Q26 of 35 Page 1

(i) Following is the schematic alignment of magnetic moments:


Identify the type of magnetism. What happens when these substances are heated?


(ii) If the radius of the octahedral void is ‘r’ and radius of the atoms in close packing is ‘R’. What is the relation between ‘r’ and ‘R’?


(iii) Tungsten crystallizes in body centred cubic unit cell. If the edge of the unit cell is 316.5 pm. What is the radius of tungsten atom?

(i)


The type of magnetism shown by the above diagram is Ferrimagnetism. Ferrimagnetism arises due to the unequal number of domains in opposite direction resulting in the some net magnetic moment.


When these substances are heated, they lose the property of ferrimagnetism and become paramagnetic.


(ii) For octahedral void:


r = 0.414 R


(iii) For body-centered cubic unit cell:


r =


As edge length (a) = 316.5 pm


∴ r =


⇒ r = 136.88 pm


Thus, the radius of tungsten atom is 136.88 pm


More from this chapter

All 35 →
24

Answer the following questions

(a) Write the formula of the neutral molecule which is isoelectronic with ClO-.


(b) Draw the shape of H2S2O7.


(c) Nitric acid forms an oxide of nitrogen on reaction with P4.Write the formula of the stable molecule formed when this oxide undergoes dimerisation.


(d) Bleaching action of chlorine is permanent. Justify.

 25

Write the products of the following reactions:

(i)


(ii) 2C6H5CHO + conc. NaOH →


(iii) CH3COOH


(b) Give simple chemical tests to distinguish between the following pairs of compounds:


(i) Benzaldehyde and Benzoic acid


(ii) Propanal and Propanone

 25

(a) Account for the following:

(i) CH3CHO is more reactive than CH3COCH3 towards reaction with HCN.


(ii) 2-Fluorobutanoic acid is a stronger acid than 3-Fluorobutanoic acid.


(b) Write the chemical equations to illustrate the following name reactions:


(i) Etard reaction.


(ii) Rosenmund’s reaction.


(c) Give the mechanism of cyanohydrin formation when carbonyl compounds react with HCN in the presence of alkali.

 26

(i) Identify the type of defect shown in the following figure:


What type of substances show this defect?


(ii) A metal crystallizes in a body centred cubic structure. If ‘a’ is the edge length of its unit cell, ‘r’ is the radius of the sphere. What is the relationship between ‘r’ and ‘a’?


(iii) An element with molar mass 63 g / mol forms a cubic unit cell with edge length of 360.8 pm. If its density is 8.92 g/ cm3. What is the nature of the cubic unit cell?