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Which of the following compounds turns black upon reaction with \mathrm{NH}_{4} \mathrm{OH} ?

Option: 1

Lead chloride


Option: 2

Mercurous chloride


Option: 3

Mercuric chloride


Option: 4

Silver chloride


Answers (1)

best_answer

As we have learnt, 

Mercurous Chloride \mathrm{(Hg_2Cl_2)} is white in color. Upon reaction with \mathrm{NH_4OH}, it disproportionates to form Mercuric Amido Chloride \mathrm{(NH_2HgCl)} and Mercury \mathrm{(Hg)} which appears black in colour 

\mathrm{Hg _{2} Cl _{2}+2 NH _{4} OH \rightarrow \underset{(Mercuric\ Amido \ Chloride)}{NH _{2}- Hg - Cl} +\underset{\text { (Black ppt) }}{ Hg }+ NH _{4} Cl +2 H _{2} O}

Hence, the correct answer is Option (2)

Posted by

Divya Prakash Singh

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