Question

How will you distinguish between lead nitrate and zinc nitrate solution with the help of ammonium hydroxide solution? Explain with equation.

Answer 1

Distinguish between lead nitrate and zinc nitrate solution with the help of ammonium hydroxide solution

• Different chemical compounds will react with the same reagent to give different products.
• This is seen when Lead nitrate $\left[\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\right]$ and Zinc nitrate $\left[\mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2\right]$ react with Ammonium hydroxide $\left({\mathrm{NH}}_4\mathrm{OH}\right).$
• When Lead nitrate reacts with an excess of Ammonium hydroxide it will produce a white precipitate $\left[\mathrm{Pb}{\left(\mathrm{OH}\right)}_2\right]$ which is insoluble in Ammonium hydroxide. The reaction is given as follows:

$$\begin{gathered} \mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2+2{\mathrm{NH}}_4\mathrm{OH}\to \mathrm{Pb}{\left(\mathrm{OH}\right)}_2+2{\mathrm{NH}}_4{\mathrm{NO}}_3 \\ \mathrm{Lead}\mathrm{nitrate}\mathrm{Ammonium}\mathrm{hydroxide}\mathrm{Lead}\left(\mathrm{II}\right)\mathrm{oxide}\mathrm{Ammonium}\mathrm{nitrate} \end{gathered}$$

• However, when Zinc nitrate reacts with Ammonium hydroxide, the precipitate $\left[\mathrm{Zn}{\left(\mathrm{OH}\right)}_2\right]$ obtained is soluble in excess of ammonium hydroxide. The reaction is shown as follows:

$$\begin{gathered} \mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2+2{\mathrm{NH}}_4\mathrm{OH}\to \mathrm{Zn}{\left(\mathrm{OH}\right)}_2+2{\mathrm{NH}}_4{\mathrm{NO}}_3 \\ \mathrm{Zince}\mathrm{nitrate}\mathrm{Ammonium}\mathrm{hydroxide}\mathrm{Zinc}\mathrm{hydroxide}\mathrm{Ammonium}\mathrm{nitrate} \end{gathered}$$

When Lead nitrate and Zinc nitrate react with Ammonium hydroxide, then the prior forms precipitate soluble in Ammonium hydroxide solution, whereas the latter forms insoluble precipitate.