Hydrogen molar heat capacities

The explanation of the hydrogen atom spectmm and the photoelectric effect, together with other anomalous observations such as the behaviour of the molar heat capacity Q of a solid at temperatures close to 0 K and the frequency distribution of black body radiation, originated with Planck. In 1900 he proposed that the microscopic oscillators, of which a black body is made up, have an oscillation frequency v related to the energy E of the emitted radiation by... 

Hydrochloric acid oxidizes zinc metal in a reaction that produces hydrogen gas and chloride ions. A piece of zinc metal of mass 8.5 g is dropped into an apparatus containing 800.0 mL of 0.500 M HCl(aq). If the initial temperature of the hydrochloric acid solution is 25°C, what is the final temperature of this solution Assume that the density and molar heat capacity of the hydrochloric acid solution are the same as those of water and that all the heat is used to raise the temperature of the solution. 

Fig. 4 Rotational contribution to the molar heat capacity C for ortho, para and nominal hydrogen. Note that 1 cal/deg-mol = 4.18 J K Lmor1.

Table 6.1 Comparison of the mean molar heat capacities for carbon dioxide and hydrogen, and carbon monoxide and water...

The importance of the apolar alkyl group is clearly indicated by the change in properties which occur when the terminal methyl groups in (C3H7)4N+ are replaced by OH groups to form (HOCH2-CH2)4N+. The latter shows no exceptional properties because now the ion can hydrogen bond to the solvent (Kay, 1968). However, there still remain many problems to be resolved. For example, no satisfactory explanation has been offered for the various patterns shown by the temperature dependence of the molar heat capacities (Sarma and Ahluwalia, 1973 Sunder et al., 1974). 

Taking the mean molar heat capacities of gaseous hydrogen, iodine and hydrogen iodide as 6.95, 8.02 and 7.14 cal. deg. , respectively, calculate the heat of formation of hydrogen iodide from the gaseous elements at 225 C. The heat of sublimation of solid iodine is 58.5 cal. g. at 25 C. 

Fig. 9,7, The molar heat capacity at constant volume of diatomic gases hydrogen, x nitrogen, O iodine.

The heat capacity and transition enthalpy data required to evaluate Sm T ) using Eq. 6.2.2 come from calorimetry. The calorimeter can be cooled to about 10 K with liquid hydrogen, but it is difficult to make measurements below this temperature. Statistical mechanical theory may be used to approximate the part of the integral in Eq. 6.2.2 between zero kelvins and the lowest temperature at which a value of Cp,m can be measured. The appropriate formula for nonmagnetic nonmetals comes from the Debye theory for the lattice vibration of a monatomic crystal. This theory predicts that at low temperatures (from 0 K to about 30 K), the molar heat capacity at constant volume is proportional to Cv,m = aT, ... 

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