9.21

[Kelly Kiremidjian 1C]

In #21, where do they get the value of Kb? Also can someone explain this question I'm confused what we are calculating

[Chem_Mod]

Please elaborate on what the question is asking instead of just referring to it.

[Hannah Chew 2A]

Kb is Boltzmann's constant, which is given to us on exams. The question is essentially asking for the entropy based on how many ways can you arrange the molecules. For part a), there is only 1 way to arrange it because they are all the same molecules aligned the same way. Part b), there is 4^64 ways because there are 4 different orientations and 64 molecules. Substitute into S = kblnW.

[torieoishi1A]

a) Entropy of a solid made of 64 molecules in which they are all aligned in the same direction.
First you need to solve for W (orientation^#molecules). therefore, W=1^64=1. Then use the Boltzmann formula: S=klnW. (k=1.381x10^-23J/K #this is a constant that is given). Snce we know ln1=0, S=0.
b) Entropy of a solid made of 64 molecules in which they lie in any one of four orientations with the same energy.
Using the same formula and constant from part a, W=4^64=3.403x10^38. Then S=(1.381x10^-23J/K)ln(3.403x10^38)=1.22x10^-21J/K