(iv) Ammonium hydroxide is added to zinc nitrate solution, first little & then excess.
state the observation

its a displacement reaction
i can say it
i cannot help you furthur as i forgot
i want the observation when this reaction takes place
i think it is the white .ppt formed which is soluble in excess.


Zn(NO3)2     +     2 NH4OH      ----------------------->     Zn(OH)2  +  2 NH4NO3
                                                                            white ppt.
on adding a little NH4OH we get white precipitate. 

in excess of NH4OH

Zn(OH)2   +   NH4OH   ----------------------->  [Zn(NH3)4]2+
                                                        colourless solution, soluble 
on adding excess of NH4OH, Zn(OH)2  get dissolve in NH4OH and we get colourless solution.