Equivalent weight EW

Normality is the number of equivalent weights (EW) per unit volume and, like formality, is independent of speciation. An equivalent weight is defined as the ratio of a chemical species formula weight (FW) to the number of its equivalents... 

Since the actual number of protons transferred between the analyte and titrant is uncertain, we define the analyte s equivalent weight (EW) as the apparent formula weight when = 1. The true formula weight, therefore, is an integer multiple of the calculated equivalent weight. 

Figure 8. Hydration isotherm for Nation 117 (equivalent weight (EW) of 1100 g/equiv) and the distribution of the dielectric constant and protonic charge carrier concentration across the hydrated hydrophilic channels (pores) for three different water contents (top).

Equivalent Weight and Volume an d Their Precision Indexes for Comparison of Explosives in Air. Data for mean peak pressures and positive impulses determine figures of merit which express performances of expls fired in air. Equivalent Weight (EW) Equivalent Volume (EV) are easily interpretable by ordnance designers. The EW of a new expl is the ratio of wt of a known expl to the wt of a new expl which gives. equiv power as measured by peak pressure or positive impulse. The EV is similarly defined... 

The term equivalent weight (EW) is given to the factor of the molecular weight/functionality. The functionality is the number of appropriate active sites in the molecule. 

The validity of MD simulation is impacted by the choice of system, interaction potential and algorithm implemented. We first discuss the choice of system. In this work we chose to simulate Nafion with an equivalent weight (EW) of 1144 g/mol, which is a practically reasonable EW. In order to have a direct comparison of the effect of side chain length, SSC PFSA polymer electrolyte was simulated with an EW of 978 g/mol. (Commonly used SSC iono-mer has an EW 800 g/mol). The repeat units of these PFSA membranes are shown in Fig. 3. These two materials have the same backbone separating side chains thus the only differentiating feature is side chain length. 

Another finding reported by DuPont is that the equivalent weight (EW) exhibits a pronounced influence on performance and methanol permeation. Whereas the highest performances were found with low EW membranes, the membranes with high EW had the lowest relative methanol permeation (Figure 27.24). According to DuPont, a 2 mil experimental membrane is in development which exhibits better performance for DMFCs compared to the 7 mil commercial membrane. 

Membrane Type Membrane Equivalent Weight (EW) (g equiv ) Thickness (mm)... 

Recent SAXS work by Wu [56] has demonstrated that the ionic domains in Nafion membranes are most probably spherical and exhibit a size distribution and spacing that does not vary much with equivalent weight (EW). The latter work suggested that strings of smaller spherical aggregates could be sufficiently close to coalesce upon swelling with water uptake by the membrane, and thus could provide percolation pathways for ionic transport. This picture could replace the nanoscale (1.2 nm-wide) channels suggested in earlier models for Nafion to explain transport phenomena. 

To calculate N, we need to know the weight of dissolved solute and its equivalent weight, EW. 

The performance of P EMs can be characterized by either their electrochemical parameters, which include their equivalent weight (EW) and proton conductivity, or by their physical properties, which include thickness, gas permeability, mechanical strength, water uptake, and swelling, and so on. 

The amount of ionic groups in these membranes is conventionally expressed in terms of the equivalent weight (EW) of the polymer." EW is defined as the weight of polymer which will neutralize one equivalent of base. It is inversely proportional to the ion-exchange capacity (lEC) according to the following relationship ... 

The solubility parameter of Nafion membranes has been determined experimentally in a recent study (3) The samples which have been studied have an equivalent weight (EW) of either 1100 or 1200 (weight of polymer per sulfonic acid group). Since the samples are not soluble, the solubility parameter of the polymer can be determined only from the swelling technique (40 ... 

Measurements of the 120, 214 and 295 duPont Nafion films and also fully converted ethylene diamine films are considered to be typical. The 120 polymer is a homogeneous film 10 mils thick of 1200 equivalent weight, (ew), perfluorosulfonic acid resin. The 214 and 295 films are each of 7 mils thick resin of 1150 ew having one surface facing the cathode that has been chemically modified to 1.5 mils depth, and having T-24 backing. The 295 films are the same as the 214 except that they are modified to a 1.5 mil depth and have T-900 backing (17) (18). 

The equivalent weight (EW) [1, 22] of an oligo-polyol is defined as the oligo-polyol MW divided by its functionality ... 

Normality (N). Number of equivalents of solutes per liter of solution Equivalents of solute. Weight (g) of solute/equivalent weight (EW) of the solute, where EW = MW/n n = number of H+ (for acids) and OH (for bases) per molecule of oxidation-reduction reactions, number of electrons gained per molecule. 

The wettability or the water content of a membrane depends on the equivalent weight (EW) or the ion-exchange capacity (IEC), pretreatment, solution composition, operating temperature, etc. The equivalent weight is defined as the weight of the polymer which is neutralized by one equivalent of alkali and is the reciprocal of IEC as... 

Sulfonated PTFE, Nation membrane, of equivalent weight (EW) of 1100 ... 

While the focus of the model performance assessment was on Nafion 1100 equivalent weight (EW), the binary friction membrane transport model is quite general and should be applicable to other PFSA membranes. This is supported by preliminary results in applying the model to Dow membranes and membrane C, whereby rational changes in a single model parameter based on physical considerations of structural differences from Nafion yield conductivity predictions that are in good agreement with experimental measurements [61]. 

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