Question

Describe the extraction of mercury metal from its ore Cinnabar ($HgS$).

Answer 1

Hint: Try to recall that metals like mercury, lead are being extracted from their sulphide ore by the method of self-reduction or auto reduction. Now, by using this you can easily answer the given question.

Complete Solution:
- We know that auto-reduction or self-reduction is a very popular method for extraction of less electropositive metals like mercury, lead etc. from their sulphide ore.
- It is a process in which sulphide ores of less electropositive metals like Hg, Pb, Cu etc. are heated in air so as to convert part of the ore into oxide or sulphate which then reacts with remaining of sulphide ore in absence of air to give the metal and sulphur dioxide.
- Since, no external reducing agent is used in this process that is why it is referred to as auto reduction or self-reduction.
- The reactions which occur in the extraction of mercury metal from its ore cinnabar ($HgS$) are as follows:
\[\begin{align}
& 2HgS+3{{O}_{2}}\to 2HgO+2S{{O}_{2}} \\
& 2HgO+HgS\to 3Hg+S{{O}_{2}} \\
\end{align}\]

- The mercury which is obtained by the self-reduction process is not very pure. So, they undergo refining to get their pure form.
- The method used for refining of mercury metal is distillation. This method is useful for metals like mercury which have low boiling point.

Note: Note that distillation is based on the difference in boiling point of metal and impurities. Metals should have low boiling point and impurities should have high boiling point. In the distillation method, the impure metal is evaporated to obtain pure metal as distillate.