Question

State the effect of adding a small amount of : (a) sodium hydroxide (b) ammonium hydroxide followed by an excess in case to samples of the salt solutions.
Zinc nitrate [ small amount ________ in excess ________]

Answer 1

Zinc nitrate :
a. with sodium hydroxide :

• \[\ce{Zn(NO3) + 2NaOH -> Zn(OH)2 + 2NaNO3}\]
• On addition of excess of NaOH, white ppt. of Zn(OH)₂ dissolves.

b. With ammonium hydroxide :

• \[\ce{Zn(NO3) + 2NH4OH -> Zn(OH)2 + 2NH4NO3}\]
• The gelatinous white insoluble ppt. of Zn(OH)₂ dissolves in excess of ammonium hydroxide.