No. of octahedral voids in 1 mol=No. of Effective atoms=6
& No. of tetrahedral voids in 1 mol=2*No. of Effective atoms=12
=> Total voids in 1 mol of HCP =6 +2*6=6+12=18
=> Total voids in 0.5 mol of HCP=9
NCERT: Intext question
A compound forms hcp structure. What is the total number of voids in 0.5 mol of it? How many of these are tetrahedral voids?
No. of octahedral voids in 1 mol=No. of Effective atoms=6
& No. of tetrahedral voids in 1 mol=2*No. of Effective atoms=12
=> Total voids in 1 mol of HCP =6 +2*6=6+12=18
=> Total voids in 0.5 mol of HCP=9