Question

Solve this:
Q.(a). Arrange the following in increasing order of Acidic character.
$Mn{O}_2,M{n}_2{O}_7,MnO$.
(b) What happens when $KMn{O}_4$ is heated ? Give chemical equation.
(c) What are non-stoichiometric oxides ? Give one example.

Answer 1

Dear Student,

$$\begin{gathered} \left(\mathrm{a}\right)\mathrm{Acidic}\mathrm{character}\mathrm{increases}\mathrm{with}\mathrm{the}\mathrm{increase}\mathrm{in}\mathrm{oxidation}\mathrm{state}\mathrm{of}\mathrm{the}\mathrm{central}\mathrm{metal}\mathrm{atom}. \\ \mathrm{Oxidation}\mathrm{state}\mathrm{of}\mathrm{Mn}\mathrm{in}{\mathrm{MnO}}_2\mathrm{is}+4,\mathrm{in}{\mathrm{Mn}}_2{\mathrm{O}}_7\mathrm{is}+7\mathrm{and}\mathrm{in}\mathrm{MnO}\mathrm{is}+2 \\ \mathrm{So},\mathrm{the}\mathrm{order}\mathrm{will}\mathrm{be}\mathrm{MnO}<{\mathrm{MnO}}_2<{\mathrm{Mn}}_2{\mathrm{O}}_7 \\ \left(\mathrm{b}\right)\mathrm{Potassium}\mathrm{permanganate}\mathrm{on}\mathrm{heating}\mathrm{decomposes}\mathrm{to}\mathrm{give}\mathrm{potassium}\mathrm{mangante}. \\ 2{\mathrm{KMnO}}_4\to {\mathrm{K}}_2{\mathrm{MnO}}_4+\hspace{0.17em}{\mathrm{MnO}}_2+\hspace{0.17em}{\mathrm{O}}_2 \\ \left(\mathrm{c}\right)\mathrm{The}\mathrm{oxides}\mathrm{in}\mathrm{which}\mathrm{metal}\mathrm{to}\mathrm{oxygen}\mathrm{ratio}\mathrm{is}\mathrm{not}\mathrm{whole}\mathrm{number}\mathrm{are}\mathrm{called}\mathrm{non}-\mathrm{stoichiometric}\mathrm{oxides}. \\ \mathrm{For}\mathrm{eg}.{\mathrm{Fe}}_{0.94}\mathrm{O} \end{gathered}$$