The yellow color of an aqueous solution of $\mathrm{K}_{2} \mathrm{CrO}_{4}$ changes to red-orange upon the addition of a few drops of HCl. The red-orange complex, the oxidation state of its central element(s), and the origin of its color, respectively, are:
(a)perchlorate ion, +7, charge transfer
(b)chromium chloride, +3, d-d transition
(c)dichromate ion, +6 and +6, charge transfer
(d)chromic acid, +6, charge transfer
Answer
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