Please tell me the solution of Q 2004 and Q 2005.
Q2004. Sodium hydroxide solution is added first in a small amount, then in excess to the aqueous salt solutions of
  a] copper [II] sulphate b] zinc nitrate c] lead nitrate  d] iron [III] sulphate. State in each case-
  i] the colour of the precipitate when NaOH is added in a small quantity;  
  ii) the nature of precipitate [i.e. soluble or insoluble ] when NaOH is added in excess.
Write balanced equations for - a] Aluminium    b] Zinc - is warmed with NaOH [ caustic soda ] soln.

Q2005. The questions below refers to the following salt solutions listed A to F: A :- Copper nitrate.
            B: Iron [II] sulphate, C : Iron [III] chloride, D : Lead nitrate, E : Magnesium sulphate, F : Zinc chloride.
         i] Which soln. becomes a deep / inky blue colour when excess of ammonium hydroxide is added to it.
        ii] Which solution gives a white precipitate with excess ammonium hydroxide solution.


Dear Student,



a) Copper nitrate 

When alkali metals are dissolved in liquid ammonia, the alkali metal atom readily loses the valence electron. Both the cation and the electron combine with ammonia to form ammoniated cation and ammoniated electron.
M + (x+y)NH3  → [M(NH3)x]+ + [e(NH3)y]-

The ammoniated electron is responsible for the blue colour of the solution. 

b) Magnesium sulphate
MgSO + NH4OH --> Mg(OH)2  + (NH4)2 SO4    

White colour = Magnesium sulphate.
Kindly post remaining query in next thread.


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