Benzene freezing-point depression

Colligative properties can be sources of insight into not only the properties of solutions, but also the properties of the solute. For example, acetic acid, CH.COOH, behaves differently in two different solvents, (a) The freezing point of a 5.00% by mass aqueous acetic acid solution is — l.72°C. What is the molar mass of the solute Explain any discrepancy between the experimental and the expected molar mass, (b) The freezing-point depression associated with a 5.00% by mass solution of acetic acid in benzene is 2.32°C. Whar is the experimental molar mass of the solute in benzene What can you conclude about the nature of acetic acid in benzene ... 

Fig. 6. Concentration dependences of a apparent molecular weights ", and b freezing-point depression 6 per unit concentration c in benzene of poly(a-phenylethyl isocyanide) of Mn = 34800. [Reproduced from Ref. (21), with permission of J. Wiley and Sons, Publ.]...

Pure benzene freezes at 5.50°C and has a density of 0.876 g/mL. A solution of 1.7 g of nitrobenzene in 250 mL benzene freezes at 5.18°C. What is the molality-based freezing-point depression constant of benzene and at what temperature does a solution containing 3.2 g of bromobenzene in 250 mL of benzene freeze (You may make the ideally dilute approximation for both these solutions.)... 

The indirect measurement of the aqueous vapor pressure of capillary systems by freezing point depression of benzene." Proc. Roy. Soc. London, 106 (Ser. A) 233-242. 

A) 0.272 m. The molality is calculated as the number of moles of unknown per kilogram of benzene. Because the number of moles of the unknown substance is not known, the molality will be calculated from the freezing-point depression of the solution. This is done using the equation A7 = Kfm. Because the solution is a nonelectrolyte, the van t Hoff factor is unnecessary. This expression can be rearranged to yield A Tf = Kf = m. Molality is determined to be ... 

Characterization of the AlMe3—MeCl System by NMR. It appears that the AlMe3 in methyl chloride system has not been investigated previously by NMR spectroscopy. In related research by other workers, freezing point depression measurements of AlMe3 in benzene solution indicated the predominant presence of dimers—i.e. (13) ... 

The freezing point of the solution is equal to the freezing point of the solvent, pure benzene, minus the freezing-point depression (Atf) ... 

The dimer is relatively nonpolar and thus more soluble in benzene than in water. Since benzoic acid forms dimers in benzene, the effective solute particle concentration will be less than 1.0 molal. Therefore, the freezing-point depression would be less than 5.12°C (AT, = Kfm). 89. a. 26.6 kj/mol b. -657 kj/mol 91. 0.050... 

Nitric acid alone fails to nitrate benzene and sulfuric acid also does not readily react with it, yet the mixed acid is an efficient nitrating reagent. Solutions of nitric acid in sulfuric acid show an approximately four-fold molar freezing-point depression and this has been attributed to the generation of four ions, as shown in equation (1) ... 

The molecular weight of an organic compound was determined by measuring the freezing point depression of a benzene solution. A 0.500-g sample was dissolved in... 

A solution containing 4.22 g of a nonelectrolyte polymer per hter of benzene solution has an osmotic pressure of 0.646 torr at 20.0°C. (a) Calculate the molecular weight of the polymer, (b) Assume that the density of the dilute solution is the same as that of benzene, 0.879 g/mL. What would be the freezing point depression for this solution (c) Why are boiling point elevations and freezing point depressions difficult to use to measure molecular weights of polymers ... 

Pentaethoxyuranium is a dark-brown, mobile liquid with a density of 1.71 g/cm3 at 25°.2 The liquid boils at 123° at 0.001 torr and is thermally stable below 170°. The compound is readily hydrolyzed and is oxidized by dry oxygen (in the presence of excess NaOC2Hs) to hexaethoxyuranium.2 Pentaethoxyuranium has a dimeric structure at room temperature as determined by freezing-point depression measurements in benzene.2 It is miscible with ethanol, diethyl ether, benzene, petroleum ether, ethyl acetate, carbon tetrachloride, chloroform, carbon disulfide, pyridine, dioxane, and nitrobenzene. The proton magnetic... 

The molar mass of benzoic acid (CgH5COOH) determined by measuring the freezing-point depression in benzene is twice what we would expect for the molecular formula, C7H5O2. Explain this apparent anomaly. 

The freezing point depression constant for cyclohexane is 20.3, which is very high when compared to the 1.86 for water. You need 20-30 mL of pure material in order to make several measurements, and all you have available is some technical-grade material that was prepared by catalytic hydrogenation. You are to do an extractive distillation to remove the benzene impurity. 

Two grams of benzoic acid dissolved in 25 g of benzene, Xy = 4.90 Kkg/mol, produce a freezing-point depression of 1.62 K. Calculate the molar mass. Compare this with the molar mass obtained from the formula for benzoic acid, CgHjCOOH. 

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