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[notes 1] The chromate ion is the predominant species in alkaline solutions, but dichromate can become the predominant ion in acidic solutions. Further condensation reactions can occur in strongly acidic solution with the formation of trichromates, Cr 3 O 2− 10, and tetrachromates, Cr 4 O 2− 13. [2]
The reactivity of the chromate anion with silver is lower than with halides (e.g. chlorides) so that in a mixture of both ions, only silver chloride precipitate will form: [9] AgNO 3(aq) + Cl − (aq) + CrO 2− 4(aq) → AgCl (s) + CrO 2− 4(aq) + NO − 3(aq) Only when no chloride (or any halogen) is left will silver chromate form and ...
The color of chemicals is a physical property of chemicals that in most cases comes from the excitation of electrons due to an absorption of energy performed by the chemical. The study of chemical structure by means of energy absorption and release is generally referred to as spectroscopy .
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 predominant species. At pH < 5.89 (pH < pK 1) the hydrogen chromate ion is predominant in dilute solution but the dichromate ion is predominant in more concentrated solutions.
Potassium dichromate, K 2 Cr 2 O 7, is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health.
The structure of nickel chromate is the same as for chromium vanadate, CrVO 4. Crystals have an orthorhombic structure with unit cell sizes a = 5.482 Å, b = 8.237 Å, c = 6.147 Å. The cell volume is 277.6 Å 3 with four formula per unit cell. [5] [7] Nickel chromate is dark in colour, unlike most other chromates which are yellow. [3]
Strontium chromate is approximately 30 times more soluble in water at 100 °C than at room temperature. Therefore, the yellow strontium chromate can be suspended in a hot solution of a soluble sulfate to digest until fully converted to the much less soluble and white strontium sulfate, leaving the chromate or dichromate in solution.
When the pH of the solution is increased by adding an alkaline solution to it, the extent of hydrolysis increases. Measurements of pH or colour change are used to derive the equilibrium constant for the reaction. Further hydrolysis may occur, producing dimeric, trimeric or polymeric species containing hydroxy- or oxy- groups.