoluks

Chromium can be used for metal, and the steps of oxidation of metals in an elementary mill are used. zero, splinters of rosters of electronic gustini in some equally.

Oxidation stages (+2) і (+3) chromium appears in oxides (Cr +2 O, Cr +3 2 O 3), hydroxides (Cr +2 (OH) 2, Cr +3 (OH) 3), halogenides (Cr +2 Cl 2, Cr +3 Cl 3 ), sulfates (Cr +2 SO 4, Cr +3 2 (SO 4) 3) and ін. z'єdnannyah.

Chromium is also characterized by oxidation steps. (+6) : Cr +6 O 3, H 2 Cr +6 O 4, H 2 Cr +6 2 O 7, K 2 Cr +6 2 O 7 etc.

Set up tasks

APPENDIX 1

APPENDIX 2

Zavdannya The same step of oxidized phosphorus can be found in the following:

a) Ca 3 P 2 і H 3 PO 3;

b) KH 2 PO 4 and KPO 3;

c) P 4 O 6 і P 4 O 10;

d) H 3 PO 4 and H 3 PO 3.
Decision In order to ensure that the correct response is given on the delivery of food by hand, there are steps of oxidized phosphorus in the skin steam.

a) The stage of oxidized calcium is (+2), acid and water - (-2) and (+1), apparently. Acceptable level of oxidation of phosphorus for "x" and "y" in proponated halves:

3 × 2 + x × 2 = 0;

3 + y + 3 × (-2) = 0;

The view is incorrect.

b) The stage of oxidized calories is (+1), acid and water - (-2) and (+1), apparently. Acceptable level of chlorine oxidation for "x" and "y" in proponated halves:

1 + 2 × 1 + x + (- 2) × 4 = 0;

1 + y + (-2) 3 = 0;

Відповідь вірна.
View Option (b).

Chromium is an element of the secondary group of the 6th group of the 4th period of the periodic system of chemical elements D.I. Mendeleev, with atomic number 24. Signed by the symbol Cr (Latin Chromium). A simple word is chrome-hard metal blakit-white color.

Chemistry of power to chromium

For the wicked minds, chromium reacts with fluorine. For high temperatures (up to 600 ° C), there is acid, halogens, nitrogen, silicon, boron, sirkoyu, phosphorus.

4Cr + 3O 2 - t ° → 2Cr 2 O 3

2Cr + 3Cl 2 - t ° → 2CrCl 3

2Cr + N 2 - t ° → 2CrN

2Cr + 3S - t ° → Cr 2 S 3

A roasted plant reacts with water vapor:

2Cr + 3H 2 O → Cr 2 O 3 + 3H 2

Chromium breaks down in dilutions of strong acids (HCl, H 2 SO 4)

At the end of the day, Cr 2+ salts are accepted, and in some cases - Cr 3+ salts.

Cr + 2HCl → CrCl 2 + H 2

2Cr + 6HCl + O 2 → 2CrCl 3 + 2H 2 O + H 2

The presence of oxidized oxide on the surface of the metal explains the passivity in relation to the rate of concentration of acids - oxidizing acids.

Z'єdnannya chrome

Chromium (II) oxide that chromium (II) hydroxide may have a basic character.

Cr (OH) 2 + 2HCl → CrCl 2 + 2H 2 O

Chromium spoluces (II) - strong cousins; go over to chrome (III) in spoluca before every day.

2CrCl 2 + 2HCl → 2CrCl 3 + H 2

4Cr (OH) 2 + O 2 + 2H 2 O → 4Cr (OH) 3

Chromium oxide (III) Cr 2 O 3 - greens, non-destructive powder from water. You can also be discouraged when fried with chromium (III) hydroxide or dichromates in calcium and ammonia:

2Cr (OH) 3 - t ° → Cr 2 O 3 + 3H 2 O

4K 2 Cr 2 O 7 - t ° → 2Cr 2 O 3 + 4K 2 CrO 4 + 3O 2

(NH 4) 2 Cr 2 O 7 - t ° → Cr 2 O 3 + N 2 + 4H 2 O (reaction "vulcan")

Amphoteric oxide. When Cr 2 O 3 is fused in meadows, soda and acidic salts, half-chrome occurs with an oxidation step (+3):

Cr 2 O 3 + 2NaOH → 2NaCrO 2 + H 2 O

Cr 2 O 3 + Na 2 CO 3 → 2NaCrO 2 + CO 2

When fused from the sum of the meadows and oxidizing agent, wash off the halves with chromium in the oxidation stage (+6):

Cr 2 O 3 + 4KOH + KClO 3 → 2K 2 CrO 4 + KCl + 2H 2 O

Chromium (III) hydroxide r (ВІН) 3. Amphoteric hydroxide. Syro-greens, spread out when heated, consuming water and setting greens metagidroxid CrO (BIN). Chi does not differ from water. There is a chance to settle down at the viglyadі siro-blakitnoy and blakit-green hіdratu. React with acids and meadows, not in conjunction with ammonia hydrate.

