Somerepresentativeconstantsboilingpointsandfreezingpoi

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Unformatted text preview: is specific for each solvent, and m is the molality of the solution and is expressed as the number of moles of solute per kilogram of solvent. Some representative constants, boiling points, and freezing points are given in the table below. Solvent CH3CO2H (acetic acid) C6H6 (benzene) CHCl3 (chloroform) C2H5OH (ethyl alcohol) H2O (water) C10H8 (naphthalene) C6H12 (cyclohexane) C10H16O (camphor) C4H10O (t­butanol) Freezing Point (°C) 16.6 5.4 ­63.5 ­141 0.0 80.6 6.5 179 25.5 Kf (°C/m) 3.90 5.12 4.68 ­­­­ 1.86 6.9 20.0 39.7 9.1 Page 1 of 9 Boiling Point (°C) 118.1 80.2 61.3 78.4 100.0 218 81 208 ­­­­ Kb (°C/m) 2.93 2.53 3.63 1.22 0.512 5.65 2.79 5.95 ­­­ Chemistry 52 The equations relating the boiling point elevation and freezing point depression to molality are: ΔTb = Kb • m • i ΔTf = Kf • m • i where ΔTb and ΔTf are the change in boiling point and freezing point respectively, Kb and Kf are the boiling and freezing constants for a particular solvent, and i is the factor which is used to account for the number of particles a given solute generates in solution. Substances are usually classified as ionic or covalent, or more precisely, electrolytes and non electrolytes. Electrolytes dissolve in a solvent to give ions (charged particles) in solution while non electrolytes dissolve to give molecules. A mole of non electrolyte such as ethanol would dissolve to produce a mole of ethanol molecules. However, a mole of sodium chloride (NaCl) would dissolve...
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This document was uploaded on 03/18/2014 for the course CHEM 52 at Los Angeles Mission College.

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