THE DRIVING ENERGY OF PHYSICO-CHEMICAL 



REACTION, AND ITS TEMPERATURE 



COEFFICIENT. 



Bv Theodore William Richards. 



Received April 10, 1900. Presented April 11, 1900. 



Every beginner in Physical Chemistry of course notices the similarity 

 in form of the equations of Clausius and van't Hoff, ~~pfT — n w> 

 and — —■ — rr • The differences in the interpretation of the sym- 



< ' 1 ill 



bols are the only hindrance to the welding of the two equations into 

 one. P usually consists of a single quantity, a pressure, while K is 

 usually a product of concentrations. On the other hand, the second 

 member of the equation sometimes includes work (A = A — U) and 

 sometimes contains simply the diminution of the internal energy (U) 

 of a process conducted at constant volume. 



Since these distinctions are so confusing that errors from the lack of 

 proper discrimination have crept into some of our best and most helpful 

 treatises, the present paper, which is a treatment of the subject from a 

 single point of view, may be of assistance to students who have not mas- 

 tered the matter. I have found it advantageous, both in teaching and in 

 thinking, to look at the whole field from the point of view of pressure. 

 This practice has recently received support in an interesting article by 

 Arrhenius * on the speed of reactions. 



That the pressures affecting a given reaction should exert the deciding 

 influence in determining the magnitude and direction of a chemical change, 

 is no more astounding than that the resultant of mechanical forces should 

 be the agent determining the change of position of finite masses. Hence 

 the consideration of pressure, which has the dimensions of an intensity, 

 seems to be a more direct method of studying the progress of a reaction 



* Zeitschr. phys. Chem. 28, 317 (1899). 



