exp29-d8-6-07 - Experiment 29 Physical Chemistry Laboratory...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Experiment 29 Physical Chemistry Laboratory Dipole Moment of Polar Molecules in Solution (revised 6//07) Introduction The object of this experiment is to determine the dipole moment of a polar compound (acetophenone or methyl benzoate) from measurements of the densities and dielectric constants of dilute solutions of the compound in cyclohexane. From this data and the refractive index of the polar compound, the dipole moment of these is obtained. Theory Be sure to read a relevant discussion of dipoles, refractive index and polarizability of molecules. *It is suggested to preserve reagents, the order of performance of this experiment should be:
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 1. dielectric determination, 2.density, and lastly 3. refractive index. Procedure Density Solutions of 1.0, 2.0, 3.0, 4.0, 5.0 and 7.0 mole percent of the polar compound in cyclohexane are provided. The densities of these solutions, and of pure cyclohexane and acetophenone are to be determined with a pycnometer . Pycnometers are volume-calibrated containers used to determine the density of liquids or solids. They are particularly convenient for determining the density of liquids. Fig.1 picnometer Calibration: Calibrate the pycnometer (accurately determine its volume) using distilled water as the standard (V = m/ ρ ). Use a CRC to get the density of distilled water at its measured temperature. Average at least three volume determinations. General Procedure: Record the mass of the empty pycnometer with the capillary stopper and thermometer in place. Fill the pycnometer with the liquid of interest and then place the thermometer and the capillary stopper in place; some of the liquid should overflow from the capillary. Using a Kimwipe, dry the outside of the pycnometer and then wipe the top of the capillary stopper clean. Record the mass and temperature of the filled pycnometer. To obtain the mass of the liquid, subtract the mass of the empty pycnometer from the mass of the filled pycnometer. Use the calibrated volume of the pycnometer and the mass of the liquid to determine the density of the liquid. It is important to thoroughly dry the picnometer when determining the empty volume. Use an aspirator and/or dry with acetone. Note: It is important to minimize the time it takes to measure the mass of the liquid-filled pycnometer. Consider the effects of evaporation from the capillary and the influence of your body's temperature on the liquid's temperature. Refractive index Fig. 2 Abbe refractometer The refractive index of either acetophenone or methyl benzoate is determined with an Abbe refractometer using light from a sodium vapor lamp. The Abbe refractometer is described on p.659 (Chapter XX) of Shoemaker, Garland, and Nibler, 6 th ed. [1] (see attachment). The refractive index should be measured for all molar solutions along with the pure liquids (e.g. cyclohexane and acetophenone).
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/17/2008 for the course CHEM 541/42 taught by Professor Allen during the Spring '07 term at Ohio State.

Page1 / 9

exp29-d8-6-07 - Experiment 29 Physical Chemistry Laboratory...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online