[Single-digit Integer] X-ray diffraction shows that the unit cell edge length of is 500 pm. If the measured density of is 2.964 g/ml, what per cent of Na+ and Cl- ions must be missing?

Question

[Single-digit Integer] X-ray diffraction shows that the unit cell edge length of $NaCl$ is 500 pm. If the measured density of $NaCl$ is 2.964 g/ml, what per cent of Na+ and Cl- ions must be missing?

Prashant Kotian · Accepted Answer

Correct answer: 5. Theoretical density rho_theo = (Z * M) / (Na * a^3) = (4 * 58.5) / (6 * 10^23 * (5 * 10^-8)^3) = 234 / 75 = 3.12 g/ml. Percentage of missing ions (due to Schottky defects) = (rho_theo - rho_obs) / rho_theo * 100% = (3.12 - 2.964) / 3.12 * 100% = 0.156 / 3.12 * 100% = 5%.

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