Question

An element crystallises in bcc structure. The number of unit cells of an element in 4 g of it is (given atomic mass = 40).

• A. \( \dfrac{0.1 \times N_A}{2} \)
• B. \( 2 \times 0.1 N_A \)
• C. \( 0.1 N_A \)
• D. \( 2 \times N_A \)

Hint:

Remember: bcc unit cell contains 2 atoms, fcc contains 4, and simple cubic contains 1 atom.

Answer 1

The Correct Option is A

Step 1: Calculating number of moles.
\[ \text{Number of moles} = \frac{4}{40} = 0.1 \]

Step 2: Calculating number of atoms.
\[ \text{Number of atoms} = 0.1 \times N_A \]

Step 3: Using bcc structure information.
In a body-centered cubic (bcc) structure, each unit cell contains 2 atoms.

Step 4: Calculating number of unit cells.
\[ \text{Number of unit cells} = \frac{0.1 \times N_A}{2} \]

Step 5: Conclusion.
Hence, the correct answer is option (A).