Ma amphoternі power - to distinguish yak from acids, so in meadows:

2Cr (OH) 3 + 3H 2 SO 4 → Cr 2 (SO 4) 3 + 6H 2 O Cr (OH) 3 + DN + = Cr 3+ + 3H 2 O

Cr (OH) 3 + KOH → K, Cr (OH) 3 + ZOH - (conc.) = [Cr (OH) 6] 3-

Cr (OH) 3 + KOH → KCrO 2 + 2H 2 O Cr (OH) 3 + MOH = MCrO 2 (green) + 2H 2 O (300-400 ° C, M = Li, Na)

Cr (OH) 3 →(120 o C – H 2 O) СrO (ВІН) → (430-1000 0 С -H 2 O) Cr 2 O 3

2Сr (ОН) 3 + 4NаОН (conc.) + DN 2 O 2 (conc.) = 2Na 2 СrO 4 + 8Н 2 0

Otrimannya: precipitation with amiaku hydrate from the range of chromium (III) salts:

Cr 3+ + 3 (NH 3 H 2 O) = Zr(ВІН) 3 ↓+ Optic nerve disc 4+

Cr 2 (SO 4) 3 + 6NaOH → 2Cr (OH) 3 ↓ + 3Na 2 SO 4

Salt chromium (III) may be violet or dark green. per cheeky authorities nagaduyut without barvnі salts alumіnіyu.

Cr (III) spoludes can be oxidative and non-oxidizing:

Zn + 2Cr +3 Cl 3 → 2Cr +2 Cl 2 + ZnCl 2

2Cr +3 Cl 3 + 16NaOH + 3Br 2 → 6NaBr + 6NaCl + 8H 2 O + 2Na 2 Cr +6 O 4

Z'єdannya hexavalent chromium

Chromium (VI) oxide CrO 3 - yaskravo-chervonі crystals, rozchinnі near water.

Dissolve with chromate (or dichromate) calcium and H 2 SO 4 (conc.).

K 2 CrO 4 + H 2 SO 4 → CrO 3 + K 2 SO 4 + H 2 O

K 2 Cr 2 O 7 + H 2 SO 4 → 2CrO 3 + K 2 SO 4 + H 2 O

CrO 3 is an acidic oxide, in the meadows I solidify chromate CrO 4 2-:

CrO 3 + 2KOH → K 2 CrO 4 + H 2 O

In the sour middle, chromate is transformed into orange dichromate Cr 2 O 7 2-:

2K 2 CrO 4 + H 2 SO 4 → K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O

In the middle of the line, the reaction is opposite to the opposite direction:

K 2 Cr 2 O 7 + 2KOH → 2K 2 CrO 4 + H 2 O

Calcium dichromate - oxidizes the acidic environment:

Up to 2 Сr 2 O 7 + 4H 2 SO 4 + 3Na 2 SO 3 = Cr 2 (SO 4) 3 + 3Na 2 SO 4 + K 2 SO 4 + 4H 2 O

K 2 Cr 2 O 7 + 4H 2 SO 4 + 3NaNO 2 = Cr 2 (SO 4) 3 + 3NaNO 3 + K 2 SO 4 + 4H 2 O

K 2 Cr 2 O 7 + 7H 2 SO 4 + 6 KI = Cr 2 (SO 4) 3 + 3I 2 + 4K 2 SO 4 + 7H 2 O

K 2 Cr 2 O 7 + 7H 2 SO 4 + 6FeSO 4 = Cr 2 (SO 4) 3 + 3Fe 2 (SO 4) 3 + K 2 SO 4 + 7H 2 O

Calcium chromate Up to 2 Cr About 4 . Oxosol. Zhovty, non-hygroscopic. Melting without folding, heat resistant. Good luck at the water ( zhovta farbuvannya the difference is based on anion of CrO 4 2-), trochas are hydrolyzed according to anion. In the acidic environment, go to 2 Cr 2 O 7. Oxidizing (weak, low K 2 Cr 2 O 7). Enter at the reaction of the ion exchange.

