Question

Aluminium metal displaces manganese from manganese ($\mathrm{IV}$) oxide giving manganese and aluminium oxide. Which is more reactive: manganese or aluminium?

Answer 1

1. Chemical reaction:

$4\mathrm{Al}\left(\mathrm{s}\right)+3{\mathrm{MnO}}_2\left(\mathrm{s}\right)\to 2{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3\mathrm{Mn}\left(\mathrm{s}\right)$
Aluminium Manganese($\mathrm{IV}$) oxide Aluminum oxide Manganese

2. Activity series of metals
Elements are arranged on the basis of decreasing order of reactivity.
$\mathrm{K}>\mathrm{Na}>\mathrm{Ca}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Mn}>\mathrm{Zn}>\mathrm{Fe}>\mathrm{Ni}>\mathrm{Sn}>\mathrm{Pb}>\mathrm{H}>\mathrm{Cu}>\mathrm{Hg}>\mathrm{Ag}>\mathrm{Au}>\mathrm{Pt}$
Here potassium is highly reactive metal and platinum is least reactive metal.

3. Since aluminium is more reactive than manganese, aluminium can displace manganese.

4. Here aluminium is more reactive.