using X-ray diffraction method , the unit length of NaCl crystal was observed to be 0.5627nm. The density of the crystal was found to be 2.164gcm-3 what type of defect exist in the crystal ? calculate the percentage Na+ and Cl- missing from missing from the crystal lattice 

Dear Student,

NaCl has an ionic structure. So, the crystal can have only ionic defects.

We know that NaCl has fcc structure.
So , z = 4, M = 58.5 g mol-1,a = 0.5627 nm=5.627 x 10-8 cm , NA = 6.022 x 1023
Density = d = ZMa3NA=4 × 58.55.627×10-83×6.022 ×1023=2.18 g cm-3
But, observed density= 2.164 < d
Since the stoichiometry of the compound is maintained but the observed density is lesser than the calculated density, it has a Schottky type defect.

Now, change in density = 2.18-2.164 = 0.016 g cm-3
So , 
Percentage of ions missing = Percentage of change in mass = 0.0162.18×100=0.734%

Hope this information will clear your doubts about this topic.

If you have any doubts just ask here on the ask and answer forum and our experts will try to help you out as soon as possible.

Also CLICK HERE and check out the POWER TIPS for JEE Advanced 2017.


  • 0
What are you looking for?