Virtual Lab

Introduction:

All matter is made of molecules. What makes the molecules stick together? Intermolecular forces hold the molecules together. In some cases they are strong enough for molecules to be very close and in others they are relatively weak and molecules tend to fly away from each other. This is why we see different states of matter.

The intermolecular forces are mainly electric in nature. Electrons distribute themselves between and around the atomic nuclei such that in case of asymmetric bonds, there is a partial negative charge at one end and a partial positive charge at the other. For example, in molecules like HCl (Hydrogen Chloride), the electrons are closer to chlorine nucleus than the hydrogen nucleus, effectively creating a partial separation of charge. This is what is called a molecular dipole. A dipole may induce another dipole in a neighbouring molecule by attracting the electrons in the neighbour towards its positive end. Generally dipole-dipole interactions and dipole-induced dipole interactions make up for most of the intermolecular forces. Dipole moment is one of the keys towards understanding of phenomenon like solubility of substances and the states of matter.

A dipole is nothing but a system of two equal and opposite charges (+Q and -Q) kept at a separation (given by vector r). Permanent dipole moments are fixed relative to molecular axes. If the vector r points from the negative to the positive charge, the electric dipole is d = Qr. In the SI system of units, the unit of dipole moment is the coulomb-m. One typically finds molecular dipole moments reported in Debyes (D). [1 D = 1 x 10 ^-18 statcoulomb-cm =3.33564 x 10^-30 coulomb-meter].
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Virtual Lab

Quiz

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Objective:

To measure the dipole moment of gaseous and liquid substances using dipolemeter.

Manual:
1. Select the gaseous substance and the temperature at which dipole moment is to be measured.
2. Start the experiment and "tune" the frequency to get resonant audio output.
3. Note the dielectric constant values and calculate dipole moment from it.
4. Go to the next stage and select a liquid from the dropdown menu.
5. Tune the frequency to get a resonant audio output.
6. From the dielectric constant so obtained calculate the dipole moment.

Measurement of Dipole Moment

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International Institute of Information Technology, Hyderabad (IIIT-H)

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Earthquake Engg. (EERC)

Computational Natural Sciences & Bioinformatics (CCNSB)

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