Question

A compound which is insoluble in cold water but soluble in excess of ammonia solution is:
(a)- Sulfur
(b)- Sulfate
(c)- Silver chloride
(d)- Hydrogen chloride

Answer 1

A compound that is soluble in excess of ammonia solution but insoluble in cold water is a compound of a noble metal. This compound can make coordination compounds with ammonia.

Complete step by step answer:
The compound that is soluble in excess of ammonia solution but insoluble in cold water is a compound of a noble metal. So, in the options above given, silver chloride is the compound of noble metal silver.
Silver is an element that belongs to the d-block, so it has the ability to form a coordination compound. So when the silver chloride is dissolved in water the silver chloride will split into ions i.e., silver cation and chloride anion. As water is not a suitable ligand for the formation of coordination with silver cation. But when silver chloride is dissolved in an ammonia solution, the ammonia molecules will form a coordination compound with silver ion having formula ${{[Ag{{(N{{H}_{3}})}_{2}}]}^{+}}$. This property makes the silver chloride dissolve in ammonia solution but not in water.
The color of silver chloride is white and is solid. ${{[Ag{{(N{{H}_{3}})}_{2}}]}^{+}}$ is known as silver diamine cation and the oxidation state of silver is +1.
So, the correct answer is “Option C”.

Note: Silver chloride is not only insoluble in water but it is also insoluble in alcohol and dilute acidic solutions. But it is soluble in concentrated hydrochloric acid, concentrated sulfuric acid, alkali cyanide solution, potassium bromide solution, etc.