Number of unit cells in 0.97g of zns (sphalerite) is
A. 0.25NA
B. 0.025NA
C. 2.5*10^-3 NA
D. 2.5*10^-4 NA
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Number of unit cells in 0.97g of zns (sphalerite) is
A. 0.25NA
B. 0.025NA
C. 2.5*10^-3 NA
D. 2.5*10^-4 NA
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We have to find the number of unit cells in 0.97 g of ZnS (sphalerite).
solution : molecular weight of ZnS = 97 g/mol ( approximately)
given weight of ZnS = 0.97 g
so no of moles of ZnS = given weight/molecular weight
= 0.97/97
= 0.01
now no of molecules in 0.01 moles of ZnS = 0.01 × Avogadro's number
= 0.01 NA
as structure of ZnS is face centered cubic lattice.
so, number of molecules per unit cell is 4
now number of unit cell in 0.01 NA molecules = 0.01 NA/4
= 0.25 × 10¯² NA
= 2.5 × 10¯³ NA
Therefore the number of unit cells in 0.97 g of ZnS is 2.5 × 10¯³ NA