In Stewart’s approach to body fluids as physico-chemical systems of interacting chemical species, three conditions have to be maintained, based on which Stewart found out six simultaneous equations which he solved with a 4th order polynomial equation, and hence three independent variables (pCO2, Atot and SID) determing the pH of a solution were obtained. Which of the following is not one of the three conditions?
A. Electrical neutrality must be present in the solution
B. Conservation of mass must occur
C. All dissociation equilibria must be satisfied simultaneously
D. All reactions must take place at body temperature
Answer: D
A Java Applet is available here on the web to give you an idea of how the 3 independent variables affect the pH of a solution.