Question

1)The vapor pressure of SiCl4 is 100 mm at 4.4 ºC, and a normal boiling point of 57.7 ºC. What is ΔHvap for in k/mol.

2) Copper metal has face-centered cubic unit cell with an edge length of 362 pm. What is the density of the metal in g/cm³?

3)Calculate the vapor pressure of a solution of 1.0 mol of sucrose dissolved in 15.0 mol of water at 25°C. The vapor pressure of water at 25°C = 23.76 mm Hg.

Use the diagram to determine the formula of the compound and coordination number of the Ni. What is the oxidation state (number) of the Ni?

Answer 1

1. ln(P1/P2) = -Hvap/R [1/T1-1/T2]

ln (760/100) = -Hvap/R (1/330.7 -1/277.4)

2.028 = -Hvap/8.314 J/K/mol *(- 5.8 *10^-4)

Hvap = 2.91 *10^4 J/ mol

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2) Density (d) = M*Z/a^3 *N

where M = molar massof copper= 63.5 gm/mol

number of atoms = 4 (for FCC

a = edge length = 362 pm = 362 * 10^-10 m , N = avogadro number = 6.023*10^23

d = 63.5 gmmol^-1 *4/( 362 * 10^-10 m)^3*6.023*10^23

= 8.9gm/cc

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total moles = 1+15 = 16

mole fraction of water = 15/16 =0.94

Psoln = mole fraction of water * vap pressure of water = 0.94 * 23.76 mm Hg =22.28 mm Hg

Vapour pressure of the solution is 22.28 mm Hg