Conversion molar mass

Mechanistic studies on the formation of PPS from polymerization of copper(I) 4-bromobenzenethiolate in quinoline under inert atmosphere at 200°C have been pubUshed (91). PPS synthesized by this synthetic procedure is characterized by high molar mass at low conversions and esr signals consistent with a single-electron-transfer mechanism, the Sj l-type mechanism described earlier (22). 

As you will see shortly, the formula of a compound can be used to determine the mass percents of the elements present. Conversely, if the percentages of the elements are known, the simplest formula can be determined. Knowing the molar mass of a molecular compound, it is possible to go one step further and find the molecular formula. In this section we will consider how these three types of calculations are carried out. 

The Mole, Molar Mass, and Mole-Gram Conversions... 

The molar mass distribution of hyperbranched polymers is, therefore, always larger than diat of titeir linear homologues and tends toward infinity when conversion becomes close to 1. The use of a B3, comonomer, acting as a chain limiter and core molecule, helps in reducing polydispersity and controlling the molar mass of the final polymer.197... 

This dicarboxy-terminated oligomer is prepared by reacting excess adipic acid with 1,2-edianediol in die bulk until hydroxyl group conversion is complete (Scheme 2.47). The molar mass of final polymer depends on the initial molar ratio of monomers (procedure similar to that described in ref. 401). 

A chemical equation tells us the relations between the amounts (in moles) of each reactant and product. By using the molar masses as conversion factors, we can express these relations in terms of masses. 

Gelation occurs at relatively low conversions of monomer to polymer hence the number-average molar mass at the gel point is low. By contrast, however, the weight-average molar mass becomes infinite at the gel point. 

Another commercially important crosslinking process that involves unsaturated polymer precursors is the so-called drying of alkyd resins in paints. This process is not drying at all, at least not in the sense of mere loss of solvent to leave behind a solid residue. Instead, the main process is the conversion of high relative molar mass molecules to a crosslinked structure via... 

An enzyme obtained from human plasma by conversion of profibrinolysin with streptokinase to fibrinolysin. Proteolytic enzyme of unknown structure molar mass = 75000. 

In all calculations the molar masses given in the top of Table I were used. First of all, the effects of variations in the concentration of trifunctional monomers were determined, as exemplified by the nine formulations of Table I and the resulting prepolymer characteristics after full conversion given in Table II. Formulations FIO to F40 result in branched prepolymers, which are cured in the third stage by difunctional monomers. On the other hand, formulations FOO to F04 result in the same linear prepolymer, which is subsequently cured with various mixtures of di- and trifunctional monomers. The number average functionalities of PI (and P2) and of the mixtures of E and F monomers are varied systematically between 2.0 and 2.4. Therefore, the only difference between formulations FjO and FOj is the stage in which the branching units are added. 

Figures 2 and 5 show the increase of the mass average molar mass, R i, with conversion for the systems with branched and linear prepolymers, respectively. These results indicate that addition of the branching monomer in the first stage yields much higher values of R, and the gel point is reached at lower conversion than addition in the third stage. Translated into practical properties this means that the processing and application qualities (e.g. flow) of a paint based on formulation F40 will be inferior to those of one on the basis of for-...

Molar mass can be thought of as a conversion factor between mass in grams and number of moles. These conversions are essential in chemistry, because chemists count amounts of substances in moles but routinely... 

Avogadro s number and molar mass make it possible to convert readily among the mass of a pure element, the number of moles, and the number of atoms in the sample. These conversions are represented schematically in the flowchart shown in Figure 2-22. 

Sometimes chemists have to analyze substances about which they know very little. A chemist may isolate an interesting molecule from a natural source, such as a plant or an insect. Under these conditions the chemical formula must be deduced from mass percentage data, without the help of an expected formula. A four-step procedure accomplishes this by using mass-mole conversions, the molar masses of the elements, and the fact that a chemical formula must contain integral numbers of atoms of each element. 

As with all calculations of chemical amounts, we must work with moles. Because grams are asked for, we must do a mole-mass conversion this requires the molar mass of the substance, which in turn requires that we know the chemical formula. 

Lewis and Randall stated that in dilute solutions the activity coefficient of a strong electrolyte is the same in all solutions of the same ionic strength this statement was confirmed in thermodynamic deductions of activity coefficients. The molality version of 7 can be applied in a fully analogous way and allows a more straightforward treatment of solution properties. [Conversion of molality into molarity requires the solution densities e.g., for a solute of molar mass M and a solution of density q we have... 

In 1994, we reported the dispersion polymerization of MM A in supercritical C02 [103]. This work represents the first successful dispersion polymerization of a lipophilic monomer in a supercritical fluid continuous phase. In these experiments, we took advantage of the amphiphilic nature of the homopolymer PFOA to effect the polymerization of MMA to high conversions (>90%) and high degrees of polymerization (> 3000) in supercritical C02. These polymerizations were conducted in C02 at 65 °C and 207 bar, and AIBN or a fluorinated derivative of AIBN were employed as the initiators. The results from the AIBN initiated polymerizations are shown in Table 3. The spherical polymer particles which resulted from these dispersion polymerizations were isolated by simply venting the C02 from the reaction mixture. Scanning electron microscopy showed that the product consisted of spheres in the pm size range with a narrow particle size distribution (see Fig. 7). In contrast, reactions which were performed in the absence of PFOA resulted in relatively low conversion and molar masses. Moreover, the polymer which resulted from these precipitation... 

It is well-known that the coil density of macromolecules decreases with increasing molar mass. Due to cyclization this decrease in density becomes less or even disappears because the macromolecules of higher molar mass are more strongly contracted than those of lower molar mass. After a certain conversion of pendant vinyl groups, the influence of the intermolecular reaction on [r ]... 

Fig. 40. A Relation between [-r ] and Mw during crosslinking of PVS. B Increase of Mw with the conversion of pendant vinyl groups during crosslinking of PVS. Molar mass of starting PVS, Mw0 = 135000 g/mol. Temperature = 70 °C. The PVS concentrations are shown in the figures [217].

Fig. 41. Initial rate of the conversion of pendant vinyl groups during crosslinking of PVS shown as a function of the volume fraction of methanol in the toluene/methanol mixture [217]. PVS concentration = 0.30-0.35 mass %, initial molar mass of PVS = 170000 g/mol, temperature = 70 °C.

A Both the density and the molar mass of Pb serve as conversion factors. 

IB For one conversion factor we need the molar mass ofMgCl2. 

B We need the molar mass of ethyl mercaptan for one conversion factor. 

A The molar mass of halothane is given in Example 3-3 in the text as 197.4 g/mol. The rest of the solution uses conversion factors to change units. 

B Care must be taken to use the proper units/label in each conversion factor. Note, you cannot calculate the molar mass of an impure material or mixture. 

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