Which of these collectively come under van der waals forces?

London dispersion forces and dipole-dipole interactions

Explanation:

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There are two intermolecular forces that are collectively referred to as Van der Waals Forces: London dispersion forces and dipole-dipole interactions.

London dispersion forces are the weakest intermolecular forces. They are temporary attractive forces that turn out when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles.

On the other hand, dipole-dipole interactions turn out when two dipolar molecules interact with each other through the containing space. In such a way, the partially negative portion of one of the polar molecules is attracted to the partially positive portion of the second polar molecule.

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yes the answer is total mass in unchanged   : )