Potassium chloride crystallises in the NaCl type lattice with edge $630 pm$ (molar mass $74.5 g mo l^{- 1}$ ). Use $N_{A} = 6.022 \times 1 0^{23} mo l^{- 1}$ . Calculate its density in $g c m^{- 3}$ (two decimals).

Numerical answer type, answer in g/cm^3, tolerance 0.02.

Answer: 1.98 g/cm^3

Z = 4

for the NaCl structure.

ρ = \frac{4 \times 74.5}{6.022 \times 1 0 ^{23} \times ( 6.30 \times 1 0 ^{- 8} ) ^{3}} = 1.98 g c m^{- 3}