Number of moles of metal in close packed structure \(=0.5 \mathrm{~mol}\)
No. of atoms in 1 mole of mole \(=N_A\)
\(\therefore\) Number of atoms in \(0.5 \mathrm{~mol}\) of metal
\(=0.5 \times 6.022 \times 10^{23}=3.011 \times 10^{23}\)
Also, number of tetrahedral voids \(=2 \times\) number of metal atoms in close packed structure
\(\therefore\) Number of tetrahadral voids \(=2 \times 3.011 \times 10^{23}\)
\(=6.022 \times 10^{23} \approx 1 \mathrm{~mol}\)
Number of octahedral void \(=\) number of metal atoms in close packed structure
So, that number of octahedral voids \(=3.011 \times 10^{23}\)
\(=0.5 \mathrm{~mol}\)
Total number of voids
\(\begin{aligned}
& =\text { tetrahedral void }+ \text { octahedral void } \\
& =6.022 \times 10^{23}+3.011 \times 10^{23} \\
& =9.05 \times 10^{23} \approx 1.5 \mathrm{~mol}
\end{aligned}\)
Therefore, total number of voids and tetrahedral voids in hexagonal close packed structure are \(1.5 \mathrm{~mol}\) and \(1.0 \mathrm{~mol}\) respectively. Hence, option (a) is the correct answer.