Addition of excess potassium iodide solution to a solution of mereuric chloride gives the halide complex

• Correct answer
  A

  tetrahedral $\mathrm{K}_{2}\left[\mathrm{HgI}_{4}\right]$
• B

  trigonal $\mathrm{K}\left[\mathrm{Hg} \mathrm{I}_{3}\right]$
• C

  linear $\mathrm{Hg}_{2} \mathrm{I}_{2}$
• D

  square planar $\mathrm{K}_{2}\left[\mathrm{Hg} \mathrm{Cl}_{2} \mathrm{I}_{2}\right.$

Solution

$\mathrm{HgCl}_{2}+4 \mathrm{KI} \longrightarrow \mathrm{K}_{2}\left[\mathrm{Hg} \mathrm{I}_{4}\right]+2 \mathrm{KCl}$ $\mathrm{Hg}=[\mathrm{Xe}] 4 t^{14}, 5 d^{10} \mathrm{Gs}^{2}$ $$ \mathrm{Hg}^{2+}=[\mathrm{Xe}] 4{ }^{14}, 5 d^{10}, 6 \mathrm{s}^{\circ} $$

Hence, the correct answer is option: 'A'.