Question

When ammonium hydroxide is added to solution B, a dirty green precipitate is formed.


i. What will happen to this precipitate in excess ammonium hydroxide?


ii. What is the cation in the solution B ?​

Answer 1

Answer:

The answer is option  (A).  Cation A is Fe  

2+

 as it gives green coloured precipitate of ferrous hydroxide when reacted with  NH  

4

​  

OH . When NH  

4

​  

OH is added to a solution of Fe  

3+

ions it results in the formation of ferric hydroxide which is reddish brown in colour.Hence cation B is Fe  

3+

. When NH  

4

​  

OH is added to a solution of copper ions the copper ions will react with the few OH  

−

 to make insoluble Cu(OH)  

2

​  

. The solid exists in a suspension. As more NH  

4

​  

OH is added the insoluble Cu(OH)  

2

​  

 will dissolve as [Cu(NH  

3

​  

)  

4

​  

]  

2+

 is formed. The copper-ammonia complex ion is a deep purple, and it will be difficult to see through the solution, but there won't be any solid precipitate remaining. Thus the cation C is Cu  

2+

Explanation: