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(a) Give reasons :

(i) Transition metals and their compounds show catalytic activities.

(ii) Separation of a mixture of Lanthanoid elements is difficult.

(iii) Zn,\; Cd and Hg are soft and have low melting point

.(b) Write the preparation of the following :

(i) Na_{2}Cr_{2}O_{7} fromNa_{2}CrO_{4}

(ii) K_{2}MnO_{4} from MnO_{2}

 

 

 
 
 
 
 

Answers (1)

a)

i) Transition metals and their compounds show catalytic activities because of Variable or multiple oxidation states, ability to form complexes, they provide large surface area for adsorption.

ii) Separation of a mixture of Lanthanoid elements is difficult because of Similar size, similar properties

iii) Because they donot have unpaired electron and have weak interatomic metallic bonding also have completely or fully filled d orbitals

b)

i) 2Na2CrO4 + 2 H+ → Na2Cr2O7 + 2 Na+ + H2O

ii) 2MnO2 + 4KOH + O2 → 2K2MnO4 + 2H2O

 

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Safeer PP

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