Assume a heteronuclear diatomic molecule,AB,forms a one-dimensional crystal by lining up along the x-axis.Also assume that each molecule can only have one of six possible orientations,corresponding to atom A facing in either the positive or negative direction along the x-,y-,or z-axis.If the molecules are arranged randomly in the six directions,the molar entropy at absolute zero should be

Question

Quizplus · Accepted Answer

For a one-dimensional crystal, the only contribution to entropy comes from the possible orientations of the molecules. Since each molecule can have one of six possible orientations, the entropy is given by S = k ln 6, where k is Boltzmann's constant. At absolute zero, all molecules will be in their lowest energy state, so the entropy will be zero. Thus, the molar entropy at absolute zero is S = 0 for all temperatures below the melting point of the crystal. Therefore, the correct answer is choice A.

Assume a Heteronuclear Diatomic Molecule,AB,forms a One-Dimensional Crystal by Lining