In salts of polyatomic anion, as polarising power of cation increases, thermal stability of the salt — d and f Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: The conversion between chromate (CrO4^2-) and dichromate (Cr2O7^2-) is pH-dependent. Chromate is stable in basic/neutral conditions, while dichromate is stable in acidic conditions. Step 2: Increasing acidity (lowering pH to an acidic value, x < 7, e.g., 6) converts yellow chromate to orange dichromate: 2CrO4^2- + 2H+ <=> Cr2O7^2- + H2O. Conversely, adding base (raising pH to a basic value, y > 7, e.g., 8) shifts the equilibrium back to chromate. Step 3: Thus, x must be acidic (6) and y must be basic (8), which corresponds to option (a).