Yakisna reaction on іon CrO 4 2 - vipadannya zhovtoy siege chromate barіyu, sho lay in a strongly acidic environment. Stagnate yak mordant for an hour farbuvannya fabric, tanning agent, selective oxidizing agent, reagent in analytical chemistry.

Equivalent reaction:

2K 2 CrO 4 + H 2 SO 4 (30%) = K 2 Cr 2 O 7 + K 2 SO 4 + H 2 O

2K 2 CrO 4 (t) + 16HCl (kin c., Hot.) = 2CrCl 3 + 3Cl 2 + 8H 2 O + 4KCl

2K 2 CrO 4 + 2H 2 O + 3H 2 S = 2Cr (OH) 3 ↓ + 3S ↓ + 4KOH

2K 2 CrO 4 + 8H 2 O + 3K 2 S = 2K [Cr (OH) 6] + 3S ↓ + 4KOH

2K 2 CrO 4 + 2AgNO 3 = KNO 3 + Ag 2 CrO 4 (worm) ↓

Yakisna reaction:

Up to 2 СгO 4 + Сl 2 = 2КСl + CrO 4 ↓

2СrO 4 (t) + 2HCl (rozb.) = Сr 2 O 7 (p) + С1 2 + Н 2 O

Otrimannya: save chromium with potash on the occasion:

4 (Сr 2 Fe ‖‖) O 4 + 8К 2 CO 3 + 7O 2 = 8К 2 СrO 4 + 2Fе 2 O 3 + 8СO 2 (1000 ° С)

Calcium dichromate K 2 Cr 2 O 7 ... Oxosol. Technical name chromepik... Orange-chervonia, non-hygroscopic. To melt without unfolding, when the heating is too high, to fold. Good luck at the water ( orange farbuvannya the difference between the opinions of the ion Cr 2 O 7 2-). At the puddle center, I will set it up to 2 CrO 4. Typical oxidizing agent at razchinі and when fused. Enter at the reaction of the ion exchange.

Yakisnі reactions- Syn of farbuvannya of an etheric range in the presence of H2O2, a synsofarbuvannya of a water range in the presence of atomic water.

Yak tanning agent stagnates, mordant for farbuvanny fabrics, a component of industrial warehouses, a reagent in analytical chemistry, an inhibitor of corrosion of metals, sums of H 2 SO 4 (conc.) - for mild chemical dishes.

Equivalent reaction:

4K 2 Cr 2 O 7 = 4K 2 CrO 4 + 2Cr 2 O 3 + 3O 2 (500-600 o C)

K 2 Cr 2 O 7 (t) + 14HCl (kin c) = 2CrCl 3 + 3Cl 2 + 7H 2 O + 2KCl (boiling point)

K 2 Cr 2 O 7 (t) + 2H 2 SO 4 (96%) ⇌2KHSO 4 + 2CrO 3 + H 2 O (“chromova sumish”)

K 2 Cr 2 O 7 + KOH (fin) = H 2 O + 2K 2 CrO 4

Cr 2 O 7 2- + 14H + + 6I - = 2Cr 3+ + 3I 2 ↓ + 7H 2 O

Cr 2 O 7 2- + 2H + + 3SO 2 (g) = 2Cr 3+ + 3SO 4 2- + H 2 O

Cr 2 O 7 2- + H 2 O + 3H 2 S (g) = 3S ↓ + 2OH - + 2Cr 2 (OH) 3 ↓

Cr 2 O 7 2- (conc.) + 2Ag + (pink.) = Ag 2 Cr 2 O 7 (t. Chervonia) ↓

Cr 2 O 7 2- (loose) + H 2 O + Pb 2+ = 2H + + 2PbCrO 4 (chervonia) ↓

K 2 Cr 2 O 7 (s) + 6HCl + 8H 0 (Zn) = 2CrCl 2 (syn) + 7H 2 O + 2KCl

Otrimannya: processing Up to 2 СrO 4 with sirchanic acid:

2K 2 CrO 4 + H 2 SO 4 (30%) = Up to 2Cr 2 O 7 + Up to 2 SO 4 + H 2 O

Purpose: poglybiti knowledge of studies on the topic of employment.

Zavdannya:

  • give a description of the lame yak simple speech;
  • learn about chrome oxidation step;
  • show the abundance of power from half to the oxidation step;
  • indications of oxidatively - inert power with chromium;
  • to continue the formulation of mines scientists to record the chemical reactions in the molecular and ionic viewer, to fold the electronic balance;
  • Continue the formulation in the space of a chemical experiment.

