Ifr_(Na^(+)) and r_(Cl^(-))represent the radii ofNa^(+) 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 ofr_(Na^(+)) , t_(Cl^(-)) and n.

Ifr_(Na^(+)) and r_(Cl^(-))represent the radii ofNa^(+) and Cl^(-) ion

1.	Ifr_(Na^(+)) and r_(Cl^(-))represent the radii ofNa^(+) 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 ofr_(Na^(+)) , t_(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)))/N XX N_(0)` where ` N_(0)` = Avogadro's number = ` 6.023 xx 10^(23)`