Thallium(I) bromide (M = 284.3) adopts the cubic unit cell shown below, with an

Question

Thallium(I) bromide (M = 284.3) adopts the cubic unit cell shown below, with an edge length a = 397 pm. What is the density of TlBr? 5.42 g cm^-3 7.55 g cm^-3 18.0 g cm^-3 22.4 g cm^-3 Which of the following properties is not typical of metallic solids? High vapor pressure High coordination number of atoms in the lattice High electrical conductivity High thermal conductivity Given O(g) + e^- (g) rightarrow O^- (g) telta H^degree = + 142 kJ mol^-1 O(g) + 2e^- (g) rightarrow O^2- (g) telta H^degree = + 702 kJ mol^-1

Explanation / Answer

(17) From unit cell provided,

at 8 corners 8 Br- ions are there, which can contribute 1/8 part each so in atoal 8 * (1/8) = 1 ion per unit cell.

and Tl is there at centre of unit cell which completely beongs to one unitcell.

So, number of formula units per unit cell = 1

density = Z M / NA a 3

d = 1 * 284.3 / (6.022 * 1023 (397 * 10-12)3)

d = 7.55 * 106 g/m3

d = 7.55 * 106 * 10-6 g/cm3

d = 7.55 g/cm3

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