Problem 1 Calcium metal has a density of 1.55 g/cm3 and crystallizes in a cubic

Question

Problem 1 Calcium metal has a density of 1.55 g/cm3 and crystallizes in a cubic unit cell with an edge length of 558.2 pm A) How many Ca atoms are in one unit cell? B) In which of the three cubic unit cells does calcium crystallize? Problem 2 Oxygen has Tt=54.3K, Pt=1.14 mm Hg, Tc= 154.6 K, and Pc= 49.77 atm. The density of the liquid is 1.14 g/cm3, and the density of the solid is 1.33 g/cm3. Sketch a phase diagram for oxygen, and label all points of interest. I apologize but these two questions are bumming me out.

Explanation / Answer

1) density = 1.55= (z x M)/(a^3 xN) z= no of Ca atoms per unit cell , M= mol mass of Ca = 40.078 N= avagadro number = 6.023 x10^ 23 , a = 558.2 pm 1.55 = z x 40.078/(558.2 x10^ -10)^3 x 6.023 x10^ 23 z = 4 B) hence Ca crystalises in FCC lattice i.e face centered cubic lattice

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