The number of unit cells in 8 gm of an element X (atomic mass 40) which crystallizes in bcc pattern is ($N_A$ is the Avogadro number) (a) $6.023 \times 10^{23}$ (b) $6.023 \times 10^{22}$ (c) $60.23 \times 10^{23}$ (d) $\dfrac{6.023 \times 10^{23}}{8 \times 40}$

The number of unit cells in 8 gm of an element X (atomic mass 40) which crystallizes in bcc pattern is (NA is

Choose the Best Answer · Q7

N_A

(a)

6.023 \times 10^{23}

(b)

6.023 \times 10^{22}

(c)

60.23 \times 10^{23}

(d)

\dfrac{6.023 \times 10^{23}}{8 \times 40}

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Step 1. Moles of X in 8 g $= \dfrac{8\ \text{g}}{40\ \text{g mol}^{-1}} = 0.2$ mol.

Step 2. Number of atoms $= 0.2 \times N_A = 0.2 \times 6.023\times10^{23} = 1.2046\times10^{23}$ atoms. …