Percentage Composition by Volume

The concentration is expressed in terms of volumes of the solute and solvent. 

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A mixture ofN2 and H2 jjas a density ofO 267 g/hter at 700 torr and 30°C por this mixture, calculate (a) the apparent molecular weight, (b) the percentage composition by volume, and (c) the number of molecules in one ml... 

Fig. 8.17 AC conductivity versus frequency for a variety of carbon-black composites O crosslinked EBA with 8.3% acetylene black (AC), thermoplastic EBA with 11.3% AC, + thermoplastic EB with 14.5% AC, EBA particulate composite with 9.1% AC, EBA particulate composite with 10.7% AC, O blended PE with 9.2% AC, blended PE with 11.1% AC, A EPDM with 15.2% furnace black (FB), EPDM with 21.1% FB and EPDM with 26.3% FB (all percentages are by volume). Reproduced with permission of the Institute of Physics from Jager et al. (2001).

The underground gas composition is usually expressed in fractions or percentage points by volume. But grammoles of different gas components in conditions close to standard occupy practically the same volume, 22.414-10" m That is why molar fractions of gas components in the composition of a underground gas C are equal to their volume fractions C>,... 

The empirical formula of an organic compound can be obtained from its percentage composition by mass. For compounds that contain only carbon, hydrc en and oxygen this can be found in a quantitative combustion experiment in an excess of oxygen. The number of carbon atoms in an organic molecule can be calculated if the volume of carbon dioxide produced by complete combustion of a known volume of pure gaseous compound is measured (Chapter 1). 

Answer "Composition by volume is a poor expression, although it is universally used. As we stated earlier, each component of a gaseous mixture occupies the entire volume, not a percentage of it. What the expression really means is composition by number of molecules. Thus, 78.1% of the molecules are nitrogen, 20.9% are oxygen, etc. Since the pressure is proportional to e number of molecules, the so-called proportion by volume is also the proportion by pressure, or... 

Predicted results for E2 are plotted in Figure 3-10 for three values of the fiber-to-matrix-modulus ratio. Note that if Vj = 1, the modulus predicted is that of the fibers. However, recognize that a perfect bond between fibers is then implied if a tensile <32 is applied. No such bond is implied if a compressive 02 is applied. Observe also that more than 50% by volume of fibers is required to raise the transverse modulus E2 to twice the matrix modulus even if E, = 10 x E ,l That is, the fibers do not contribute much to the transverse modulus unless the percentage of fibers is impractically high. Thus, the composite material property E2 is matrix-dominated. 

One of the important factors affecting composite properties is the amount of fiber it contains, i,e., percentage by volume. 

Chemistry is a quantitative science. This means that a chemist wishes to know more than the qualitative fact that a reaction occurs. He must answer questions beginning How much. . . The quantities may be expressed in grams, volumes, concentrations, percentage composition, or a host of other practical units. Ultimately, however, the understanding of chemistry requires that amounts be related quantitatively to balanced chemical reactions. The study of the quantitative relationships implied by a chemical reaction is called stoichiometry. 

In a test on a furnace fired with natural gas (composition 95 per cent methane, 5 per cent nitrogen) the following flue gas analysis was obtained carbon dioxide 9.1 per cent, carbon monoxide 0.2 per cent, oxygen 4.6 per cent, nitrogen 86.1 per cent, all percentages by volume. 

The symbols used in this column to denote non-aqueous solvents are given in the list of abbreviations. The entry "HgO" denotes an aqueous solution an entry like "MeCN11 denotes a solution in the nominally pure (and anhydrous) solvent given in one like "MeCN 50" the number denotes the percentage (by volume, unless otherwise specified) of the non-aqueous solvent given in a solvent mixture of which the balance is understood to be water. An occasional entry like "EtOH (aq)" reflects our inability to deduce the composition of the solvent mixture from the published Information given, and appears only when the importance of the data seemed to us to override the laxity of the reporting. Of the entries... 

Table 7.3 Calculated mass balance and compositions by weight and by volume for a 14-month-old cement paste (w/c = 0.5) Percentages on the ignited weight for material equilibrated at 11% RH... 

The composition of a gas derived by the gasification of coal is by volume percentage carbon dioxide 4, carbon monoxide 16, hydrogen 50, methane 15, ethane 3, benzene 2, balance nitrogen. If the gas is burned in a furnace with 20% excess air, calculate... 

The composition of the feed was adjusted to contain about 1.5% by volume n-butane in air, and hence below the lower explosion limit of this mixture. The butane and oxygen conversions are reported as the mole percentages of each in the feed, converted to products. The yields of carbon containing products are defined as the mole percentages of n-butane converted to the respective products. The selectivity of each product is defined as the ratio of the yield of each product divided by butane conversion. The carbon, hydrogen and oxygen balances are 100 +/- 5 %, and all results are normalized on a no loss carbon basis. Blank runs over acid-washed quartz chips showed no reaction under conditions similar to those made with the catalyst. 

When compositions are quoted as percentages it is important to know whether these are by mole, weight-by-weight (w/w), volume-by-volume (v/v) or weight-by-volume (w/v) and, in the last case to appreciate that the sum of the components will not add up to 100. 

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