Consider the four-atom ammonia molecule illustrated in Figure 20.14.

(a) Which of the three rotational degrees of freedom can store thermal energy?

(b) Based on your answer to part \(a\), what is the thermal energy per molecule? 

(c) What is the heat capacity per molecule? 

(d) Does your prediction in part \(c\) agree with the experimental value listed in Table 20.3?

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Table 20.3 Heat capacities per particle in units of ky Class Material Cy/kB Monatomic gases helium 1.50 argon 1.50 krypton 1.50 xenon 1.51 radon 1.51 Polyatomic gases ammonia 3.37 hydrogen 2.47 nitrogen 2.50 Liquids mercury 3.38 water 8.97 Solids aluminum 2.91 copper 2.94 gold 3.08 iron 3.02 silver titanium zinc 3.05 3.04 3.05 All values are reported at a temperature of 298 K and atmospheric pres- sure and with gases held at constant volume (as indicated by the subscript V on Cy).