Employment form: lecture with elements independent robots studies and cautions for a chemical experiment.

Go busy

I. Repetition of the material before the front occupation.

1. Please refer to the power supply of the device:

What elements do you need to stick to chrome?

Write electronic formulas of atoms

What type of elements should be placed?

Do you have any oxidized steps on the side?

How can I change the radioactive atom and the energy of ionization from chromium to tungsten?

You can propose to memorize the scientists memorize the table, vikoristovuchi tabular values ​​of the radii of atoms, the energy of the ionization and the growth of the visnovka.

See tables:

2. Hearings about the study on the topic "Elementy pidgruppi lame in nature, rejecting and storing."

II. lecture.

Lecture plan:

  1. Chromium.
  2. Spoluki chrome. (2)
  • Chromium oxide; (2)
  • Chromium hydroxide. (2)
  1. Spoluki chrome. (3)
  • Chromium oxide; (3)
  • Chromium hydroxide. (3)
  1. Z'єdnannya chrome (6)
  • Chromium oxide; (6)
  • Chromic and dichromic acid.
  1. Deposits of power from half to chrome are from the oxidation step.
  2. Oxidized - as is the main power of chromium.

1. Chrome.

Chromium is a bright, bright metal, even hard (thickness 7, 2 g / cm 3), melting temperature 1890C.

Cheerful authorities: chrome for inactive minds of inactive metal. We are covering the surface with an oxide layer (Cr 2 Pro 3). When heated, the oxide melt collapses, and chromium reacts with simple words for high temperatures:

  • 4Сr + 3О 2 = 2Сr 2 Pro 3
  • 2Сr + 3S = Сr 2 S 3
  • 2Сr + 3Cl 2 = 2СrСl 3

Zavdannya: lining of r_vnyannya reactions of chromium with nitrogen, phosphorus, carbon and silicon; up to one from the level of the electronic balance, in addition to the oxidation and the reference.

Vzaєmodiya chrome with folding tongues:

At even higher temperatures, chromium reacts with water:

  • 2Сr + 3 Н 2 О = Сr 2 Pro 3 + 3Н 2

Zavdannya:

Chromium reacts with diluted hydrochloric acid and hydrochloric acids:

  • Сr + Н 2 SO 4 = СrSО 4 + Н 2
  • Cr + 2HCl = CrCl 2 + H 2

Zavdannya: in the area of ​​the electronic balance, in order to oxidize and maintain.

Concentration of hydrochloric acid and nitric acid and passivate chromium.

2. Z'єdnannya chrome. (2)

1. Chromium oxide (2)- CrO - solid yaskravo - chervona rechovina, a typical basic oxide (yomu form hydroxide to chromium (2) - Cr (OH) 2), does not break down in water, it does not work out in acids:

  • CrO + 2HCl = CrCl 2 + H 2 O

Zavdannya: In the case of a specific reaction in the molecular and ionic vividly in the interaction between chromium oxide (2) and sirchanic acid.

Chromium (2) oxide is easily oxidized on dry:

  • 4СrО + Pro 2 = 2Сr 2 Pro 3

Zavdannya: in the area of ​​the electronic balance, in order to oxidize and maintain.

Chromium oxide (2) is established when chromium oxidized with amalgam is acidic:

2Сr (amalgam) + О 2 = 2СrО

2. Chromium hydroxide (2)- Сr (ОН) 2 - the spine of the same coloru, it is rotten in water, because of its basic character, due to the acids:

  • Cr (OH) 2 + H 2 SO 4 = CrSO 4 + 2H 2 O

Zavdannya: in the area of ​​similar reactions in molecular and ionic viglyadі in the interchange of chromium oxide (2) with hydrochloric acid.

Yak and chromium oxide (2), chromium hydroxide (2) oxidize:

  • 4 Cr (OH) 2 + O 2 + 2H 2 O = 4Cr (OH) 3

Zavdannya: in the area of ​​the electronic balance, in order to oxidize and maintain.

Otrimati hydroxide to chromium (2) can be done with diya meadows on salt chromium (2):

  • CrCl 2 + 2KOH = Cr (OH) 2 ↓ + 2KCl

Zavdannya:іонні рівняння.

