Relative boiling points

Metal Purification. Depending on the relative boiling points, purification may be carried out by RE distHlation, aHoying element distHlation, or 2one melting. 

EXAMPLE 5.1 Predicting relative boiling points on the basis of dipole-dipole interactions... 

Cl l CH2CI 12CH2OCHv (a) Draw a Lewis structure for each molecule, name it, and classify it by functional group, (b) Which molecules are isomers of each other Are any chiral If so, which ones (c) For each molecule, list the types of intermolecular forces that are present, (d) Use your answers to parts (a) and (b) to predict the relative boiling points, from lowest to highest. 

If the relative boiling points of the components in the reactor product are considered, there is a wide range of volatilities. The sulfur dioxide, butadiene and n-butane are all... 

Once the hexane has been used for the oil extraction it will be removed and the oil isolated. Because of the relative boiling points of the hexane and the oil, it will be simple to remove the hexane by distillation. Whatever the grade of hexane used, inorganic impurities are likely to be insignificant and can be discounted. Organic impurities are likely to boil at temperatures close to hexane and can therefore also be removed from the oil by distillation. Thus, the Certified AR grade is suitable. 

Pressure has a marked effect on the azeotropic composition and vapor-liquid equilibrium diagrams of alcohol-ketone systems (J). This is due to the fact that the slopes of the vapor pressure curves of alcohols are appreciably greater than for ketones it results in an unusually larger change in the relative boiling points of the components of an alcohol-ketone system with change in pressure. 

Lecat (2) has devised an analytical method for determining azeotropic boiling points and compositions for certain related groups of binary systems. The method is based on the fact that the composition and boiling point of an azeotrope are related to the relative boiling points of the two components. 

To predict relative boiling points, we should look for differences in (1) hydrogen bonding, (2) molecular weight and surface area, and (3) dipole moments. Except for neopentane, these compounds have similar molecular weights. Neopentane is the lightest, and it is a compact spherical structure that minimizes van der Waals attractions. Neopentane is the lowest-boiling compound. 

To predict relative boiling points, look for differences in... 

Predict relative boiling points, acidities, and solubilities of alcohols and thiols. 

Draw and name ethers and heterocyclic ethers, including epoxides. Predict their Problems 14-30, 31, and 32 relative boiling points, solubilities, and solvent properties. 

To compare the properties of alkanes, alkenes, and alkynes, you will be working with compounds that have the same number of carbon atoms. First, you will construct and compare butane, trans-2-butene, 2-butyne, and cyclobutane. You will use a graph to compare the boiling points of each compound. Next, you will use what you have just observed to predict the relative boiling points of pentane, trans-2-pentene, 2-pentyne, and cyclopentane. You will construct and compare these structures and graph their boiling points. 

Predict the relative boiling points for these four compounds. Use a reference book to find and graph the actual boiling points. 

Table I shows that, as the boiling point of the hydrocarbon used as the entrainer increases so does that of the azeotrope with water and the percent of water therein. A high percentage of water in the azeotrope is desired for the heat required for the distillation, which is mainly that of the latent heat of the water plus that of the entrainer. Sufficient entrainer should be available in the azeotrope for reflux to the column although this requirement is not large. Also, the solubility or dilution effect is better with lower-boiling hydrocarbons. Thus there are several factors to be balanced in choosing the azeotrope. The effect of relative boiling points, vapor pressures, and amounts of different entrainers in their azeotropes with water has been discussed as affecting the choice of entrainers for separating water from acetic acid (5). However, that represents a much more difficult selection because there the quantity of reflux is important and also the solvent characteristics of the entrainer for the acetic acid also control the choice.

Predicting Make a prediction about the relative boiling points of the noble gases. Give a reason for your answer. 

Representative Physical Parameters for TPH Analytical Fractions Based on Correlation to Relative Boiling Point Index... 

Predict the relative boiling points of ammo-nia(NH3), phosphine (PH ), and arsine (AsHj). Explain your prediction. 

Relative Boiling-Point Temperatures and Strengths of Attractions... 

If you can predict the types of attractions between particles in two different substances, you can also predict the relative strengths of those attractions, and then the relative boiling-point temperatures for the substances. The textbook s Web site shows a general procedure for making these predictions. 

Contrast ionic and covalent compounds with respect to their relative boiling points. 

The acid properties of carboxylic acids have been discussed previously (Sections 1.18 and 7.10). Recall that carboxylic acids have values of approximately 3-5 (Appendix II see also Special Topics I in the Study Guide and Solutions Manual). The acid properties of dicarboxylic acids will be discussed in Section 17.21. The boiling points and other physical properties of carbonyl compounds are listed in Appendix I. Carbonyl compounds have the following relative boiling points ... 

Find an alkane, a ketone, and an alcohol with roughly the same MW (within 5 g/mole). Rank these compounds in terms of relative boiling points. 

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