KCl crystallizes in the same type of lattice as does NACl. Given that rNa+rCl−=0.55 and rK+rCl−=0.74. Calculate the ratio of the side of the unit cell for KCl to that of NaCl.
1.123
→ NaCl cyrstallises in fcc.
⇒rNa+Cl−=a2
Given, rNa+rCl−=0.55; Adding 1 to both sides
rNa++rCl−rCl−=1.55……(1)
Now, rK+rCl−=0.74; Adding 1 to both sides
rK++rCl−rCl−=1.74……(2)
21⇒rK++rCl−rNa++rCl−=1.741.55⇒aKClaNaCl=1.741.55=1.123