Question

What happens when a mixture of aluminium powder and powdered manganese(IV) oxide are heated? What type of reaction is it?

Answer 1

• Types of chemical reaction

Combination reaction: Reaction in which two or more reactants combine to form a single product. $\mathrm{A}+\mathrm{B}\to \mathrm{C}$

Decomposition reaction: Reaction in which reactant is broken down into two or more products in the presence of heat, light or electricity. $\mathrm{A}\to \mathrm{B}+\mathrm{C}$.

Displacement reaction: Reaction in which one of the higher reactive element displaces less reactive element from its solution. $\mathrm{A}+\mathrm{BC}\to \mathrm{AC}+\mathrm{B}$ ( Here A is more reactive than B)

Double displacement reaction: Reaction in which ions of both the reactants interchange their place and form new compounds. $\mathrm{AB}+\mathrm{CD}\to \mathrm{AD}+\mathrm{CB}$.

• Reaction:

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

• 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.

• As we can see from activity series aluminium is more reactive than manganese so aluminum can displace manganese from manganese oxide.
• This is a displacement reaction.
• So here displacement of manganese is taking place from ${\mathrm{MnO}}_2$.