If r_(Na^+) and r_(Cl^-) represent the radii of Na^+ and Cl^- ions respectively and n is the number of NaCl units per unit cell, derive an expression for molar volume of the crystal in terms of r_(Na^+), r_(Cl^-) and n.

If r_(Na^+) and r_(Cl^-) represent the radii of Na^+ and Cl^- ions res

1.	If r_(Na^+) and r_(Cl^-) represent the radii of Na^+ and Cl^- ions respectively and n is the number of NaCl units per unit cell, derive an expression for molar volume of the crystal in terms of r_(Na^+), r_(Cl^-) and n.
Answer» Solution :Edge of the unit cell (a)=`2(r_(Na^+)+r_(Cl^-))` VOLUME of the unit cell= `a^3=8(r_(Na^+)+ r_(Cl^-))^3` Volume occupied by 1 mole of NaCl (MOLAR volume ) =`(8(r_(Na^+)+r_(Cl^-))^3)/nxxN_0` where `N_0` = Avogadro's number =`6.023xx10^23`