Question

State one chemical test between each of the following pairs:

Manganese dioxide and copper (II) oxide

Answer 1

With Hydrochloric acid:

1. Upon heating Manganese Dioxide (${\mathrm{MgO}}_2$) with concentrated Hydrochloric acid ($\mathrm{HCl}$), a greenish-yellow gas is evolved. This gas is Chlorine.

${\mathrm{MnO}}_2\left(g\right)+4\mathrm{HCl}\left(aq\right)\stackrel{\Delta }{⟶}{\mathrm{MnCl}}_2\left(aq\right)+2{\mathrm{H}}_2\mathrm{O}\left(l\right)+{\mathrm{Cl}}_2\left(g\right)$

2. Upon heating Copper (II) Oxide ($\mathrm{CuO}$) with concentrated Hydrochloric acid $\mathrm{HCl}$, no gas is evolved.

$\mathrm{CuO}\left(s\right)+2\mathrm{HCl}\left(aq\right)\stackrel{\Delta }{⟶}{\mathrm{CuCl}}_2\left(aq\right)+{\mathrm{H}}_2\mathrm{O}\left(l\right)$

Hence, Hydrochloric acid ($\mathrm{HCl}$) can be used to distinguish between Manganese Dioxide and Copper (II) Oxide.