Ammonia specific heat

Assume that all species are highly dilute in ammonia. For the purpose of this problem, consider the following transport properties as constants n = 2.7 x 10-4 g/cm-s, k = 1.1 x 104 erg/cni S-K, and Dtmg-nh3 = 3 cm2/s. The specific heat for ammonia may be taken as cp = 2600 J/kg-K. Assume that the density may be determined from a perfect-gas equation of state for ammonia alone. 

The anhydrous salt yields yellowish-white crystals of density2 7-3 at 15° C. and melting point 3 1042° C. The specific heat is 4 0-0728 and the molar heat 05-4. The index of refraction is 2 2-14. It is insoluble in water, aqueous ammonia and in solutions of ammonium salts,5 and only slightly soluble in aqueous alkali or brine.6 It is decomposed when heated with hydrogen chloride,7 forming lead and arsenic chlorides, and in hot nitric acid it dissolves to form arsenic acid and lead nitrate, the latter being precipitated if the acid is sufficiently concentrated.8... 

Reference TDI contains an enthalpy table for ammonia at different pressures. Reference TD2 contains a series of tables in an appendix from which the specific heats of the reaction-gas mixture were calculated. Humidity charts were also useful. Reference TD3 is valuable for its steam tables, while Ref. TD4 contains both thermodynamic and chemical equilibria data for nitric acid. The final reference, Robertson and Crowe (Ref. TD5), contains formulae and tables for the sizing and choice of an air-feed compressor. 

The specific heat of water is abnormally high, and this fact has an enormous influence upon climate and geological phenomena. Liquid ammonia is the only liquid possessing a higher specific heat. 

Assuming ammonia to be an ideal gas in the range 300 - 2000 K the following Equation (2) represents the specific heat ... 

Table 3. Specific heat of ammonia at constant pressure in kj kg 1 K 1... 

They then used the values given in the International Critical Tables for the heats of formation of ammonium bromide, sodium amide, and sodium bromide, together with heats of solution which they determined, to obtain 17 00 kcal for the heat of formation AH) of liquid ammonia at -33 4° G. This they combined with the heat of vaporization and specific heat data to obtain A///-(NH3 g) =-10 93 kcal at 0° G, in good agreement with Haber. On the other hand Becker and Rothes interpreted the data of Kraus and Ridderhof to yield 11 64 kcal mole i for AHf at 20° G. In any case whichever interpretation is correct, this method is not an absolute one for determiniiig the heat of formation of ammonia because the determined heats of formation of ammonium bromide and of sodium amide themselves involve a knowledge of the heat of formation of ammonia. For example, the... 

The values of cr" (the sp. ht. of saturated vapour) were calculated it is negative. The specific heats (joules/I° g.) of superheated ammonia vapour were... 

Physical properties of ammonia at the mean temperature of 80°C specific heat 2.418 kJkg °C, thermal conductivity 0.0317 Wm °C, density... 

In fact we find that real gases do not exhibit this behaviour and the specific heat is not equal to that of the perfect gas. For example, fig. 11.3 shows the molar heat capacity Cy of ammonia as a function of T and p. 

Ratio of specific heat capacities (Cp/C ) = 1.33 Molecular weight of ammonia = 17.03... 

On the other hand in the case of steam, alcohol, carbon bisulphide, as well as in the case of fluids commonly used in refrigerating machines, etc, carbon dioxide and ammonia, the behaviour is different In these latter cases the specific heat of the saturated vapour remains neg ative throughout the whole range of temperature up to the critical point, at which point its negative value becomes infinite... 

Monoclinic prismatic crystals from water or alcohol, mp 209.5. dj5 1.400. Eutectic with cyanamide at 35.6 (15% dicyanodiamide). Specific heat 0.456 at 0-204 . Neutral reaction. Soly in water at 13 2.26%, more sol in hot water. Solns above 80s dec slowly, yielding ammonia. Soly in abs ethanol at 13 1.26% in ether 0.01%. Insol in benzene, chloroform. Sol in liq ammonia. 

---