CuI, CsI, and NaI each adopt a different type of structure. The three different structures are those shown in Figure 12.26.
(a) Use ionic radii, \(\operatorname{Cs}^{+}(r=1.81 \AA)\), \(\mathrm{Na}^{+}(r=1.16 \AA), \mathrm{Cu}^{+}(r=0.74 \AA)\), and, \(\mathrm{I}^{-}(r=2.06 \AA)\), to predict which compound will crystallize with which structure.
(b) What is the coordination number of iodide in each of these structures?
Text Transcription:
Cs^+(r=1.81 \AA)
Na^+(r=1.16 \AA), Cu^+(r=0.74 \AA)
I^-(r=2.06 \AA)
Chapter 20 Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions Key Principles to focus on while studying this chapter • A process such as a rock falling or a fuel burning is said to be spontaneous because, once started, it continues by itself. Neither the first law of thermodynamics (law of conservation of energy) nor the sign of DH can predict which processes are spontaneous, but any reaction proceeds spontaneously toward equilibrium. (Section 20.1) • The total kinetic energy of a system consists of all the motions of its particles— rotations, vibrations, and translations—each of which is quantized. A microstate of the system is any specific combination of these quantized energy states. The entropy (S ) of a system is directly related to the number of microstates (W ) into which the system disperses its energy, which is closely associated with the freedom of motion of the particles. (Section 20.1) • A substance has more entropy in its gaseous than its liquid state and more in its liquid than its solid state. (Section 20.1) • The second law of thermodynamics states that a spontaneous process occurs in the direction that increases the entropy of the universe (system plus surroundings). In other words, a change occurs spontaneously if the energy of the universe becomes more dispersed. (Section 20.1) • The third law of thermodynamics—the entropy of a perfect crystal is zero at 0 K—allows us to calculate absolute entropies. The standard molar entropy (S 8) of a substance is influenced by temperature, physical state, dissolution, and atomi
