Question

State two relevant observations:

(a) Ammonium hydroxide solution is added to copper(II) nitrate solution in small quantities and then in excess.

Answer 1

The observations are as follows:

When ammonium hydroxide $\left({\mathrm{NH}}_4\mathrm{OH}\right)$ is added to copper nitrate solution $\left(\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\right)$ ,then a pale blue colored precipitate of copper hyroxide$\left(\mathrm{Cu}{\left(\mathrm{OH}\right)}_2\right)$ is formed.

• The reaction can be represented as:

$\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2{\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)\to \mathrm{Cu}{\left(\mathrm{OH}\right)}_2\downarrow +2{\mathrm{NH}}_4{\mathrm{NO}}_3\left(\mathrm{aq}\right)$

• This precipitate turns into a deep inky blue color by adding excess ammonium hydroxide solution.