Which of the following compounds exist, or do both of them exist? What are their names?

(a) #Hg(CNS)#
(b) #Hg(CNS)_2#

1 Answer
Mar 11, 2016

Answer:

#"Hg"("SCN")_2#

Explanation:

The compound given to you in option (b) exists and it's called mercury(II) thiocyanate.

It contains the mercury(II) cation, #"Hg"^(2+)#, and the thiocyanate anion, #"SCN"^(-)#. Notice that the thiocyanate anion carries a #1-# charge, which is why you need two of them to balance the #2+# charge of the mercury(II) cation.

https://en.wikipedia.org/wiki/Mercury%28II%29_thiocyanate

Mercury(II) thiocyanate is quite famous because its thermal decomposition causes an effect called the Pharaoh's Serpent.

Basically, the reaction, which is highly toxic, by the way, forms a brownish column that keeps growing as the reaction proceeds.

A detailed description of the decomposition reaction can be seen here