Nonideality, conventions used define

Conventions Used to Define Nonideality. The equations developed in the preceeding section for the ideal case have really crystallized our operational definition of ideal conditions, since they require (1) that S/AnBm/ /Awt/Bm = 1 at all concentrations, and (2) that the experimental techniques give us a measure of cMweq or its analogs, such as (X i2CiMi)eq... 

For nonideal gases the above simplifications are not applicable and it would appear to be best to use equation (21) directly as the chemical equilibrium condition. However, it is conventional when dealing with nonideal gases to replace p,- by the fugacity defined below. By solving equation (15) for Ni and using equation (25) to express Ni in terms of p, it is found that... 

At pH 7, where H = OH, the voltage from the electrode is zero. This is called the isopotential point (Fig. 4). In theory, this point is temperature-independent. The International Union for Physical and Applied Chemistry (lUPAC) (1) operational pH scale is defined as fhe pH relative to a standard buffer measured using a hydrogen electrode. In practice, a pH electrode is calibrated with standard buffers of pH 7.00 and pH 4 or 9 fo defermine the isoelectric point and slope, respectively. Conventional pH meters will read accurately over a range of 2.5-11 and beyond these ranges, accuracy cannot be assured. However, recently, instruments have become available that carry out calibration to allow correction for nonideal electrode behavior allowing accurate measurements between ranges of pH 1 and 13. 

---