Chemistry > d and f Block Elements > 5.0 Potassium permanganate
d and f Block Elements
1.0 General Introduction and Electronic Configuration
2.0 Occurrence and General Characteristics of Transition Elements
3.0 General Trends in properties of First Row Elements
3.1 Ionisation Enthalpy
3.2 Oxidation State
3.3 Atomic and Ionic Radii
3.4 Colour
3.5 Catalytic properties
3.6 Magnetic Properties
3.7 Formation of Interstitial Compounds
3.8 Alloy Formation
4.0 Potassium dichromate
5.0 Potassium permanganate
5.1 Properties of potassium permanganate
5.2 Structure of manganate ion and permanganate ion
5.3 Disproportion of an oxidation state
5.4 Uses
6.0 F-Block Elements - Introduction
7.0 Lanthanoid Series
7.1 Position of Lanthanoid Series
7.2 Electronic configuration of lanthanoids
7.3 Oxidation States
7.4 Chemical Reactivity of Lanthanides
8.0 Lanthanoid Contraction and its consequence
9.0 Actinoids Series
9.1 Position of Actinoids in periodic table
9.2 Electronic Configuration of actinoids
9.3 Oxidation states of actinoids
10.0 Comparison between lanthanoids and actinoids
5.1 Properties of potassium permanganate
3.2 Oxidation State
3.3 Atomic and Ionic Radii
3.4 Colour
3.5 Catalytic properties
3.6 Magnetic Properties
3.7 Formation of Interstitial Compounds
3.8 Alloy Formation
5.2 Structure of manganate ion and permanganate ion
5.3 Disproportion of an oxidation state
5.4 Uses
7.2 Electronic configuration of lanthanoids
7.3 Oxidation States
7.4 Chemical Reactivity of Lanthanides
9.2 Electronic Configuration of actinoids
9.3 Oxidation states of actinoids
1. It is deep purple crystalline solid and moderately soluble in water and melting point is $523\ K$.
2. Action of heat:
- On heating it is converted to potassium permanganate with evolution of ${O_2}$. \[2KMn{O_4}\xrightarrow{\Delta }{K_2}Mn{O_4} + Mn{O_2} + {O_2}\]
- ${K_2}Mn{O_4}$ on heating at red hot decomposes to ${K_2}Mn{O_3}$ \[2{K_2}Mn{O_4}\xrightarrow{{\operatorname{Re} d{\text{ }}Hot}}2{K_2}Mn{O_3} + {O_2} \uparrow \]
3. Action of ${H_2}S{O_4}$:
- $KMn{O_4}$ on reacting with cold ${H_2}S{O_4}$ form $M{n_2}{O_7}$ which on warming produces $Mn{O_2}$. $$2KMn{O_4} + 2{H_2}S{O_4} \to M{n_2}{O_7} + 2KHS{O_4} + {H_2}O$$ $$2M{n_2}{O_7} \to 4Mn{O_2} + 3{O_2}$$
- $KMn{O_4}$ on reacting with warm conc. ${H_2}S{O_4}$ produces ${O_2}$. $$4KMn{O_4} + 6{H_2}S{O_4} \to 2{K_2}S{O_4} + 2MnS{O_4} + 6{H_2}O + 5{O_2}$$
4. Action of ${H_2}$:
$KMn{O_4}$ on reacting with ${H_2}$ gas produce $KOH$. $$2KMn{O_4} + 5{H_2} \to 2KOH + 2MnO + 4{H_2}O$$
5. Oxidising property: $KMn{O_4}$ acts as a powerful oxidizing agent in neutral acid and alkaline medium.
- In neutral Medium: In neutral medium $KMn{O_4}$ oxidize $MnS{O_4}$ to $Mn{O_2}$, manganese dioxide. $$2KMn{O_4} + 3MnS{O_4} + 2{H_2}O \to 5Mn{O_2} + {K_2}S{O_4} + 2{H_2}S{O_4}$$$$2KMn{O_4} + {H_2}O \to 2KOH + 2Mn{O_2} + 3[O]$$
- In alkaline medium:
(a) It is reduced to potassium manganate and then to manganese dioxide. $$2KMn{O_4} + 2KOH \to 2KMn{O_4} + {H_2}O + [O]$$$$2{K_2}Mn{O_4} + 2{H_2}O \to 2Mn{O_2} + 4KOH + 2[O]$$ Example. $$2KMn{O_4} + {H_2}O + KI \to 2Mn{O_2} + 2KOH + KI{O_3}$$$$C{H_2} = C{H_2} + {H_2}O + [O] \to C{H_2}OH - C{H_2}OH$$
(b) Bayer's Test: Alkaline $KMn{O_4}$ on reacting with alkanes decolourise purple colour of solution and form glycols which is the test for unsaturation.
- Acidic medium: $KMn{O_4}$ acts as oxidising agent in presence of ${H_2}S{O_4}$. $$2KMn{O_4} + 3{H_2}S{O_4} \to {K_2}S{O_4} + MnS{O_4} + 3{H_2}O + 5[O]$$ Example:
i) Oxidation of oxalic acid into $C{O_2}$: $$2Mn{O_4}^ - + 5{H_2}{C_2}{O_4} + 6{H^ + } \to 2M{n^{ + 2}} + 10C{O_2} + 8{H_2}O$$
ii) Oxidation of FAS: $$Mn{O_4}^ - + 5F{e^{ + 2}} + 8{H^ + } \to 5F{e^{ + 3}} + M{n^{ + 2}} + 4{H_2}O$$
iii) Oxidation of ${H_2}{O_2}$: $$2Mn{O_4}^ - + 6{H^ + } + 5{H_2}{O_2} \to 2M{n^ + } + 8{H_2}O + 5{O_2}$$
iv) Following are the examples of oxidation reaction of acidic $KMn{O_4}$.
- Oxidation of ${H_2}S$ to sulphur: $${H_2}S + (O) \to {H_2}O + S$$
- Oxidation of $S{O_2}$ to ${H_2}S{O_4}$: $$S{O_2} + (O) + {H_2}O \to {H_2}S{O_4}$$
- Oxidation of nitrites to nitrate: $$KN{O_2} + (O) \to KN{O_3}$$
- Oxidation of Sulphites to Sulphates: $$N{a_2}S{O_3} + (O) \to N{a_2}S{O_4}$$
- Oxidation of halides to halogens: $$2KI + 2{H_2}S{O_4} + (O) \to {K_2}S{O_4} + {H_2}O + I$$
