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The hydrogen chromate ion may be protonated, with the formation of molecular chromic acid, H 2 CrO 4, but the pK a for the equilibrium H 2 CrO 4 ⇌ HCrO − 4 + H + is not well characterized. Reported values vary between about −0.8 and 1.6. [4] The dichromate ion is a somewhat weaker base than the chromate ion: [5]
In 2005–06, potassium dichromate was the 11th-most-prevalent allergen in patch tests (4.8%). [12] Potassium dichromate is one of the most common causes of chromium dermatitis; [13] chromium is highly likely to induce sensitization leading to dermatitis, especially of the hand and forearms, which is chronic and difficult to treat ...
Chromate and dichromate have equal concentrations. Setting [CrO 2− 4] equal to [Cr 2 O 2− 7] in Eq. 3 gives [CrO 2− 4] = 1 / β 2 [H +] 2 . The predominance diagram is interpreted as follows. The chromate ion is the predominant species in the region to the right of the green and blue lines. Above pH ~6.75 it is always the ...
Structure of CrO(O 2) 2 (pyridine).Hydrogen atoms bonded to carbon atoms are omitted. Color code: Cr = gray, C= black, H = white, O= red, N = blue. Chromium(VI) oxide peroxide is formed by the addition of acidified hydrogen peroxide solutions to solutions of metal chromates or dichromates, such as sodium chromate or potassium dichromate.
Sodium dichromate is the inorganic compound with the formula Na 2 Cr 2 O 7. However, the salt is usually handled as its dihydrate Na 2 Cr 2 O 7 ·2 H 2 O . Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. [ 1 ]
Chromic acid is jargon for a solution formed by the addition of sulfuric acid to aqueous solutions of dichromate. It consists at least in part of chromium trioxide. [3] The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium ...
Chromium trioxide is generated by treating sodium dichromate with sulfuric acid: [6] H 2 SO 4 + Na 2 Cr 2 O 7 → 2 CrO 3 + Na 2 SO 4 + H 2 O. Approximately 100,000 tonnes are produced annually by this or similar routes. [7] The solid consists of chains of tetrahedrally coordinated chromium atoms that share vertices.
Chromium(III) can be obtained by dissolving elemental chromium in acids like hydrochloric acid or sulfuric acid, but it can also be formed through the reduction of chromium(VI) by cytochrome c7. [9] The Cr 3+ ion has a similar radius (63 pm) to Al 3+ (radius 50 pm), and they can replace each other in some compounds, such as in chrome alum and alum.