An element X (Atomic weight = 80 g/mol) has a face-centered cubic structure. Calculate the number of unit cells in 8 g of X:
Correct answer: D. 0.025 x NA
- A. 0.4 x NA
- B. 0.1 x NA
- C. 4 x NA
- D. 0.025 x NA
Explanation
First, find the moles of X: 8 g / 80 g/mol = 0.1 mol. Find the number of atoms: 0.1 × Nₐ. An FCC unit cell contains 4 atoms. Therefore, the number of unit cells is (0.1 × Nₐ atoms) / (4 atoms/cell) = 0.025 × Nₐ.
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