NEET Solved Paper 2017 Question 36
Question: $ HgCl _2 $ and $ l _2 $ both when dissolved in water containing $ {l^{-}} $ ions the pair of species formed is
Options:
A) $ Hg _2l _2,{l^{-}} $
B) $ Hgl _2,l_3^{-} $
C) $ Hgl _2,{l^{-}} $
D) $ Hgl_4^{2-},l_3^{-} $
Show Answer
Answer:
Correct Answer: D
Solution:
- In a solution containing $ HgCl _2,l _2 $ and $ {l^{-}}, $ both $ HgC{l _{,}}_2 $ and $ l _2 $ compete for $ {l^{-}}. $ Since formation constant of $ {{[Hgl _4]}^{2-}} $ $ 1.9\times 10^{30} $ which is very large as compared with $ l _3^{-}(K _{f}=700) $
$ \therefore $ $ {l^{-}} $ will preferentially combine with $ HgCl _2. $ $ HgCl _2+2{l^{-}}\to \underset{Red,ppt}{\mathop{Hgl _2\downarrow +2C{l^{-}}}}, $ $ Hgl _2+2{l^{-}}\to \underset{Soluble}{\mathop{{{[Hgl _4]}^{2-}}}}, $
