<P> The predominance diagram shows that the position of the equilibrium depends on both pH and the analytical concentration of chromium . The chromate ion is the predominant species in alkaline solutions, but dichromate can become the predominant ion in acidic solutions . </P> <P> Further condensation reactions can occur in strongly acidic solution with the formation of trichromates, Cr O, and tetrachromates, Cr O . All poly oxyanions of chromium (VI) have structures made up of tetrahedral CrO units sharing corners . </P> <P> The hydrogen chromate ion is a weak acid . </P> <Dl> <Dd> HCrO ⇌ CrO + H; pK ≈ 5.9 </Dd> </Dl>

What is the oxidation number of the chromium atom in na2cr2o4