3. Z'єdnannya chrome. (3)

1. Chromium oxide (3)- Cr 2 Pro 3 - powder of a dark green color, non-sensitive to water, refractory, close to corundum in hardness (yom type hydroxide to chromium (3) - Cr (OH) 3). Chromium (3) oxide is of a mamphoteric character, however, acids and meadows tend to be rotten. Reactions from meadows to go when rafting:

  • Cr 2 Pro 3 + 2KON = 2KSrO 2 (kulgaє Do)+ H 2 Pro

Zavdannya: in the area of ​​an equal reaction in the molecular and ionic vivid in the interaction between chromium oxide (3) and hydroxide lithium.

With concentrated solutions of acids and lugs, it is important to:

  • Cr 2 Pro 3 + 6 KOH + 3H 2 O = 2K 3 [Cr (OH) 6]
  • Cr 2 Pro 3 + 6HCl = 2CrCl 3 + 3H 2 O

Zavdannya: in the area of ​​similar reactions in molecular and ionic viglyadi in the interaction of chromium oxide (3) with concentrated sirchanic acid and concentrated sodium hydroxide.

Chromium oxide (3) can be removed when applied to ammonium dichromate:

  • (NH 4) 2Cr 2 Pro 7 = N 2 + Cr 2 Pro 3 + 4H 2 Pro

2. Chromium hydroxide (3) Cr (OH) 3 can be distilled with chromium salts (3):

  • СrСl 3 + 3КОН = Сr (ОН) 3 ↓ + 3КСl

Zavdannya:іонні рівняння

Chromium hydroxide (3) є siege siro-green koloru, when it is rejected, the meadow needs brethren in instability. Otrimany in such a way hydroxide to chromium (3), on the form of a kind of oxide, easily interacts with acids and meadows, tobto. vyavlya amphoteric powers:

  • Cr (OH) 3 + 3HNO 3 = Cr (NO 3) 3 + 3H 2 O
  • Cr (OH) 3 + 3KON = K 3 [Cr (OH) 6] (hexahydroxochromite K)

Zavdannya: in the area of ​​similar reactions in the molecular and ionic viglyadi in the interaction of chromium hydroxide (3) with hydrochloric acid and sodium hydroxide.

When Cr (OH) 3 is fused, metachromies and orthochromies occur in meadows:

  • Cr (OH) 3 + KOH = KCrO 2 (metachromite K)+ 2H 2 O
  • Cr (OH) 3 + KOH = K 3 CrO 3 (orthochrome K)+ 3H 2 O

4. Z'єdnannya chrome. (6)

1. Chromium oxide (6)- СrО 3 - dark - red crystal speech, good in water - typical acidic oxide. Whole oxide forms two acids:

  • СrО 3 + Н 2 О = Н 2 СrО 4 (chromic acid - pretend with excess water)
  • CrO 3 + H 2 O = H 2 Cr 2 Pro 7 (Dichromic acid - to establish itself at a high concentration of chromium oxide (3)).

Chromium oxide (6) is an even strong oxidizing agent, therefore, it is energetically interrelated with organic fluids:

  • З 2 Н 5 ВІН + 4СrО 3 = 2СО 2 + 2Сr 2 Pro 3 + 3Н 2 О

Oxidized also iodine, sirku, phosphorus, vugilya:

  • 3S + 4CrO 3 = 3SO 2 + 2Cr 2 O 3

Zavdannya: Rivnyannya store chemical reactions chromium (6) oxide with iodine, phosphorus, vugillam; up to one level of the area electronic balance

When heated up to 250 0 С chromium oxide (6) will decompose:

  • 4CrO 3 = 2Cr 2 O 3 + 3O 2

Chromium oxide (6) can be trimmed with concentrated hydrochloric acid on solid chromate and dichromate:

  • Up to 2 Cr 2 Pro 7 + H 2 SO 4 = Up to 2 SO 4 + 2CrO 3 + H 2 O

2. Chromic and dichromic acid.

Chromic and dichromic acids are removed only at water levels, setting up strong salts, such as chromate and dichromate. Chromati and їkh rozchini maut zhovte zhovte barvlennya, dichromati - orange.

