Q11 of 31 Page 1

An element crystallizes in a f.c.c. lattice with cell edge of 400 pm. The density of the element is How many atoms are present in 280 g of the element?

Given: Z(no of unit cells) = 4 (f.c.c)


Edge length (a) = 400pm = 4 × 10-8 cm


Density (ρ) = 7 g/cm


NA = 6.022 × 1023 atoms


Now we apply the formula,



We can also write,



⇒


⇒ M= 67.2 g/mol


Now, if 67.2 g/mol = 6.022 × 1023 atoms



⇒ 25.11 × 1023 atoms


Thus, 25.11 × 1023 atoms are present in 300 g of the element


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