Calculate the value of Avogadro's number from the following data : Density of NaCl = 2.165 g cm^(-3), Distance betweenNa^(+) and Cl^(-)in NaCl = 281 pm.

Calculate the value of Avogadro's number from the following data : Den

1.	Calculate the value of Avogadro's number from the following data : Density of NaCl = 2.165 g cm^(-3), Distance betweenNa^(+) and Cl^(-)in NaCl = 281 pm.
Answer» Solution :A unit cell of NaCl contains 4 NaCl units, therefore, Z = 4 M = 23 + 35.5 = 58.5g ` "MOL"^(-1)` , p = 2.165 g` cm^(-3)` As distance between ` Na^(+) and Cl= 281` pm` therefore ` Edge of the unit cell ` = 2 xx 281 = 562 ` pm ( Edge is the distance from ` Na^(+) "to" Na^(+) "ION or " Cl^(-) "to" Cl^(-)` .see Fig .1.33 g , page 1/26) substituting these values in the EXPRESSION , ` p = ( Z xx M)/ (a^(3) xx N_(0)) ` `2.165 "gcm" ^(-3)= ( 4 xx 58.5"g mol"-1)/( 562 xx 10^(-10)"cm") ^(3) xx N_(0) or N_(0) = 6.09 xx 10^(23)mol ^(-1)`