Describe the preparation of potassium permanganate. How does the acidified permanganate solution reacts with (a) iron (II) ions (b) SO₂ and (c) oxalic acid ? Write the ionic equations for the reactions.

Solution

Preparation of KMnO₄ from pyrolusite ore (MnO₂) involves the following steps:
(i) Fusion of ore with alkali in presence of air : Pyrolusite ore is fused with alkali in the presence of air when potassium manganate is obtained as green mass.
2MnO₂ + 4KOH + O₂  → 2K₂MnO₄ + 2H₂O
(green mass)
The green mass is dissolved in water to obtain aqueous solution of potassium manganate. The insoluble impurities of sand and other metal oxides are removed by filtration.
(ii) Oxidation of manganate into permanganate : The aqueous solution of K₂MnO₄ is oxidised electrolytically or by using ozone or Cl₂ to obtain potassium permanganate. The process is carried out till green colour disappear and solution acquires distinct pink colour. ${MnO}_{4}^{2 -} \to {MnO}_{4}^{-} + e^{-} (Oxidation at anode) H_{2} O + e^{-} \to 1 / 2 H_{2} + (OH)^{-} (Reduction at cathode) The overall reaction 2 K_{2} {MnO}_{4} + {Cl}_{2} \to 2 {KMnO}_{4} + 2 KCl g r e e n p i n k c o l o u r^{{^{}}^{}^{}^{}^{}^{}^{}^{}^{}^{}^{}}$
Potassium permanganate is crystallised out from the solution.
Oxidising Properties: It acts as a powerful oxidising agent in different media differently. In acidic medium, it oxidises iron(II) salts to iron(III) salts,
SO₂ to H₂SO₄ and oxalic acid to CO₂ and H₂O.
(a)    It oxidises iron(II) salt to iron(III) salts.
2MnO₄^2–+ 16H⁺+ 10Fe²⁺ → 2Mn²⁺ + 8H₂O + 10Fe³⁺(b)    It oxidised sulphur dioxide to sulphuric acid.
2MnO₄^– + 5SO₂ + 2H₂O → 5SO₄^2–+ 2Mn²⁺ 4H⁺(c)    It oxidises oxalic acid to CO₂ and H₂O
2MnO₄^– + 16H⁺ + 5C₂O₄² → 2Mn²⁺ + 8H₂O + 10CO₂

Some More Questions From The d-And-f-Block Elements Chapter

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The D-And-f-Block Elements

Describe the preparation of potassium permanganate. How does the acidified permanganate solution reacts with (a) iron (II) ions (b) SO₂ and (c) oxalic acid ? Write the ionic equations for the reactions.

Some More Questions From The d-And-f-Block Elements Chapter

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Which is a stronger reducing agent Cr²⁺ or Fe²⁺ and why?

Explain why Cu⁺ ion is not stable in aqueous solutions?

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

The outer electronic configuration of copper is 3d¹⁰ 4s¹, yet it is considered transition element. Why?

Why the melting points of transition elements are high?

Why Zn, Cd and Hg are not regarded as transition elements?

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The D-And-f-Block Elements

Describe the preparation of potassium permanganate. How does the acidified permanganate solution reacts with (a) iron (II) ions (b) SO2 and (c) oxalic acid ? Write the ionic equations for the reactions.

Some More Questions From The d-And-f-Block Elements Chapter

How would you account for the irregular variation of ionisation enthalpies (first and second) in the first series of the transition elements?

Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?

Which is a stronger reducing agent Cr2+ or Fe2+ and why?

Explain why Cu+ ion is not stable in aqueous solutions?

Actinoid contraction is greater from element to element than lanthanoid contraction. Why?

On what ground can you say that scandium (Z = 21) is a transition element but zinc (Z = 30) is not?

The outer electronic configuration of copper is 3d10 4s1, yet it is considered transition element. Why?

Why the melting points of transition elements are high?

Why Zn, Cd and Hg are not regarded as transition elements?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Describe the preparation of potassium permanganate. How does the acidified permanganate solution reacts with (a) iron (II) ions (b) SO₂ and (c) oxalic acid ? Write the ionic equations for the reactions.

Which is a stronger reducing agent Cr²⁺ or Fe²⁺ and why?

Explain why Cu⁺ ion is not stable in aqueous solutions?

The outer electronic configuration of copper is 3d¹⁰ 4s¹, yet it is considered transition element. Why?