Which formula represents potassium chromate?

Potassium chromate is represented by the formula K2CrO4. This compound includes two potassium ions (K+), one chromium ion (Cr is in the +6 oxidation state as part of the chromate ion), and four oxide ions (O2-).

In the chromate ion, CrO4^2-, the chromium is in a +6 oxidation state, and the overall charge of the ion is -2. To balance this charge when combining with potassium, which has a +1 charge, two potassium ions are needed, leading to the formula K2CrO4.

This formula indicates the stoichiometric ratio of the components in the compound, aligning correctly with the known oxidation states and chemical structure of potassium chromate.

The other formulations provided do not accurately reflect this balance of ions or the stoichiometry associated with potassium chromate. For instance, K2Cr2O7 represents potassium dichromate, which has a different structure and composition, as it contains two chromium atoms in the formula. Meanwhile, KCrO4 does not provide the correct number of potassium ions to maintain the charge balance, and K3CrO8 represents a compound that does not correspond to the known chemistry of chromates.