Indicate the steps in the preparation of K₂Cr₂O₇from chromite ore.

Solution

The preparation of potassium dichromate from chromite involves the following main steps:
(i) The chromate ore is finely ground and heated strongly with molten alkali in the presence of air.

$\underset{Chromite}{2 {FeCr}_{2} O_{4}} + 8 NaOH + 7 / 2 O_{2} \to \underset{Sodium chromate}{4 {Na}_{2} {Cr}_{2} O_{4}} + {Fe}_{2} O_{3} + 4 H_{2} O$

(ii) The solution of sodium chromate is filtered and acidified with dilute sulphuric acid so that sodium dichromate is obtained.

$\underset{Sodium Chromate}{2 {Fe}_{2} {Cr}_{2} O_{4}} + H_{3} {SO}_{4} \to \underset{Sodium dichromate}{{Na}_{2} {Cr}_{2} O_{7}} + {Na}_{2} {SO}_{4} + H_{2} O$

(iii) A calculated quantity of potassium chloride is added to a hot concentrated solution of sodium dichromate. Potassium dichromate is less soluble therefore it crystallizes out first.

$\underset{Sodium dichromate}{{Na}_{2} {Cr}_{2} O_{7}} + 2 KCl \to \underset{Potassium dichromate}{K_{2} {Cr}_{2} O_{7}} + 2 NaCl$

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

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The D-And-f-Block Elements

Indicate the steps in the preparation of K₂Cr₂O₇from chromite ore.

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

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.

Why do some exceptions to the general electronic configuration of d-block elements exists?

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The D-And-f-Block Elements

Indicate the steps in the preparation of K2Cr2O7 from chromite ore.

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

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.

Why do some exceptions to the general electronic configuration of d-block elements exists?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Indicate the steps in the preparation of K₂Cr₂O₇from chromite ore.

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