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JEE Advanced 2025 · Paper 2, Chemistry question 9

The density (in g cm−3\mathrm{g\,cm^{-3}}) of the metal which forms a cubic close packed (ccp) lattice with an axial distance (edge length) equal to 400 pm is _____.

Use: Atomic mass of metal =105.6= 105.6 amu and Avogadro's constant =6×1023 mol−1= 6\times10^{23}\ \mathrm{mol^{-1}}

Answer and worked solution

Official answer: 10.85

A ccp (fcc) cell has Z=4Z=4 atoms and edge a=400a=400 pm =4×10−8=4\times10^{-8} cm.
ρ=ZMNAa3=4×105.66×1023×64×10−24=422.438.4=11.0 g cm−3.\rho=\frac{ZM}{N_Aa^3}=\frac{4\times105.6}{6\times10^{23}\times64\times10^{-24}}=\frac{422.4}{38.4}=11.0\ \text{g cm}^{-3}.