Q12 of 27 Page 1

Answer the following:

(a) What is the formula of a compound in which element Y forms ccp lattice and atoms X occupy 1/3rd of tetrahedral voids?


(b) What type of non-stoichiometric point defect leads to colour in alkali metal halides?


(a) Since, Y forms ccp lattice, the no. of atoms of Y =


= 4


No. of tetrahedral voids in lattice = 2 (no. of atoms of Y)


= 2


Since, X occupy 1/3rd of tetrahedral voids, then no. of atoms of X = 8 =


Formula of compound =


= X2Y3


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