Equivalent mass

The equivalent mass of a substance is the mass in grams of 1 equiv of the substance. The equivalent mass is often a useful property to characterize a substance. 

EXAMPLE 15.20. A new solid acid was prepared in a laboratory its molar mass was not known. It was titrated with standard base, and the nnmber of moles of base was calcnlated. Without knowing the formnla of the acid, can you teU how many moles of the acid were present in a certain mass of acid Can you tell how many eqnivalents of acid were present  

Withont knowing the formula, you cannot tell the number of moles, but you can tell the nnmber of equivalents. For 

One mole of HX is 36 g 0.500 mol of H2X2 is also 36 g. Yon cannot tell from the mass which is the formula of the acid. In either case, the eqnivalent mass of the acid is 36 g per eqnivalent. The eqnivalent mass of H2X2 is given by 

To convert from molar mass to equivalent mass, use the same factors as were introduced in Sec. 15.4. 

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TNT Equivalence. Explosion strength is often expressed as equivalent mass of TNT in order to permit estimates of possible explosion damage. For BLEVEs and pressure vessel bursts, using this equivalence is unnecessary because the methods mentioned above give explosion blast parameters which relate directly to the amount of possible damage potential. However, the concept of TNT equivalence is still useful because it appeals to those who seldom deal with blast parameters. For reasons explained in Section 4.3.1, BLEVEs or pressure vessel bursts catuiot readily be compared to explosions of TNT (or other high explosives). Only the main points are repeated here. 

In the method which will be presented in Section 6.3.3., the blast parameters of pressure vessel bursts are read from curves of pentolite, a high explosive, for nondimensional distance R above two. For these ranges, using TNT equivalence makes sense. Pentolite has a specific heat of detonation of 5.11 MJ/kg, versus 4.52 MJ/kg for TNT (Baker et al. 1983). The equivalent mass of TNT can be calculated as follows for a ground burst of a pressure vessel ... 

G,. = equivalent mass flow inside tubes, Ib/hr (ft of flow cross section)... 

In addition Faraday recognized that, for different electrode reactions and the same amount of charge, the ratio of the reacting masses is equal to the ratio of the equivalent masses ... 

The results of this analysis are shown in Figure 5.16, which contains the UV trace, at 220 nm, and the equivalent mass spectral trace. In this case, the mass spectral data are represented by a modification of a reconstructed ion chromatogram (RIC) known as the base-peak trace, i.e. a plot of the intensity of the base peak in each scan (the m jz value of this may well vary from scan to scan) as a function of time. 

In the past the parameter Vzj moles of a given ion j had been called the ion s chemical dissociation equivalent, and the corresponding mass Mj/zj (where Mj is the molar mass) was called the ion s equivalent mass. The ion s equivalent concentra-... 

The parameter Vj/n mol, which can be written for each component of the electrode reaction, is sometimes called the chemical equivalent of the component in the reaction named, and the value of (Vjln)Mj is called the equivalent mass (see the discussion of chemical equivalent in Section 1.3). 

Any existing source of the steel basis material subcategory that introduces pollutants into a POTW must achieve the pretreatment standards listed in Table 8.21 A. In cases where a POTW finds it necessary to impose mass effluent pretreatment standards, the equivalent mass pretreatment standards are provided in Table 8.21B.3 7... 

Experiments with explosives have demonstrated16 that the overpressure can be estimated using an equivalent mass of TNT, denoted mTNT, and the distance from the ground-zero point of the explosion, denoted r. The empirically derived scaling law is... 

TNT equivalency is a simple method for equating a known energy of a combustible fuel to an equivalent mass of TNT. The approach is based on the assumption that an exploding fuel... 

Estimate the explosion efficiency, and calculate the equivalent mass of TNT using Equation 6-24. 

Zeolites exhibit a considerably lower proton (acid site) concentration than liquid acids. For example, 1 g of H2SO4 contains 20 X 10-3 moles of protons, whereas 1 g of zeolite HY, with a Si/Al atomic ratio of five, contain no more than 3 X 10-3 moles of protons. (Note that this is a cmde approximation of the acidic sites available for catalysis, because it assumes that with both materials all protons are available and catalytically active.) Moreover, 1 g of H2SO4 occupies far less volume (i.e., 0.5 cm3) than the equivalent mass of zeolite (4-6 cm3). 

Previous studies of Vapor Cloud Explosions (VCE) have used a correlation between the mass of a gas in the cloud and equivalent mass of TNT to predict explosion overpressures. This was always thought to give conservative results, but recent research evidence indicates that this approach is not accurate to natural gas and air mixtures. The TNT models do not correlate well in the areas near to the point of ignition, and generally over estimate the level of overpressures in the near field. Experiments on methane explosions in "unconfined" areas have indicated a maximum overpressure of 0.2 bar (2.9 psio). This overpressure then decays with distance Therefore newer computer models have been generated to better simulate the effects... 

In an experiment to determine the equivalent mass of an unknown acid, a student measured out a 0.250-gram sample of an unknown solid acid and then used 45.77 mL of 0.150 M NaOH solution for neutralization to a phenolphthalein end point. Phenolphthalein is colorless in acid solutions but becomes pink when the pH of the solution reaches 9 or higher. During the course of the experiment, a back-titration was further required using 1.50 mL of 0.010 M HC1. 

In Part II, a weak acid is titrated with the strong base from Part I and the equivalence point will be somewhat higher than 7 (8 - 9). By titrating a known amount of solid acid with the standardized NaOH, it will be possible to determine the number of moles of ff the acid furnished. From this information, one can obtain the equivalent mass (EMa) of the acid ... 

However, the equivalent mass of the acid may or may not be the same as the molecular mass of the acid since some acids produce more than one mole of ff per mole of acid. In order to find the molecular mass from the EMa, the molecular formula is required. 

Once the student had determined the exact concentration of the base, the student then proceeded to determine the equivalent mass of an unknown acid. To do this, the student measured out 0.500 grams of an unknown solid acid and titrated it with the standardized base, recording pH with a calibrated pH meter as the base was added. The student added 43.2 mL of the base but went too far past the end point and needed to back-titrate with 5.2 mL of the 0.100 M HC1 to exactly reach the end point. 

Epoxidation catalysts, organic titanium compounds as, 25 135 Epoxide determinations, 10 385 Epoxide equivalent mass (EEM), 10 355 Epoxide equivalent weight (EEW), 10 355, 361-363, 385... 

Here CA is the equivalent mass fraction of acetyl, and the rate constant varies with T as... 

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