Question

What is the colour of lead monoxide?

Answer 1

1. Lead monoxide ($\mathrm{PbO}$) is also known as Lead (II) oxide with a molecular mass of $223.20{\mathrm{gmol}}^{-1}$.
2. Lead monoxide is used in the manufacturing of batteries, glass, electric and electronic products etc. and it basically exists in two forms:
3. Litharge: It is a tetragonal crystal at room temperature which is red in colour.
4. Massicot: It is a stable orthorhombic crystal having a yellow colour above $489°\mathrm{C}$.

Lead monoxide is synthesized by three methods:

1. Lead oxidation in the air by using different forms of Lead at different temperatures: ${\mathrm{PbO}}_2\left(\mathrm{s}\right)\stackrel{293°\mathrm{C}}{\to }{\mathrm{Pb}}_{12}{\mathrm{O}}_{19}\left(\mathrm{s}\right)\stackrel{351°\mathrm{C}}{\to }{\mathrm{Pb}}_{12}{\mathrm{O}}_{17}\left(\mathrm{s}\right)\stackrel{375°\mathrm{C}}{\to }{\mathrm{Pb}}_3{\mathrm{O}}_4\left(\mathrm{s}\right)\stackrel{605°\mathrm{C}}{\to }\mathrm{PbO}\left(\mathrm{s}\right)$
2. Thermal decomposition of Lead nitrate and Lead carbonate: $$\begin{gathered} 2\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)\stackrel{∆}{\to }2\mathrm{PbO}\left(\mathrm{s}\right)+4{\mathrm{NO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right) \\ {\mathrm{PbCO}}_3\left(\mathrm{s}\right)\stackrel{∆}{\to }\mathrm{PbO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right) \end{gathered}$$
3. Thermal decomposition of raw Lead ore (Lead sulfide): $2\mathrm{PbS}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{1000°\mathrm{C}}{\to }2\mathrm{PbO}\left(\mathrm{s}\right)+2{\mathrm{SO}}_2\left(\mathrm{g}\right)$

Colour of Lead monoxide:

1. Before heating process: It is a stable red colour compound.
2. After the heating process: It is a meta-stable yellow colour compound. $\mathrm{PbO}{\left(\mathrm{s}\right)}_{\left(\mathrm{Red}\right)}+1.6{\mathrm{kJmol}}^{-1}\stackrel{~500°\mathrm{C}}{\to }\mathrm{PbO}{\left(\mathrm{s}\right)}_{\left(\mathrm{Yellow}\right)}$