Question

What is meant by black ash in chemistry?

Answer 1

Black ash:

• Black ash is the mixture of impure Sodium carbonate $\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$ and Calcium sulfide$\left(\mathrm{CaS}\right)$.
• Black ash is produced when Carbon $\left(\mathrm{C}\right)$ is added to Sodium sulfate $\left({\mathrm{Na}}_2{\mathrm{SO}}_4\right)$ which leads to the conversion of sulfate into sulfide.
• This process is known as Leblanc's process.
• The chemical reactions are depicted below:

$$\begin{gathered} {\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+2\mathrm{C}\left(\mathrm{s}\right)\to {\mathrm{Na}}_2\mathrm{S}\left(\mathrm{aq}\right)+2{\mathrm{CO}}_2\left(\mathrm{g}\right) \\ {\mathrm{Na}}_2\mathrm{S}\left(\mathrm{aq}\right)+{\mathrm{CaCO}}_3\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+\mathrm{CaS}\left(\mathrm{s}\right) \end{gathered}$$