Thermochemistry Conservation of Energy in Chemical Reactions

Using this expression in (2.3.14) we arrive at the conclusion that if the propagation of sound is an adiabatic process, then the velocity Csound is given by 

Experimental measmements of sound velocity confirm this conclusion to a good approximation. 

Hess s work was not very well known for many decades after its publication. The fundamental contribution of Hess to thermochemistry was made known to the chemists largely through Wilhelm Ostwald s (1853-1932) Textbook of General Chemistry, published in 1887. The above statement, known as Hess s law, was amply confirmed in the detailed work of Marcellin Berthelot (1827- 

Germain Henri Hess (1802-1850) (Courtesy the E. F. Smith Collection, Van Pelt-Dietrich Library, University of Pennsylvania) 

1907) and Julius Thomsen (1826-1909) [11]. As we shall see below, Hess s law is a consequence of the law of conservation of energy and is most conveniently formulated in terms of a function of state called enthalpy. 

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