Write steps involved in the preparation of (i) Na₂CrO₄ from chromite ore and (ii) K₂MnO₄ from pyrolusite ore.

Solution

(i) Na₂CrO₄ from chromite ore: Preparation of sodium chromate : The chromite ore (FeO.Cr₂O₃) is finely powdered and mixed with sodium carbonate and quick lime and then heated to redness in a reverberatory furnace with free supply of air.
4FeO.Cr₂O₃ + O₂ -->2Fe₂O₃ +4Cr₂O₃
[4Na₂CO₃ +2Cr₂O₃ +3O₂--->4Na₂CrO₄ +4Cr2O3]x2
4FeO.Cr₂O₃ +8Na₂CO₃ +7O₂--->8Na₂CrO₄ +2Fe₂O₃ +8CO₂

The mass is then extracted with water, when sodium chromate is completely dissolved while Fe₂O₃ is left behind.

(ii) K₂MnO₄ from pyrolusite ore:
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.

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.

2 {MnO}_{2} + 4 KOH + O_{2} \to \underset{(green mass)}{2 K_{2} {MnO}_{4}} + 2 H_{2} O

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

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The D-And-f-Block Elements

Write steps involved in the preparation of (i) Na₂CrO₄ from chromite ore and (ii) K₂MnO₄ from pyrolusite ore.

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

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?

Name the first element of 3rd transition series.

Though copper, silver and gold have completely filled sets of d-orbitals yet they are considered as transition metals. Why?

Why are transition elements so named?

Why are transition elements known as d-block elements?

Write the general electronic configuration of d-block elements.

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The D-And-f-Block Elements

Write steps involved in the preparation of (i) Na2CrO4 from chromite ore and (ii) K2MnO4 from pyrolusite ore.

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

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?

Name the first element of 3rd transition series.

Though copper, silver and gold have completely filled sets of d-orbitals yet they are considered as transition metals. Why?

Why are transition elements so named?

Why are transition elements known as d-block elements?

Write the general electronic configuration of d-block elements.

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Write steps involved in the preparation of (i) Na₂CrO₄ from chromite ore and (ii) K₂MnO₄ from pyrolusite ore.

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