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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]
The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate. At yet lower pH values, further condensation to more complex oxyanions of chromium is possible. Both the chromate and dichromate anions are strong oxidizing reagents at low pH ...
Sodium chromate is the inorganic compound with the formula Na 2 CrO 4. It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and deca hydrates . It is an intermediate in the extraction of chromium from its ores.
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.
The oxide is also formed by the decomposition of chromium salts such as chromium nitrate, or by the exothermic decomposition of ammonium dichromate. (NH 4) 2 Cr 2 O 7 → Cr 2 O 3 + N 2 + 4 H 2 O. The reaction has a low ignition temperature of less than 200 °C and is frequently used in “volcano” demonstrations. [8]
pyridinium dichromate (PDC) is the pyridium salt of dichromate, [Cr 2 O 7] 2-. pyridinium chlorochromate (PCC) is the pyridinium salt of [CrO 3 Cl] −. These salts are less reactive, more easily handled, and more selective than Collins reagent in oxidations of alcohols.
The scientific study of the production, distribution and consumption of goods. Effusion In physics and chemistry, effusion is the process in which a gas escapes from a container through a hole of diameter considerably smaller than the mean free path of the molecules. [170] Elastic modulus The amount a material will deform per unit force. Elasticity
Cadmium chromate; Caesium chromate; Calcium chromate; Chromate ester; Chromated copper arsenate; Template:Chromates and dichromates; Chrome orange; Chrome yellow; Chromic acid; Chromium(VI) oxide peroxide