Chromate - іoni CrO 4 2- і dichromate - іoni Cr 2O 7 2- it is easy to change one into one when changing the middle of the range

In sour middle ground, the chromate range goes over to dichromate:

  • 2К 2 СrО 4 + Н 2 SO 4 = К 2 Сr 2 О 7 + К 2 SO 4 + Н 2 О

In the puddle middle, dichromati goes over to chromati:

  • Up to 2 Cr 2 Pro 7 + 2KON = 2K 2 CrO 4 + H 2 O

When diluted, dichromic acid is converted to chromic acid:

  • H 2 Cr 2 O 7 + H 2 O = 2H 2 CrO 4

5. Degree of power from half to chrome from the oxidation step.

Oxidation step +2 +3 +6
Oxide CrO Cr 2 Pro 3 CrO 3
The nature of the oxide Main amphoteric acidic
Hydroxide Cr (OH) 2 Cr (OH) 3 - H 3 CrO 3 H 2 CrO 4
The nature of the hydroxide Main amphoteric acidic

→ weakening of the main powers and strengthening of acidic ones →

6. Oxidic - inert power with chromium.

Reactions in the acidic environment.

In the acidic middle, the Сr +6 half pass to the Сr + 6 half;

  • Up to 2 Cr 2 Pro 7 + 3H 2 S + 4H 2 SO 4 = 3S + Cr 2 (SO 4) 3 + K 2 SO 4 + 7H 2 O
  • S -2 - 2e → S 0
  • 2Cr +6 + 6e → 2Cr +3

Zavdannya:

1. The level of measurement of the reaction by the method of electronic balance, in addition to oxidizing the following:

  • Na 2 CrO 4 + K 2 S + H 2 SO 4 = S + Cr 2 (SO 4) 3 + K 2 SO 4 + Na 2 SO 4 + H 2 O

2. To add the reaction products, the level of level to the level of the electronic balance method, add the oxidizing agent:

  • K 2 Cr 2 O 7 + SO 2 + H 2 SO 4 =? +? + H 2 Pro

Reactions at the puddle middle.

At the puddle center, chromium Cr +3 passes over to the half of Cr +6 for oxidation: J2, Br2, Cl2, Ag2O, KClO3, H2O2, KMnO4:

  • 2KCrO 2 +3 Br 2 + 8NaOH = 2Na 2 CrO 4 + 2KBr + 4NaBr + 4H 2 O
  • Cr +3 - 3e → Cr +6
  • Br2 0 + 2e → 2Br -

Zavdannya:

Achievement of the level of reaction by the method of electronic balance, in addition to oxidizing the following:

  • NaCrO 2 + J 2 + NaOH = Na 2 CrO 4 + NaJ + H 2 O

Add the products of the reaction, the level of education by the method of electronic balance, use the oxidizing agent:

  • Cr (OH) 3 + Ag 2 O + NaOH = Ag +? +?

In such a rank, oxidizing power is lastly accepted through the change of oxidation steps in the series: Cr +2 → Cr +3 → Cr +6. Z'єdnannya chromium (2) - strong іdnovniki, scho easily oxidized, transformed to chrome spoluks (3). Chromium (6) - strong oxidizing, which is easy to introduce into chromium (3). Chromium (3), in the case of interaction with strong precursors, is oxidizing power, turning into chromium (2), and in case of interaction with strong oxidizing agents, it appears in the presence of chromium (6)

Before the methodology of the lecture:

  1. For activization educational performance study and educate interest, docily for an hour of the lecture to conduct a demonstration experiment. Here you can demonstrate to the scientists the following about the possibilities of the initial laboratory:
  • possession of chromium oxide (2) and chromium hydroxide (2), proof of the main powers;
  • possession of chromium oxide (3) and chromium hydroxide (3), proof of amphoteric powers;
  • Obtaining chromium oxide (6) and reducing it from water (removing chromium and dichromic acids);
  • transition chromates from dichromates, dichromates from chromate.
  1. The management of independent robots is possible to differentiate from the level of real primary capabilities of scientists.
  2. The lecture can be completed by the victories of the offensive buildings: write down the vernacular chemical reactions, for the help of which it is possible to make the offensive revision:

.III. Home zavdannya: add some lectures (add some chemistry reactions)

  1. Vasil'va Z.G. Laboratory robots from foreign and non-organic chemistry. -M .: "Khimiya", 1979 - 450 p.
  2. Єgorov A.S. Physics tutor. - Rostov-on-Don: "Fenix", 2006.-765 p.
  3. Kudryavtsev O.O. Skladannya cheeky rivnyans... - M., "Vishcha school", 1979. - 295 p.
  4. Petrov M.M. Inorganic chemistry. - Leningrad: "Khimiya", 1989. - 543 p.
  5. Ushkalova V.M. Хімія: competition and presentation. - M .: "Osvita", 2000. - 223 p.
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