Molar mass from titration

Simple) methods that provide an indication of the molar mass from the polymer melt (e.g. various methods related to the melt viscosity) are likely to retain a position of prominence in industrial practice. Very simple, low-cost methods, such as titration and osmometry, are also likely to prevail. More-complex methods, such as light scattering, are increasingly replaced by (or combined with) SEC. 

The titration vessel was purged with nitrogen to eliminate CO 2. From the volume and molarity of added base and the mass of titrated DOC, the content of acidic functional groups can be calculated. Carboxylic acid content was calculated from the amount of base added until the end-point was reached. Phenolic acid content was calculated as twice the difference in titrant required to change the pH of the titrate from 8 to 10, since it was assumed that at pH 10 only half the phenolic groups were dissociated. A solution of a concentration of 20 mgL" as DOC NOM were titrated. The error due to the salt content of NOM is likely to be high. 

Polysalt formation, as described in the previous section, is a special case of titration of polyelectrolytes. These acid-base reactions also exhibit some special differences from the corresponding phenomena with regard to low-molar-mass compounds. 

Sodium hydroxide is one of the bases commonly used in the laboratory. However, it is difficult to obtain solid sodium hydroxide in a pure form because it has a tendency to absorb water from air, and its solution reacts with carbon dioxide. For these reasons, a solution of sodium hydroxide must be standardized before it can be used in accurate analytical work. We can standardize the sodium hydroxide solution by titrating it against an acid solution of accurately known concentration. The acid often chosen for this task is a monoprotic acid called potassium hydrogen phthalate (KHP), for which the molecular formula is KHC8H4O4 (molar mass = 204.2 g). KHP is a white, soluble solid that is commercially available in highly pure form. The reaction between KHP and sodium hydroxide is... 

A 0.552 g sample of ascorbic acid (vitamin C) was dissolved in water to a total volume of 20.0 mL and titrated with 0.1103 M KOH. The equivalence point occurred at 28.42 mL. The pH of the solution at 10.0 mL of added base was 3.72. From this data, determine the molar mass and for vitamin C. 

The determination of the functionality is an essential parameter in block polycondensation. Unfortunately, many of the values given in the literature are doubtful because they are obtained by only one analytical technique or they are implicitly assumed. Only the comparison of the molar masses obtained by direct determination (chromatography, tonometry, mass spectrometry, osmometry) and those calculated from the concentration of the end-groups is relevant. The latter is determined by e.g., chemical titration, NMR, or infrared spectroscopy the use of several methods increases the accuracy of the values. Reliable values are obtained when both direct and indirect determinations are taken into account. 

The procedure called titration can be used to standardize a solution of a base, which means determine its molar concentration. To standardize a base, a solution of the base with unknown molarity is gradually added to a solution containing a known mass of an acid. The procedure enables you to determine when the number of moles of added OH- ions from the base equals the number of moles of H+ ion from the acid. 

Fig. 2.7 ESI mass spectra of ligands present in CPC spin column eluates have a linear response with increasing concentration ESI (positive ionization mode) mass spectral analysis of the eluate from the CPC spin column titration ofWY252 (MW 457 Da) with MM P-1 where the molar ratios of MM P-1/ WY252 are constant at 1 5 while their individual concentrations linearly increase. The volume injected for each sample was...

XH NMR experiments show that the viologen residue interacts effectively with the CB7 host [53], Voltammetric and mass spectrometric data are also consistent with the formation of inclusion complexes between the dendronized viologens and CB7. As was the case with methylviologen, complexation by CB7 depresses the molar absorptivity coefficient for the viologen UV absorption band and this effect can be conveniently utilized to fit the absorbance data in titration experiments to 1 1 binding isotherms. From the optimization of these fittings we obtained the corresponding equilibrium association constants (Table 3). 

The units that chemists and engineering specialists most frequently use to quantify the concentration of acids and bases in a solution are molar, molal, and normality. The concentration unit that plant engineers commonly use is weight or mass fraction. However, since what is shown on process flow sheets and the specifications for control valves are reagent and influent flows, it is desirable to be able to convert from any of these concentration units to flow units. It will be shown in the remainder of the text how valuable it will be for control valve sizing and pH system analysis to have the ratio of reagent to influent flow as the abscissa of the titration curv e. 

Weigh out accurately about 0.9 g of the blue crystals. Dissolve in dilute sulphuric acid and make up to 2S0 cm with the acid in a volumetric flask. Pipette 25.0 cm of the solution into a conical flask, add an equal volume of the acid and titrate with standardised (about 0.02 M permanganate) until a drop produces a faint permanent pink colour superimposed on a faint yellow. Repeat to obtain concordant results and calculate from the average titre the molar concentration of VOSO4 and its mass. Hence calculate x in the formula. 

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