Concentration weight/volume percent

Weight/volume percent is often used for routine laboratory solutions where exact concentrations are not too important. 

Calculate solution concentration in weight/volume percent and weight/weight percent. 

The percent concentration expressed in this way is called weight/volume percent, or % (W/V). Thus... 

It is necessary to change the weight percent concentration to volume percent in order to calculate the cake and filtrate volumes. One kilogram of su ension at 10 wt% soMs contains 0.1 kg of solids and 0.9 kg of liquid. The volume of the suspension is ... 

Calculate solution concentrations in units of molarity, weight/weight percent, weight/volume percent, and volume/volume percent. (Section 7.4)... 

Concentrations of medicinal solutions are sometimes given in terms of weight/volume percent, the mass of solute per 100 ml of solution. The density of dilute solutions is very close to 1 g/mt, so the mass of 100 ml of solution is very close to 100 g. Thus, for solutions of 5% or less, mass percent and weight/volume percent are essentially equal. 

For solutions, however, this concept can be confusing because the units used for the part and the whole are variable. Not only is it common for a solution concentration to be expressed as a volume percent (v/v%) when the solute is a liquid, but it is also cotmnon for the numerator units to be weight units and the denominator units to be volume units (so-called weight/volume percent [w/v%]). 

What is the weight/volume percent concentration of a solution if 2.48 g of solute are dissolved in 600.0 mL of solution ... 

Calculation of Weight/Volume Percent Concentration and Molarity... 

Table 14.2 shows the porosities (pore volume per unit of sample volume) for hydrophilic pores Uphi, hydrophobic pores Upho, and the overall porosity u = Uphi + Upho for Toray paper with two values of PTFE concentrations cptee-Also shown in the table is the parameter hydrophobizing efficiency which represents the ratio of hydrophobic pores (in volume percent) to the PTFE concentration (in volume percent or, as carbon and PTFE have similar density values, in weight percent). This parameter is of importance since high values of the PTFE concentration can lead to an increase in the GDL s ohmic resistance. From the table it can be seen that the PTFE concentration does not significantly influence the volumes of both hydrophilic and hydrophobic pores. At the same time. 

The units of concentration most frequently encountered in analytical chemistry are molarity, weight percent, volume percent, weight-to-volume percent, parts per million, and parts per billion. By recognizing the general definition of concentration given in equation 2.1, it is easy to convert between concentration units. 

Ethanol formulations of salicylic acid (20 and 30%) are used for combination peeling (see salicylic acid section). Trichloroacetic acid is prepared as an aqueous solution, since ethanol solutions do not penetrate the skin. It is prepared by mixing the appropriate concentration of crystals with up to 100 cc of distilled water. Ten and fifteen percent TCA is prepared by mixing 10 or 15 g of crystals in up to 100 cc of total volume, respectively. Aqueous solutions of TCA remain stable for up to 6 months unless contaminated. Other methods have been used to formulate TCA peeling solutions however, the weight/volume methods appear to be the most reliable formulation [5]. Premixed TCA solutions are available from a variety of medical... 

The problems with this approach are 1) without comparing the peaks to a standard or a set of standards, it is not known whether the result is a weight, volume, or mole percent, and 2) the instrument detector does not respond to all components equally. For example, not all components will have the same thermal conductivity, and thus the thermal conductivity detector will not give equal sized peaks for equal concentrations of any two components. Thus, the sum of all four peaks would be a meaningless quantity, and the size of peak B by itself would not represent the correct fraction of the total. 

When a combustible substance is mixed with air, the mixture will explode only when it is neither too rich nor too lean. The lower explosion limit (LEL) is the minimum volume percent of the substance in air with flammability, which is separated from the upper explosion limit (UEL) by the explosive concentration range. The tabulations in handbooks are based on experimental data, and sometimes derived from estimation methods based on the elemental composition of the fuel as CmEtxOy. Figure 6.11 shows the LEL for the series of normal paraffins and of 1-alcohols versus the number of carbon atoms. There are two ways to plot the results, which show that, for paraffins, the volume percent shows a steeply declining trend, but the weight percent shows a mildly increasing trend. One may conclude that a smaller volume percent of higher paraffin... 

The concentrations are volume or mole percent or parts-per-mill-ion (v/v). This is the usual method of presenting gas concentrations as opposed to those on a weight basis. The container must be thoroughly mixed to ensure homogeneity. The two major sources of error of this technique come from lack of good mixing and not... 

For each ingredient, the concentration expressed as percent weight/weight, percent volume/volume, or percent weight/ volume must be indicated... 

The best deposits of all six insecticides studied—dieldrin, lindane, endrin, dinitrocresol, heptachlor, and DDT—produced 50% mortality with exposure periods of less than 2 minutes (LT50). All mortality estimates were based on a 72-hour post treatment holding period at about 70 °F. and 60% relative humidity. Lindane and dieldrin were the most toxic. One percent solutions produced 50% mortality with less than 2-seconds exposure (Table I). [1% solutions weight/volume lOmg./ml. = 1% this applies to all further references to concentration.] This left little doubt that surface deposits could be made toxic enough by contact to kill bark beetles in nature even though they may be in contact with the bark surface of their host trees for as little as 1 minute or less. 

Uniformity of lower limits on a mass basis. Concentrations of vapors and gases usually are reported in volume percent. As molecular weight increases, the lower limit usually decreases. On a mass basis, the lower limits for hydrocarbons are fairly uniform at about 45 mg/L at 0°C and 1 atm. Many alcohols and oxygen-containing compounds have higher values for example, on a mass basis, ethyl alcohol in air has a lower limit of 70 mg/L.27... 

The density system is used in a number of countries to determine alcohol concentration. The United States uses a simpler proof system based on 100% alcohol being equivalent to 200° proof. Fractions of this concentration, by volume, are specified by multiplying the concentration, in percent by volume, by two (Table 16.10). In France, alcohol concentrations in spirits are simply specified as percent alcohol by volume, sometimes referred to as the Gay-Fussac system. Percent alcohol by weight is used in Germany. 

As mentioned earlier, we sometimes conduct an alkalinity scan by changing alkali concentration while the salinity is fixed. Then the activity map can be presented by alkali concentration versus oil volume percent or the ratio of oil volume percent to surfactant volume or weight percent, schematically shown in Figure 12.5. 

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