An aqueous solution containing 1 mol of HgI2 and 2 mol of NaI is orange in color. On addition of excess NaI, the solution becomes colorless. The orange color reappears on subsequent addition of NaOCl. Explain with equation.
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Solution
The solution having 1 mole of HgI2 and 2 moles of NaI is orange in colour due to the partial solubility of HgI2. On addition of excess NaI, the colourless complex Na2HgI4 is formed.
HgI2+2Nal→Na2HgI4.
The Na2HgI4 on addition of NaOCl oxidizes as . 3Na2HgI4+2NaOCl+2H2O→3HgI2+2Nal3+4NaOH+2NaCl