A crystal of lead (II) sulphide has NaCl strcuture . In this crystal the shorest distance between a `Pb^(2+)` ion and `S^(2-)` ion is 297 pm . What is the volume the of unit cell in lead sulphide ?

Explanation

NaCl type FCC
`r_(+)+r_(-)=(a)/(2)=297`
`implies a=297xx2=594` pm
`=594xx10^(-10)` cm
`=5.94xx10^(-8)` cm
`a^(3)=volume %=2.096 xx10^(-22) cm^(3)`