How many tetrahedral voids are present in 0.4 mole of a compound that forms hcp structure?

How many tetrahedral voids are present in 0.4 mole of a compound that forms hcp structure?
  1. $4.8 \times 10^{23}$
  2. $3.011 \times 10^{23}$
  3. $1.2 \times 10^{23}$
  4. $2.4 \times 10^{23}$

Solution

In HCP structure for each atom one octahedral void and two tetrahedral voids will be present. No. of atoms $=0.4 \times \mathrm{N}_{\mathrm{A}}=0.4 \times 6.022 \times 10^{23}$ No. of tetrahedral voids $=$ No. of atoms $\times 2$ $\begin{aligned} & =0.4 \times 6.022 \times 10^{23} \times 2 \\ & =4.8 \times 10^{23} \end{aligned}$

Asked in: MHT CET 2021 (22 Sep Shift 2)

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