Chemistry 12 Chapter 8 Exemplar Solutions the P and F Block Elements Part 8

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VI. Long Answer Type

Question 64:

Identify A to E and also explain the reactions involved.

Reactions involved

Reactions Involved


Question 65:

When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with , orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.


Question 66:

When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.


Question 67:

On the basis of Lanthanoid contraction, explain the following:

(i) Nature of bonding in and .

(ii) Trends in the stability of salts of lanthanoids from to .

(iii) Stability of the complexes of lanthanoids.

(iv) Radii of and block elements.

(v) Trends in acidic character of lanthanoid oxides.



(i) As the size decreases covalent character increases. Therefore is more ionic and is more covalent.

(ii) As the size decreases from to , stability of oxosalts also decreases.

(iii) Stability of complexes increases as the size of lanthanoids decreases.

(iv) Radii of and block elements will be almost same.

(v) Acidic character of oxides increases from to .

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