Question

Consider a disordered crystal of phosgene in which each trigonal planar COCl2 molecule is oriented randomly in one of three possible ways. Use Boltzmann's equation to calculate the entropy of the disordered state of the crystal if the crystal contains A.900 molecules B. 9 mol

Answer 1

A.

S = n.k.ln(W)

where S is entropy, n is no. of molecules, k is Boltzmann constant, W is no. of possible ways a molecule is oriented

S = 900 1.38 10^-23 ln (3)

S = 1.36 10^-20 J/K

B.

1 mol = 6.023 10²³ molecules

9 moles = 9 6.023 10²³ = 5.42 10²⁴ molecules

S = 5.42 10²⁴ 1.38 10^-23 ln (3)

S = 82.17 J/K